开云体育

ctrl + shift + ? for shortcuts
© 2025 开云体育
  1. TekScopes
  2. Messages
Expanded Topics Messages Polls
Date
Re: probe.

 

On Thu, May 28, 2020 at 07:40 AM, James Theonas wrote:


Is this probe a good match for my scope?
It would be insofar as bandwidth is concerned. The transient response however is not matched to the input characteristics of the 2465B. It'll work but signal fidelity will not be optimal, resulting in visible step response artifacts. For the 2465B, Tek recommended the P6137. With the right tools and equipment, you could optimize the behavior of the probe with its high-frequency adjustments.

Raymond
Re: Trying to save a 576

 

Ryan, has that CRT been taken? If not, I would be interested, does the screen appear burned? My 576 works, but has a completely dead spot where the intensity was left too high with a static spot displayed.
Re: 576 collector supply issues

 

Wiring restored to original and now it's working. Going to go through the full test and cal procedures to see how it's behaving now.
Re: probe.

 

This is intended for use with some TDS scopes and has a 500MHz bandwidth. So probably ok with a 400MHz scope. They also have a problem which can render them scrap. See:

I don't have either a 2465B or a P6139A, so you can take this with a pinch of salt, except for the mentioned problem.
Colin.

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of James Theonas via groups.io
Sent: 28 May 2020 06:40
To: TekScopes Mail List (New: groups.io)
Subject: [TekScopes] probe.

A quick question for the group. I have a 2465b and have found a p6139a locally in good condition. Is this probe a good match for my scope?
Dimitris Theonas
Re: Tek 4041 GPIB Controller

 

Monty,

Good to see you have now established communication with the keyboard port. You are correct that the COMM0 port description is required for a 4041 with the dual RS232 port option.

I use the same technique since my tape drive doesn't work and I have to manually enter those commands every time the 4041 is powered up to redirect the console. I been thinking of automating the process by building a small microcontroller board that emulates the keyboard and outputs the necessary commands every time the 4041 is powered on. I haven't progressed this yet as I need to do some experiments to figure out when the 4041 has completed its power-up sequence and is ready to accept keyboard commands and how fast it can process those commands.

Stephen
Re: Encouraging beginners: What are we accomplishing?

 

Hello Dennis,

Denis Cobley was his name, I spelt it incorrectly.
If you look up the old messages you will find him.
In regards to test equipment repairs, Magic flowed
from his hands and he had an encyclopdiac knowledge of Tektronix scopes of that era.

The little company, "TrioSmartcal", where he was the service manager changed its name as it merged
and got absorbed by other companies. Over the years
all the people that I once knew have drifted away so I
do not know where Denis Cobley is today. One of the most helpful men I have ever known, I learnt a
lot from him.

More than a decade ago, thanks to this group, I met Denis Cobley and got a job when I needed one. That is something more than just luck!

Regards,
John Crighton
Sydney

----- Original Message -----
From: "Dennis Tillman W7pF" <dennis@...>
To: <[email protected]>
Sent: Thursday, May 28, 2020 2:17 PM
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?


Hi John
Thanks for the reply and the very interesting story.
I feel like I know Denis Cobly from somewhere.
I did a search of my email but didn't fine anything.
Would you ask him if he recognizes my name, and if so, from where,
Thanks, Dennis



---
This email has been checked for viruses by AVG.
Re: 475 questions

 

Hi All,

I may have done this, but I don't think so: /g/TekScopes/photo/247625/0?p=Created,,,20,2,0,0. Note the cap and resistor are supposed to be soldered to one another, but the joint was broken. I soldered the leads back together, but I think I need a cylindrical crimp fitting to reduce the chance that the joint will break there again.

Bruce
Re: 475 questions

 

Hi Barry,

That certainly looks like a neat way to handle it! I've already order the disc-shaped ones for this board. As far as I know, there isn't a similar set-up available for the 475, but I like the single board with stand-offs. My 475 has six large caps there, rather than five, although I read somewhere that two of these are in parallel, so can be replaced with a single cap. Was that solution a custom job, or purchased ready made?

Bruce

On Wed, May 27, 2020 at 08:03 AM, n4buq wrote:


I have hesitated to mention this as a possible approach to the filter caps in
the 475 because:

1. I don't know for sure whether the layouts between the 465 and 475 are
identical
2. The design is, well, a bit kludgy (if I do say so myself)

However, I thought I'd pass it along.

Pictured in this album is an implementation of a separate circuit board that
provides that ability to use common snap-in caps as replacements. My intent
for this was to make it possible to replace those caps again (should it every
become necessary) without further desoldering/soldering on the main board.

/g/TekScopes/album?id=64929

There are small disc adapters that do somewhat the same thing (I have some);
however, if a future cap replacement becomes necessary, I'm not sure it is
possible to do that without removing the disc which, of course, involves
solder work on the main board.

Maybe one day I'll afford a snazzy desoldering tool which would probably
(certainly?) make that part much easier for me but, for those large can
connections, it's not fun with a 25-year-old Radio Shack solder sucker. The
can, itself, is a rather large heat sink/spreader which further complicates
that process.

Anyway, FYI.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "VK1GVC" <vk1gvc@...>
To: [email protected]
Sent: Wednesday, May 27, 2020 9:40:45 AM
Subject: Re: [TekScopes] 475 questions

Bruce, I treat tantalums like I treat people - assume they have good
intentions unless I learn otherwise.? If you remove lots of them without
reasonable suspicion then you'll probably do more damage than good as
Eric has warned.? As tantalums usually fail to a short circuit, a
failed/shorted tantalum will pull down the voltage at that point to
close to zero and this will/should be straighforward to find - later.
At this stage, if I haven't missed any key points, you've found 2
sick/dead capacitors in the +50V supply which MAY be the cause of all
the wrong voltages you've measured in the low voltage power supply
section.? So replace those caps first, then adjust all of the LV power
supply to meet calibrations specs and see what happens.? You might have
a working scope if luck is very much with you, or you might be one step
on a long journey towards that goal.

And when you replace the tantalum which lost a leg, make sure you
install the new one with the right polarity.? Tantalums don't like
reverse voltage and they can get hot, emit smoke and explode.? I've seen
it happen when a workmate powered up some newly assembled eqpt for the
first time and heard a hissing sound so he bent down for a better look.
A cylindrical metal tube type tantalum then exploded and flew off the
PCB, burning itself onto the side of his neck. Very painful ... and the
language was terrible.? And very lucky he didn't get hit in an eye.

BTW here's a different type of tantalum which I don't think has been
mentioned yet - see the colourful little blob in the lower left of the
picture at this link:
/g/TekScopes/photo/12901/22?p=Name,,475,20,1,0,0

It has a black top, brown middle and green bottom ... the colours are a
derivative of the resistor colour code and I think there's a spot on one
side too.? Much better dressed than a plain boring tantalum!

Graham

On 27/05/2020 3:28 pm, ciclista41 via groups.io wrote:
Graham,

Well, my scope is peppered with the kind in the photo. Maybe they
re-spec'ed the caps later in production, or maybe the US Army bought
enough in their contract with Tek that they were able to spec what they
wanted. Mine is from November of 1982, if the date code on the AC power
cord box inside the case just above the transformer is original.

I went ahead and pulled the two tantalums out of the circuit to measure
them. I broke a lead off the first one, pulling too hard. Because I only
have access from the top of this A7 board unless I remove it, which I
don't want to do, my solder sucker wasn't able to slide over the clipped
end of the leads, and I had to just use a sharp tip on my iron. Did much
better on the second one, which came out easily by that second method. I
then used the sucker to remove the remaining solder from the holes in the
board for when I replace the broken one.

Yes, you were right to question my belief that they were bad. Out of
circuit, they both tested well within the green on my ESR tester. So much
for being able to reliably test capacitors in circuit with that thing.
They weren't even close to being in spec when tested with it in circuit.
I was thinking that these dipped tantalums were generally bad in boards
this old based on numerous threads in this forum and others saying how
often these were bad. Some said they routinely replace them all when they
see them in a scope of this era. I have tested dozens on this board and
only found about a handful that this tester considered bad. So,
considering that these two were among the worst that I tested in circuit,
I decided to pull them, as they'd be less easily accessible later when the
A8 board is back in place.

So this makes me question whether the tantalums in this board are among
the
infamous ones. I hope not, obviously. Your statement that my photo
showed what looked like a very '80's tantalum made me think maybe the
infamous ones are some earlier 60's or 70's version. How can I know,
other than pulling them all? At this point, I don't see the point of
pulling any of them unless they show up as faulty later, when there is a
trace on the scope and I can run it through its paces and make sure it's
working as it should.

Speaking of working as it should, Tektronics calls for several specialized
calibration tools in the manual. If the scope is running well, with no
serious issues other than calibration, can it be calibrated without
resorting to the purchase of such tools? I briefly noted some shops
wanting a couple of hundred dollars to calibrate a scope. Definitely
don't want to do that! If I thought I had to have someone else calibrate
it, I probably wouldn't have taken on the project and just invested in a
new digital scope.

Bruce

On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:

Bruce, the link to the pics on TekScopes worked for me and that
capacitor looks very 1980's tantalum as Michael confirmed in a later 475
manual and the Tek Common Parts manual.? Ceramics of that era were
commonly flat circular disks, very different from what you have.

Roger re testing in place - very problematic.? Best to remove them to
eliminate any ambiguity and as you have reported success in desoldering
then that's the best option while you have access.? BTW I'm curious to
know why you *believe* that they are faulty - mere suspicion based on
type and age, or something else?

You quoted your post of 22 May to Harvey a few minutes ago in which you
sought advice about what can and cannot be substituted when replacing
1982 components in 2020.? Has that qn been answered to your satisfaction
or is it still a live issue?? The short answer is: it depends.? The
long
answer really has to address a specific component in a specific
application.? But the laws of physics haven't changed a lot in the last
40 years so there is almost certainly something out there which can be
bought/found/made/adapted or cajoled to do the job.? If you need a 1amp
400V rectifier diode then a IN4004 of the 70's or 80's is just the same
as one from the factory today.? If you need a very specific high-spec
module made for or by Tek for a very challenging application 40 years
ago and now out of production ... oh dear, you've got a problem.
Fortunately we now have TekScopes, some wikis, eBay and of course the
WWW.

Graham

On 27/05/2020 1:24 pm, ciclista41 via groups.io wrote:
Hi Graham,

I posted a photo of the C1091 tantalum, along with the plaque stuck to
the
back of my scope here:
/g/TekScopes/album?id=247625&p=Created,,,20,2,0,0

Bruce


--
This email has been checked for viruses by Avast antivirus software.
Re: 475 questions

 

Hi Michael,

I had noticed that page of the manual in passing, but did not study it, as I assumed it would be following the same standard used elsewhere. Thank you for pointing out that that is not the case. I now have that page printed for easier reference in the future and have verified the correct cap rating using it as you describe. The diagram also shows the vertical stripe as indicating the positive lead. However, as you indicated, the voltage rating corresponding to the gray color of the vertical stripe is not designated in the chart. If we call it silver, rather than gray, the chart remains ambiguous as to voltage rating. I assume that since the C1304 is supposed to be 50V ±20 that that is what it is. As you said, no way to tell by looking at the capacitor, itself, though.

How did you know what voltage is being used by the circuit on the A7 board?

Bruce
Re: 475 questions

 

Hi Michael,

Very good to hear that Tek has that convention, as it confirms what I thought about how these were oriented before I took them out. Experience is so very valuable when it comes to this kind of thing. Thank you very much for sharing yours!

Bruce

On Wed, May 27, 2020 at 07:24 PM, Mlynch001 wrote:


Bruce,

The square pad is TEKs way of designating the positive side of any polarized
device. So Yes, square pad is + side of the Capacitor. This also applies to
diodes as well. Sometimes Tek will use the square pad to designate the number
one pin of an IC, however, this is not universally true. The number one pin
can also be designated by a small round dot on the PC board, adjacent to the
pad. The number one pad is sometimes not identified in any manner. My
experience is working many of these 4xx Series as well as other contemporary
Tektronix instruments. This holds true on almost all the instruments that I
have personally repaired. I do not always depend on the color codes on these
caps, I tend to rely on the values stated in the schematics and in the parts
list. One thing that I try to do is take a picture of the area of the board
where I am working, BEFORE I make any changes and I try to document exactly
these sort of markings for later reference.
--
Michael Lynch
Dardanelle, AR
Re: 475 questions

 

Hi Graham,

I've taken several photos, particularly of the A8 board that I removed to get at the large caps. Forgot to do that with the A7 board, but I noted that the printing on the cap was facing the front of the scope before removal, so got away with the oversight this time.

Yes, that colorful sleeping dog will remain undisturbed!

Bruce

On Wed, May 27, 2020 at 06:59 PM, VK1GVC wrote:


Bruce, the + sign is unambiguous, that lead is definitely the postive
lead.? The 'bent knee' lead may be the + lead but I am not aware of that
as a convention so trust the markings.? Likewise the square solder pad
may be a Tek convention (can other readers comment?) but I am not aware
of it so I wouldn't rely on it.? Not having access to a 475 I can't get
a good look at the A7 board and the image of the PCB layout, Fig 7-16 in
the manual is very grainy and I can't see the shape of these pads.? The
best way to confirm which way around these tantalums should be is by
looking at the pics you took of the board before you removed them!? Yes
I forget to do that too, but it's very helpful in these circumstances.?
I did refer to the pic of C1091 you posted but the focus is a bit off
where it's needed.? I *think* the + is on the left as that looks like
the 'bent knee' lead but I'm not certain.

The next best way is to identify nearby components and find which
connects to which, and the schematic shows those two ferrite bead
inductors L1091 and L1093 and they tell the story.? Note that supply
rail to L1091 and C1091 is negative and the other L and C are on a
postive supply rail so the capacitor polarity will reflect that.

As for the colourful tantalum on the A9 board, I worked out the colour
code as you did and I can't explain the difference with the parts list.?
That could be a wild goose chase all of its own so unless you have
reason so suspect its motives, I think the sleeping dog principle applies.

Graham

On 28/05/2020 9:43 am, ciclista41 via groups.io wrote:
Hi Graham,

I try to treat people that way, too. After my brief adventure with C1091
and C1093, I'm doing the same with tantalum caps in this scope.

The leads on this tantalum are not symmetrical to the body. If you look at
them as legs on a body, one seems to have a knee bent out to the side rather
than dropping straight to the floor. There is a + sign printed closer to that
leg. I'm guessing that's the positive lead. The through holes they came out
of have a square trace pad and a round trace pad. I'm guessing these are to
guide polarity. I think the positive leg went to the square, while the
negative went to the round, but I'm not absolutely sure of that.
Confirmation? Is this a standardized thing?

At /g/TekScopes/photo/247625/0?p=Created,,,20,2,0,0, you'll
see an even more colorful one I found on my A9 board. Who knew these scopes
were wearing jewelry when no one was looking?

According to this chart:
, that's
a Red=2, Violet=7, Grey=.01 multiplier, Green = 16V.
So that's .27μF, right? But the manual says this is a 196D275X9050JA1 or a
290-0573-00. The latter is listed in the Tektronix Common Parts Catalog as
2.7μF, 50V. What am I not getting?

Bruce

On Wed, May 27, 2020 at 07:40 AM, VK1GVC wrote:

Bruce, I treat tantalums like I treat people - assume they have good
intentions unless I learn otherwise.? If you remove lots of them without
reasonable suspicion then you'll probably do more damage than good as
Eric has warned.? As tantalums usually fail to a short circuit, a
failed/shorted tantalum will pull down the voltage at that point to
close to zero and this will/should be straighforward to find - later.
At this stage, if I haven't missed any key points, you've found 2
sick/dead capacitors in the +50V supply which MAY be the cause of all
the wrong voltages you've measured in the low voltage power supply
section.? So replace those caps first, then adjust all of the LV power
supply to meet calibrations specs and see what happens.? You might have
a working scope if luck is very much with you, or you might be one step
on a long journey towards that goal.

And when you replace the tantalum which lost a leg, make sure you
install the new one with the right polarity.? Tantalums don't like
reverse voltage and they can get hot, emit smoke and explode.? I've seen
it happen when a workmate powered up some newly assembled eqpt for the
first time and heard a hissing sound so he bent down for a better look.
A cylindrical metal tube type tantalum then exploded and flew off the
PCB, burning itself onto the side of his neck. Very painful ... and the
language was terrible.? And very lucky he didn't get hit in an eye.

BTW here's a different type of tantalum which I don't think has been
mentioned yet - see the colourful little blob in the lower left of the
picture at this link:
/g/TekScopes/photo/12901/22?p=Name,,475,20,1,0,0

It has a black top, brown middle and green bottom ... the colours are a
derivative of the resistor colour code and I think there's a spot on one
side too.? Much better dressed than a plain boring tantalum!

Graham

On 27/05/2020 3:28 pm, ciclista41 via groups.io wrote:
Graham,

Well, my scope is peppered with the kind in the photo. Maybe they
re-spec'ed the caps later in production, or maybe the US Army bought enough
in
their contract with Tek that they were able to spec what they wanted. Mine
is
from November of 1982, if the date code on the AC power cord box inside the
case just above the transformer is original.
I went ahead and pulled the two tantalums out of the circuit to measure
them. I broke a lead off the first one, pulling too hard. Because I only
have access from the top of this A7 board unless I remove it, which I don't
want to do, my solder sucker wasn't able to slide over the clipped end of
the
leads, and I had to just use a sharp tip on my iron. Did much better on
the
second one, which came out easily by that second method. I then used the
sucker to remove the remaining solder from the holes in the board for when
I
replace the broken one.
Yes, you were right to question my belief that they were bad. Out of
circuit, they both tested well within the green on my ESR tester. So much
for
being able to reliably test capacitors in circuit with that thing. They
weren't even close to being in spec when tested with it in circuit. I was
thinking that these dipped tantalums were generally bad in boards this old
based on numerous threads in this forum and others saying how often these
were
bad. Some said they routinely replace them all when they see them in a
scope
of this era. I have tested dozens on this board and only found about a
handful
that this tester considered bad. So, considering that these two were among
the worst that I tested in circuit, I decided to pull them, as they'd be
less
easily accessible later when the A8 board is back in place.
So this makes me question whether the tantalums in this board are among
the
infamous ones. I hope not, obviously. Your statement that my photo showed
what looked like a very '80's tantalum made me think maybe the infamous
ones
are some earlier 60's or 70's version. How can I know, other than pulling
them all? At this point, I don't see the point of pulling any of them
unless
they show up as faulty later, when there is a trace on the scope and I can
run
it through its paces and make sure it's working as it should.
Speaking of working as it should, Tektronics calls for several specialized
calibration tools in the manual. If the scope is running well, with no
serious issues other than calibration, can it be calibrated without
resorting
to the purchase of such tools? I briefly noted some shops wanting a couple
of
hundred dollars to calibrate a scope. Definitely don't want to do that!
If I
thought I had to have someone else calibrate it, I probably wouldn't have
taken on the project and just invested in a new digital scope.
Bruce

On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:

Bruce, the link to the pics on TekScopes worked for me and that
capacitor looks very 1980's tantalum as Michael confirmed in a later 475
manual and the Tek Common Parts manual.? Ceramics of that era were
commonly flat circular disks, very different from what you have.

Roger re testing in place - very problematic.? Best to remove them to
eliminate any ambiguity and as you have reported success in desoldering
then that's the best option while you have access.? BTW I'm curious to
know why you *believe* that they are faulty - mere suspicion based on
type and age, or something else?

You quoted your post of 22 May to Harvey a few minutes ago in which you
sought advice about what can and cannot be substituted when replacing
1982 components in 2020.? Has that qn been answered to your satisfaction
or is it still a live issue?? The short answer is: it depends.? The
long
answer really has to address a specific component in a specific
application.? But the laws of physics haven't changed a lot in the last
40 years so there is almost certainly something out there which can be
bought/found/made/adapted or cajoled to do the job.? If you need a 1amp
400V rectifier diode then a IN4004 of the 70's or 80's is just the same
as one from the factory today.? If you need a very specific high-spec
module made for or by Tek for a very challenging application 40 years
ago and now out of production ... oh dear, you've got a problem.
Fortunately we now have TekScopes, some wikis, eBay and of course the
WWW.

Graham

On 27/05/2020 1:24 pm, ciclista41 via groups.io wrote:
Hi Graham,

I posted a photo of the C1091 tantalum, along with the plaque stuck to
the
back of my scope here:
/g/TekScopes/album?id=247625&p=Created,,,20,2,0,0

Bruce


--
This email has been checked for viruses by Avast antivirus software.
probe.

 

A quick question for the group. I have a 2465b and have found a p6139a locally in good condition. Is this probe a good match for my scope?
Dimitris Theonas
Re: Encouraging beginners: What are we accomplishing?

 

Hi John
Thanks for the reply and the very interesting story.
I feel like I know Denis Cobly from somewhere.
I did a search of my email but didn't fine anything.
Would you ask him if he recognizes my name, and if so, from where,
Thanks, Dennis

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Crighton
Sent: Wednesday, May 27, 2020 8:31 PM
To: [email protected]
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?

Double Yikes!

Hello Dennis,

thanks for the huge reply, I feel bad that you have spent many hours on it.
I have received your message loud and clear.
Good to know that you and Chuck are still mates, he did explain that in another post.

Dennis, please continue to run the group. I did not intend to undermine you.
I was just mentioning something that annoyed me. The abrupt end of Chuck's explaination of how to measure Xc using a scope. Just when his electronics lesson was getting interesting the whole discussion was stopped.
OK, I accept your reasons.

You said,
"TekScopes is about classic Tektronix test equipment, its use, repair, and collecting".
I believe in that too.
About 15 or 16 years ago, on this group, I asked some dumb questions about the air filter or lack of one, on my newly aquired 454 oscilloscope.
Someone in the USA offered to send me some filter material. How Generous!
A Mr. Denis Cobly, an ex Tektronix employee piped up on this group and said he was in Sydney also and I should call into "Trio Smartcal" and pick up filter material rather than let a Tekscope group member in USA send it to me.
I found out that "Smartcal" was a little company set up by ex Tektronix workers when Tektronix folded in Sydney. Some time later the name changed to Trio Smartcal.
I got to know Mr Denis Cobly by asking dumb questions and buying junked items.
Out of the blue one day he offered me a temporay job. I was in heaven, surrounded by Tektronix people and Tektronix equipment. Mr Denis Cobly explained that I was to look after "the junk" leaving his experienced boys to the more complex items that came in for repair and calibration.
One day a 475 scope landed on my bench. It came in a specially built Aluminium container with Qantas Airline calibration labels on it. It was in mint condition, no signs of use. I was given a check list to test the scopes performance but no adjustments to be made. It was explained that this scope was priceless as the aircraft makers specified this particular model 475 had to be used.
Like I said before, I was in heaven.
The ex Tektronix engineers around me were so helpfull in teaching me how to use the TM500 series instruments used to check this 475 scope.
Dennis, repair of old test equipment and learning along the way is what I like to do.
Bruce is struggling to repair his 475 scope on the "475 questions thread"
Ex Tektronix people helped me with a 475 scope years ago.
I support Bruce in fixing his 475 scope even though the thread is long and boring to some people on the group.
I hope I have explained where I am coming from.

Regards,
John Crighton
Sydney



----- Original Message -----
From: "Dennis Tillman W7pF" <dennis@...>
To: <[email protected]>
Sent: Thursday, May 28, 2020 10:54 AM
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?


YIKES!
Hi John,
I would like to make amends for anything I said to Chuck. I have known him
as a contributor to TekScopes for the past 17 years. I consider myself
fortunate that he has shared his experience and observations as a member of
other groups with me. We communicate with each other regularly off list. He
was planning to stop for a visit until the virus put everything on hold.
Only Chuck can say if your characterization is correct. Chuck is not shy so
if he has something to say I know he will :)

If possible put yourself in my shoes for a minute. Two weeks ago on
TekScopes several important issues were conflated and I was suddenly feeling
a lot of stress while I tried to sort out how best to proceed. The ESR Meter
thread resurfaced once again and I requested that the participants consider
the impact on our other members if they continued. I find it ironic that you
just clearly expressed your preference that the recent 475 thread be allowed
to continue ad infinitum by taking issue with Roy Thistle. You singled out
the one individual who, like you with the 475 thread, was a participant in
the lengthy ESR thread until Roy took charge of the issue by creating a new
ESR Forum on 开云体育. That relieved some of the pressure I was feeling
from members. Once again, Thank You Roy!

Some members saw ESR Meters as a legitimate Tek related topic since they are
a troubleshooting tool. Other members thought this topic was not specific
enough to TekScopes and requested I stop it. My responsibility is to choose
between them. Fortunately I didn't have to because Roy Thistle took charge
and created an ESR Forum on 开云体育.

Chuck and I have both been around long enough to remember teletypes. So it
was not really an issue when I saw the "character sketch" he included in an
email describing own to make an engineer's ESR Meter. I watched as one
member after another asked what that pile of hieroglyphics was supposed to
be. A few people understood it and provided an explanation. The explanations
resulted in still more questions/confusion which required even longer
explanations. Chuck and I both find it strange that something so simple
could cause so much confusion. I realized everyone needed instructions on
how to decipher it. So I provided the instructions to understand what Chuck
had drawn.

The issue of allowing attachments generated a lot of polarized responses pro
and con. Some of the responses were verging on rude which surprised me. I
have no experience with attachments and out of personal ignorance I thought
about all the things that could go wrong. I needed to learn more about
attachments ASAP and I started to do just that. I think Chuck must have
sensed I was confused and having a hard time with this because he contacted
me and made many good suggestions about where I should go and who I could
discuss my concerns with to learn more. Attachments have benefits and they
have drawbacks. I have seen some of the benefits. I am still waiting for
answers about how to eliminate or minimize the drawbacks.

I spent many hours today writing this reply to you (this is the third time I
wrote it, starting over from the beginning each time) because a brand new
issue appeared yesterday which has all the makings of a controversy that is
going to be a whopper. A few days ago I couldn't help but notice the "475
Questions" thread was getting very long. It is currently at 148 posts. I
took a look at a few of the posts and I was stunned to see a member ask what
"exp" meant. I couldn't spend much time thinking about it because yesterday
a member got right to the core of that issue when he posted this new topic
"Encouraging beginners: What are we accomplishing?" Apparently his question
is not easy to answer to everyone's satisfaction.

One more thing before I'll permit you to step out of my shoes:
All of these issues have generated a lot of comments that are taking a huge
amount of my time to respond to. That is less time I have to get the answers
to the whether to enable attachments I have asked of other group
moderator/owners. That was the hot issue 2 weeks ago. That is how far behind
I am. I will probably choose to ignore this new topic until I reach a
conclusion on the previous hot topic. Out of necessity I may stop responding
entirely until I catch up.
If you, John, would like to take my place in the interim please feel free.
A few things to remember if you do:
TEKSCOPES GOAL (from Michael Dunn in 2000): "TekScopes is about classic
Tektronix test equipment, its use, repair, and collecting".

THE GOLDEN RULE FOR GROUPS (from Stefan Trethan in 2018): “No politics, no
religion, no sports, simple as that.”

THE MODERATORS JOB IS TO STOP THIS PATTERN BEFORE IT REACHES #5
1. A slightly OT post is made.
2. It generates an unusually large number of responses.
3. This generates even more comments that go off at tangents.
4. Someone asks that the participants bring it under control.
5. That request creates more posts in support of the original slightly O.T.
post.
6. Someone replies with "if you don't like it use your delete key"
7. That results in comments pro and con about whether the original post was
O.T.
8. The posts die down over the next week.
9. If they don't die down the moderator will ask that the topic be put to
bed.

TEKSCOPES IS NOT A SALES SITE: EBay, Craigslist, etc. are the proper place
to list items you have for sale. However if you are offering our members
scarce parts, sub-assemblies, instruments, etc. at prices that our members
can afford then it makes perfect sense to offer them on TekScopes.

Dennis Tillman W7pF

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John
Crighton
Sent: Tuesday, May 26, 2020 10:04 PM
To: [email protected]
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?

Hello Roy,

I am really surprised at you of all people sounding like a wet blanket.

The owner of this tekscope group told you in no uncertain terms if you want
to talk about ESR Meters to go and form your own group. Which to your credit
you did just that. I also did not like the way that the owner of this
group, Dennis Tillman, jumped on Mr Chuck Harris for describing how to use
an oscilloscope with a function generator to check capacitors for value and
ESR. Shutting someone up for describing how to use an oscilloscope on an
oscilloscope group is to me just plain crazy.
Those are rules that you have to obey, like them or not.

Roy, if you are not enjoying reading about the repair of the 475 scope
by a beginner then do not read the thread. It is that simple!

I think it is marvellous that so many people on this group are willing
to help an individul fix his 475 scope. What a great thing to do,
while we are in corona virus lock down.
My fellow countryman Graham VK1GVC, down in Canberra is doing a great job
helping Bruce and so so are all the othere people.
The side benefit for me and no doubt others on this group is that Bruce is
asking basic questions as a beginner that other people on this group might
not dare to ask for fear of looking foolish.

Keep asking questions Bruce. I want you to fix this scope.

Regards,
John Crighton
Sydney


----- Original Message -----
From: "Roy Thistle" <roy.thistle@...>
To: <[email protected]>
Sent: Wednesday, May 27, 2020 1:51 PM
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?


Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just
what are TekScopers accomplishing with threads like this... and why are we
encouraging someone who is "... new to electronics..." to dig into a 475?..
one of the most complex, and compact, analog instruments ever designed.
I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson
super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere
the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got
a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take the
475 to someone who knows what they are doing... drop another 100.00 on it..
and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a
very fine instrument, with a double insulated power supply... and way
overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after parting
with some scarce cash... or finding some Tek picked apart in a basement
somewhere, where its been languishing for a generation...I've witnessed the
havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine...
just PM me to do it. I can't promise I'll reply to that... but, I'll read
your message.
Best regards and wishes.
Roy




---
This email has been checked for viruses by AVG.







--
Dennis Tillman W7pF
TekScopes Moderator








--
Dennis Tillman W7pF
TekScopes Moderator
Re: Encouraging beginners: What are we accomplishing?

 

Double Yikes!

Hello Dennis,

thanks for the huge reply, I feel bad that you have spent many hours on it.
I have received your message loud and clear.
Good to know that you and Chuck are still mates, he did explain that in
another post.

Dennis, please continue to run the group. I did not intend to undermine you.
I was just mentioning something that annoyed me. The abrupt end of Chuck's
explaination of how to measure Xc using a scope. Just when his electronics
lesson was getting interesting the whole discussion was stopped.
OK, I accept your reasons.

You said,
"TekScopes is about classic Tektronix test equipment, its use, repair, and collecting".
I believe in that too.
About 15 or 16 years ago, on this group, I asked some dumb questions about
the air filter or lack of one, on my newly aquired 454 oscilloscope.
Someone in the USA offered to send me some filter material. How Generous!
A Mr. Denis Cobly, an ex Tektronix employee piped up on this group and said he
was in Sydney also and I should call into "Trio Smartcal" and pick up filter material
rather than let a Tekscope group member in USA send it to me.
I found out that "Smartcal" was a little company set up by ex Tektronix workers
when Tektronix folded in Sydney. Some time later the name changed to Trio Smartcal.
I got to know Mr Denis Cobly by asking dumb questions and buying junked items.
Out of the blue one day he offered me a temporay job. I was in heaven, surrounded
by Tektronix people and Tektronix equipment. Mr Denis Cobly explained that
I was to look after "the junk" leaving his experienced boys to the more complex
items that came in for repair and calibration.
One day a 475 scope landed on my bench. It came in a specially built Aluminium
container with Qantas Airline calibration labels on it. It was in mint condition,
no signs of use. I was given a check list to test the scopes performance but
no adjustments to be made. It was explained that this scope was priceless
as the aircraft makers specified this particular model 475 had to be used.
Like I said before, I was in heaven.
The ex Tektronix engineers around me were so helpfull in teaching me how
to use the TM500 series instruments used to check this 475 scope.
Dennis, repair of old test equipment and learning along the way is what I
like to do.
Bruce is struggling to repair his 475 scope on the "475 questions thread"
Ex Tektronix people helped me with a 475 scope years ago.
I support Bruce in fixing his 475 scope even though the thread is long
and boring to some people on the group.
I hope I have explained where I am coming from.

Regards,
John Crighton
Sydney

----- Original Message -----
From: "Dennis Tillman W7pF" <dennis@...>
To: <[email protected]>
Sent: Thursday, May 28, 2020 10:54 AM
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?


YIKES!
Hi John,
I would like to make amends for anything I said to Chuck. I have known him as a contributor to TekScopes for the past 17 years. I consider myself fortunate that he has shared his experience and observations as a member of other groups with me. We communicate with each other regularly off list. He was planning to stop for a visit until the virus put everything on hold. Only Chuck can say if your characterization is correct. Chuck is not shy so if he has something to say I know he will :)

If possible put yourself in my shoes for a minute. Two weeks ago on TekScopes several important issues were conflated and I was suddenly feeling a lot of stress while I tried to sort out how best to proceed. The ESR Meter thread resurfaced once again and I requested that the participants consider the impact on our other members if they continued. I find it ironic that you just clearly expressed your preference that the recent 475 thread be allowed to continue ad infinitum by taking issue with Roy Thistle. You singled out the one individual who, like you with the 475 thread, was a participant in the lengthy ESR thread until Roy took charge of the issue by creating a new ESR Forum on 开云体育. That relieved some of the pressure I was feeling from members. Once again, Thank You Roy!

Some members saw ESR Meters as a legitimate Tek related topic since they are a troubleshooting tool. Other members thought this topic was not specific enough to TekScopes and requested I stop it. My responsibility is to choose between them. Fortunately I didn't have to because Roy Thistle took charge and created an ESR Forum on 开云体育.

Chuck and I have both been around long enough to remember teletypes. So it was not really an issue when I saw the "character sketch" he included in an email describing own to make an engineer's ESR Meter. I watched as one member after another asked what that pile of hieroglyphics was supposed to be. A few people understood it and provided an explanation. The explanations resulted in still more questions/confusion which required even longer explanations. Chuck and I both find it strange that something so simple could cause so much confusion. I realized everyone needed instructions on how to decipher it. So I provided the instructions to understand what Chuck had drawn.

The issue of allowing attachments generated a lot of polarized responses pro and con. Some of the responses were verging on rude which surprised me. I have no experience with attachments and out of personal ignorance I thought about all the things that could go wrong. I needed to learn more about attachments ASAP and I started to do just that. I think Chuck must have sensed I was confused and having a hard time with this because he contacted me and made many good suggestions about where I should go and who I could discuss my concerns with to learn more. Attachments have benefits and they have drawbacks. I have seen some of the benefits. I am still waiting for answers about how to eliminate or minimize the drawbacks.

I spent many hours today writing this reply to you (this is the third time I wrote it, starting over from the beginning each time) because a brand new issue appeared yesterday which has all the makings of a controversy that is going to be a whopper. A few days ago I couldn't help but notice the "475 Questions" thread was getting very long. It is currently at 148 posts. I took a look at a few of the posts and I was stunned to see a member ask what "exp" meant. I couldn't spend much time thinking about it because yesterday a member got right to the core of that issue when he posted this new topic "Encouraging beginners: What are we accomplishing?" Apparently his question is not easy to answer to everyone's satisfaction.

One more thing before I'll permit you to step out of my shoes:
All of these issues have generated a lot of comments that are taking a huge amount of my time to respond to. That is less time I have to get the answers to the whether to enable attachments I have asked of other group moderator/owners. That was the hot issue 2 weeks ago. That is how far behind I am. I will probably choose to ignore this new topic until I reach a conclusion on the previous hot topic. Out of necessity I may stop responding entirely until I catch up.
If you, John, would like to take my place in the interim please feel free. A few things to remember if you do:
TEKSCOPES GOAL (from Michael Dunn in 2000): "TekScopes is about classic Tektronix test equipment, its use, repair, and collecting".

THE GOLDEN RULE FOR GROUPS (from Stefan Trethan in 2018): “No politics, no religion, no sports, simple as that.”

THE MODERATORS JOB IS TO STOP THIS PATTERN BEFORE IT REACHES #5
1. A slightly OT post is made.
2. It generates an unusually large number of responses.
3. This generates even more comments that go off at tangents.
4. Someone asks that the participants bring it under control.
5. That request creates more posts in support of the original slightly O.T. post.
6. Someone replies with "if you don't like it use your delete key"
7. That results in comments pro and con about whether the original post was O.T.
8. The posts die down over the next week.
9. If they don't die down the moderator will ask that the topic be put to bed.

TEKSCOPES IS NOT A SALES SITE: EBay, Craigslist, etc. are the proper place to list items you have for sale. However if you are offering our members scarce parts, sub-assemblies, instruments, etc. at prices that our members can afford then it makes perfect sense to offer them on TekScopes.

Dennis Tillman W7pF

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of John Crighton
Sent: Tuesday, May 26, 2020 10:04 PM
To: [email protected]
Subject: Re: [TekScopes] Encouraging beginners: What are we accomplishing?

Hello Roy,

I am really surprised at you of all people sounding like a wet blanket.

The owner of this tekscope group told you in no uncertain terms if you want to talk about ESR Meters to go and form your own group. Which to your credit you did just that. I also did not like the way that the owner of this group, Dennis Tillman, jumped on Mr Chuck Harris for describing how to use an oscilloscope with a function generator to check capacitors for value and ESR. Shutting someone up for describing how to use an oscilloscope on an oscilloscope group is to me just plain crazy.
Those are rules that you have to obey, like them or not.

Roy, if you are not enjoying reading about the repair of the 475 scope
by a beginner then do not read the thread. It is that simple!

I think it is marvellous that so many people on this group are willing
to help an individul fix his 475 scope. What a great thing to do,
while we are in corona virus lock down.
My fellow countryman Graham VK1GVC, down in Canberra is doing a great job helping Bruce and so so are all the othere people.
The side benefit for me and no doubt others on this group is that Bruce is asking basic questions as a beginner that other people on this group might not dare to ask for fear of looking foolish.

Keep asking questions Bruce. I want you to fix this scope.

Regards,
John Crighton
Sydney


----- Original Message -----
From: "Roy Thistle" <roy.thistle@...>
To: <[email protected]>
Sent: Wednesday, May 27, 2020 1:51 PM
Subject: [TekScopes] Encouraging beginners: What are we accomplishing?


Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder.. just
what are TekScopers accomplishing with threads like this... and why are we
encouraging someone who is "... new to electronics..." to dig into a 475?...
one of the most complex, and compact, analog instruments ever designed.
I suppose.. in consideration... Michael discouraged the use of a Mr. Carlson
super Weller-kluge special, on the 475's pcb(s)... but, ya know... somewhere
the thread... the 475 owner hints he paid 20.00 for 475?, and he's also got
a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take the
475 to someone who knows what they are doing... drop another 100.00 on it...
and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a
very fine instrument, with a double insulated power supply... and way
overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after parting
with some scarce cash... or finding some Tek picked apart in a basement
somewhere, where its been languishing for a generation...I've witnessed the
havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well fine...
just PM me to do it. I can't promise I'll reply to that... but, I'll read
your message.
Best regards and wishes.
Roy




---
This email has been checked for viruses by AVG.







--
Dennis Tillman W7pF
TekScopes Moderator
Re: 475 questions

 

According to this chart: , that's a >Red=2, Violet=7, Grey=.01 multiplier, Green = 16V.
So that's .27μF, right? But the manual says this is a 196D275X9050JA1 or a 290-0573-00. The latter is listed >in the Tektronix Common Parts Catalog as 2.7μF, 50V. What am I not getting?
Bruce,

The chart that many people find in a Google search does not cover three band caps correctly. Refer to the TEKTRONIX manual to find the CORRECT method to decode the Tektronix marking system. Their system varies from the so called “standard” system. This leads to errors and misunderstandings.

This cap can be read correctly as below, colors indicate this:

Red = 2
Violet =7
Green= 5. Multiplier in picofarads

Therefore, this is 27followed by 5 zeros. This indicates the capacitance in pico faraday 2700000 pF =2.7uF.

So using this method, this one appears correct and agrees with the parts listing.

The TEKTRONIX marking method for these caps always designates voltage and tolerance using vertical paint daubs or stripes on the side of the cap body. Capacitance is always designated with the horizontal bands.

AGAIN, refer to the TEK manual for a detailed explanation of their marking methods.

I found that Tek typically places the vertical paint daubs on the positive side of the capacitor.

Many Tantalum caps do not have a voltage designator band. This one is supposed to be 50V, according to the parts list. That Voltage Value can usually be derived indirectly from the known operating voltage of the circuit. In this case, common sense tells us this cannot be a 16V cap, since it is operating in a circuit using a higher voltage than 16V. You would want to replace this with one of at least the same or greater voltage rating.


--
Michael Lynch
Dardanelle, AR
Re: Encouraging beginners: What are we accomplishing?

Chuck Harris
 

Hi Dennis,

We're good.

In a fit of pique, I mentioned leaving, because I wasn't here to
be scolded. It wasn't that you scolded me, but rather you scolded
a topic I was involved with. And to call you a scold is pretty
hyperbolic.

I'm an engineer, I could argue for weeks about why I was right and
you were wrong... and I could argue for weeks about why I was wrong
and you were right.

It really doesn't matter.

Like most here, I am rather tired of being dictated to about my health
habits, and whether or not I am the the reincarnation of Typhoid Mary.

Peace to all, and let's keep buggering on!

-Chuck Harris

Dennis Tillman W7pF wrote:

YIKES!
Hi John,
I would like to make amends for anything I said to Chuck. I have known him as a contributor to TekScopes for the past 17 years. I consider myself fortunate that he has shared his experience and observations as a member of other groups with me. We communicate with each other regularly off list. He was planning to stop for a visit until the virus put everything on hold. Only Chuck can say if your characterization is correct. Chuck is not shy so if he has something to say I know he will :)
Re: Encouraging beginners: What are we accomplishing?

 

My experience with Tektronix began far before I had a Tek scope. I was
about 11 years old and saw advertisements in Scientific American for
Tektronix oscilloscopes. I wanted a catalog to learn more about them. I
wrote a letter to Tektronix (I believe it was to the HQ in Beaverton)
asking for a catalog. Whoever received it must have figured out I was a kid
- no company name or address and clearly a home address. I think my English
was reasonable.

A few weeks later, a catalog showed up in the mail. I never forgot how well
they treated me. They could have disregarded that letter, but they were
nice enough to fulfill my request. As a result, when I had the chance to
recommend a replacement scope for a lab I was working in (I was the only
one with any electronics experience at all and it was mostly self-taught) I
asked them what they wanted to use it for. I don't recall the model I
suggested but I remember they wanted a high-gain differential amplifier. I
believe it must have been a 560-series with a 2A61 vertical amplifier. This
was long before the 7000-series and the 7A22. They were looking at low
voltage, low-frequency bioelectric signals. They had preamplifiers if they
needed them and Faraday chambers for single neuron work. So, Tektronix got
a purchase order based on my memory of how well they treated me. It was a
few years later that I acquired the 500-series scopes (DoD surplus) that we
used in the lab.

I will say that Hewlett-Packard also sent me a catalog, but by this time, I
was a college student. I was most interested in their frequency counters
and time/frequency stuff. I eventually acquired (surplus again) the famous
5245L and later a 5248M. Both still work. Also a 107BR quartz standard
which also still works. More recently, a 105A quartz standard. I ran this
thing against WWVB with a Fluke VLF receiver and the 105A achieves 1 part
in 1E11. The frequency and time stuff is for fun. The Tek connection?
Checking the sweep frequency against the standard output.

The Tektronix parts folks were also very kind. I even had an account with
them, and though they offered to let me buy parts on credit (at least up to
a certain amount - I could not buy a replacement CRT on credit). It was
great for manuals that were still in print, knobs, etc. I was lucky and the
scopes I used and maintained did not need any custom parts. I did replace a
couple of tubes in the 500s, though. I did pay the invoices quickly when i
got them.

I had directed others to Tektronix when they were looking for video test
equipment. When we needed high-resolution, high performance (spot size
uniformity across the CRT face, very low distortion) we bought Tektronix
monitors for the lab (medical imaging). Tektronix being nice to a very
young electronics enthusiast paid off for them.

Steve H

On Wed, May 27, 2020 at 10:06 AM Chuck Harris <cfharris@...> wrote:

Hi Roy,

I guess the first thing is that tektronix made these scopes to
be reparable by their customers. That is why they made available
such detailed manuals for their scopes.

I am pretty sure they figured that if the customer was not
up to the challenge, the high price of replacing the scope if
they failed, would discourage unqualified repairs. And, for those
who would not be discouraged, they had a school for turning
unqualified repairmen into repairmen.

A major point that everyone should realize is these scopes are
scrap in as far as the commercial market goes. That is why they
are in the hands of novice owners. If the novice owner botches
the repair, it just moves a little closer to the scrap bin.

Every major collector's field has this debate at some point.

I have heard the museum guys argue the point successfully in front
of legislatures that metal detectorists should be jailed for
disturbing as yet unknown archeological digs with their explorations.

I have heard warbird enthusiasts demand that warbird owners should be
jailed for flying (and occasionally crashing) the airplanes they saved
from oblivion, and own.

I have heard coin collectors cry when some amateur polishes some
marginally significant coin, ruining its value...

And, I have heard a very, very, few guys like you worry about the
damage a novice may do to a scope that you don't even want...

I guess we have reached the big time!

As for paying $100 for a repair... I repair scopes cheaply, and even
I won't work on a 475 for that little.

-Chuck Harris



Roy Thistle wrote:
Hi all TekScopers:
Reading through a long thread, recently posted, caused me to wonder..
just what are TekScopers accomplishing with threads like this... and why
are we encouraging someone who is "... new to electronics..." to dig into a
475?... one of the most complex, and compact, analog instruments ever
designed.
I suppose.. in consideration... Michael discouraged the use of a Mr.
Carlson super Weller-kluge special, on the 475's pcb(s)... but, ya know...
somewhere the thread... the 475 owner hints he paid 20.00 for 475?, and
he's also got a nonworking? PM3218 too.
So why didn't someone just recommend/... right off the bat... to take
the 475 to someone who knows what they are doing... drop another 100.00 on
it... and then he'd have one of the best scopes ever made.
Or alternatively... and better... just start in on the PM3218...itself a
very fine instrument, with a double insulated power supply... and way
overkill, for a beginner.
Look, I'm not unsympathetic... it's just that...too often.. after
parting with some scarce cash... or finding some Tek picked apart in a
basement somewhere, where its been languishing for a generation...I've
witnessed the havoc wreaked by someone trying to "fix" them.
If you want to call me a dumb ass... for thinking this way... well
fine... just PM me to do it. I can't promise I'll reply to that... but,
I'll read your message.
Best regards and wishes.
Roy
Re: 475 questions

 

Bruce,

The square pad is TEKs way of designating the positive side of any polarized device. So Yes, square pad is + side of the Capacitor. This also applies to diodes as well. Sometimes Tek will use the square pad to designate the number one pin of an IC, however, this is not universally true. The number one pin can also be designated by a small round dot on the PC board, adjacent to the pad. The number one pad is sometimes not identified in any manner. My experience is working many of these 4xx Series as well as other contemporary Tektronix instruments. This holds true on almost all the instruments that I have personally repaired. I do not always depend on the color codes on these caps, I tend to rely on the values stated in the schematics and in the parts list. One thing that I try to do is take a picture of the area of the board where I am working, BEFORE I make any changes and I try to document exactly these sort of markings for later reference.
--
Michael Lynch
Dardanelle, AR
Re: 475 questions

 

Bruce, the + sign is unambiguous, that lead is definitely the postive lead.? The 'bent knee' lead may be the + lead but I am not aware of that as a convention so trust the markings.? Likewise the square solder pad may be a Tek convention (can other readers comment?) but I am not aware of it so I wouldn't rely on it.? Not having access to a 475 I can't get a good look at the A7 board and the image of the PCB layout, Fig 7-16 in the manual is very grainy and I can't see the shape of these pads.? The best way to confirm which way around these tantalums should be is by looking at the pics you took of the board before you removed them!? Yes I forget to do that too, but it's very helpful in these circumstances.? I did refer to the pic of C1091 you posted but the focus is a bit off where it's needed.? I *think* the + is on the left as that looks like the 'bent knee' lead but I'm not certain.

The next best way is to identify nearby components and find which connects to which, and the schematic shows those two ferrite bead inductors L1091 and L1093 and they tell the story.? Note that supply rail to L1091 and C1091 is negative and the other L and C are on a postive supply rail so the capacitor polarity will reflect that.

As for the colourful tantalum on the A9 board, I worked out the colour code as you did and I can't explain the difference with the parts list.? That could be a wild goose chase all of its own so unless you have reason so suspect its motives, I think the sleeping dog principle applies.

Graham

On 28/05/2020 9:43 am, ciclista41 via groups.io wrote:
Hi Graham,

I try to treat people that way, too. After my brief adventure with C1091 and C1093, I'm doing the same with tantalum caps in this scope.

The leads on this tantalum are not symmetrical to the body. If you look at them as legs on a body, one seems to have a knee bent out to the side rather than dropping straight to the floor. There is a + sign printed closer to that leg. I'm guessing that's the positive lead. The through holes they came out of have a square trace pad and a round trace pad. I'm guessing these are to guide polarity. I think the positive leg went to the square, while the negative went to the round, but I'm not absolutely sure of that. Confirmation? Is this a standardized thing?

At /g/TekScopes/photo/247625/0?p=Created,,,20,2,0,0, you'll see an even more colorful one I found on my A9 board. Who knew these scopes were wearing jewelry when no one was looking?

According to this chart: , that's a Red=2, Violet=7, Grey=.01 multiplier, Green = 16V.
So that's .27μF, right? But the manual says this is a 196D275X9050JA1 or a 290-0573-00. The latter is listed in the Tektronix Common Parts Catalog as 2.7μF, 50V. What am I not getting?

Bruce

On Wed, May 27, 2020 at 07:40 AM, VK1GVC wrote:

Bruce, I treat tantalums like I treat people - assume they have good
intentions unless I learn otherwise.? If you remove lots of them without
reasonable suspicion then you'll probably do more damage than good as
Eric has warned.? As tantalums usually fail to a short circuit, a
failed/shorted tantalum will pull down the voltage at that point to
close to zero and this will/should be straighforward to find - later.
At this stage, if I haven't missed any key points, you've found 2
sick/dead capacitors in the +50V supply which MAY be the cause of all
the wrong voltages you've measured in the low voltage power supply
section.? So replace those caps first, then adjust all of the LV power
supply to meet calibrations specs and see what happens.? You might have
a working scope if luck is very much with you, or you might be one step
on a long journey towards that goal.

And when you replace the tantalum which lost a leg, make sure you
install the new one with the right polarity.? Tantalums don't like
reverse voltage and they can get hot, emit smoke and explode.? I've seen
it happen when a workmate powered up some newly assembled eqpt for the
first time and heard a hissing sound so he bent down for a better look.
A cylindrical metal tube type tantalum then exploded and flew off the
PCB, burning itself onto the side of his neck. Very painful ... and the
language was terrible.? And very lucky he didn't get hit in an eye.

BTW here's a different type of tantalum which I don't think has been
mentioned yet - see the colourful little blob in the lower left of the
picture at this link:
/g/TekScopes/photo/12901/22?p=Name,,475,20,1,0,0

It has a black top, brown middle and green bottom ... the colours are a
derivative of the resistor colour code and I think there's a spot on one
side too.? Much better dressed than a plain boring tantalum!

Graham

On 27/05/2020 3:28 pm, ciclista41 via groups.io wrote:
Graham,

Well, my scope is peppered with the kind in the photo. Maybe they
re-spec'ed the caps later in production, or maybe the US Army bought enough in
their contract with Tek that they were able to spec what they wanted. Mine is
from November of 1982, if the date code on the AC power cord box inside the
case just above the transformer is original.
I went ahead and pulled the two tantalums out of the circuit to measure
them. I broke a lead off the first one, pulling too hard. Because I only
have access from the top of this A7 board unless I remove it, which I don't
want to do, my solder sucker wasn't able to slide over the clipped end of the
leads, and I had to just use a sharp tip on my iron. Did much better on the
second one, which came out easily by that second method. I then used the
sucker to remove the remaining solder from the holes in the board for when I
replace the broken one.
Yes, you were right to question my belief that they were bad. Out of
circuit, they both tested well within the green on my ESR tester. So much for
being able to reliably test capacitors in circuit with that thing. They
weren't even close to being in spec when tested with it in circuit. I was
thinking that these dipped tantalums were generally bad in boards this old
based on numerous threads in this forum and others saying how often these were
bad. Some said they routinely replace them all when they see them in a scope
of this era. I have tested dozens on this board and only found about a handful
that this tester considered bad. So, considering that these two were among
the worst that I tested in circuit, I decided to pull them, as they'd be less
easily accessible later when the A8 board is back in place.
So this makes me question whether the tantalums in this board are among the
infamous ones. I hope not, obviously. Your statement that my photo showed
what looked like a very '80's tantalum made me think maybe the infamous ones
are some earlier 60's or 70's version. How can I know, other than pulling
them all? At this point, I don't see the point of pulling any of them unless
they show up as faulty later, when there is a trace on the scope and I can run
it through its paces and make sure it's working as it should.
Speaking of working as it should, Tektronics calls for several specialized
calibration tools in the manual. If the scope is running well, with no
serious issues other than calibration, can it be calibrated without resorting
to the purchase of such tools? I briefly noted some shops wanting a couple of
hundred dollars to calibrate a scope. Definitely don't want to do that! If I
thought I had to have someone else calibrate it, I probably wouldn't have
taken on the project and just invested in a new digital scope.
Bruce

On Tue, May 26, 2020 at 09:09 PM, VK1GVC wrote:

Bruce, the link to the pics on TekScopes worked for me and that
capacitor looks very 1980's tantalum as Michael confirmed in a later 475
manual and the Tek Common Parts manual.? Ceramics of that era were
commonly flat circular disks, very different from what you have.

Roger re testing in place - very problematic.? Best to remove them to
eliminate any ambiguity and as you have reported success in desoldering
then that's the best option while you have access.? BTW I'm curious to
know why you *believe* that they are faulty - mere suspicion based on
type and age, or something else?

You quoted your post of 22 May to Harvey a few minutes ago in which you
sought advice about what can and cannot be substituted when replacing
1982 components in 2020.? Has that qn been answered to your satisfaction
or is it still a live issue?? The short answer is: it depends.? The long
answer really has to address a specific component in a specific
application.? But the laws of physics haven't changed a lot in the last
40 years so there is almost certainly something out there which can be
bought/found/made/adapted or cajoled to do the job.? If you need a 1amp
400V rectifier diode then a IN4004 of the 70's or 80's is just the same
as one from the factory today.? If you need a very specific high-spec
module made for or by Tek for a very challenging application 40 years
ago and now out of production ... oh dear, you've got a problem.
Fortunately we now have TekScopes, some wikis, eBay and of course the WWW.

Graham

On 27/05/2020 1:24 pm, ciclista41 via groups.io wrote:
Hi Graham,

I posted a photo of the C1091 tantalum, along with the plaque stuck to the
back of my scope here:
/g/TekScopes/album?id=247625&p=Created,,,20,2,0,0

Bruce


--
This email has been checked for viruses by Avast antivirus software.
Re: Tek 4041 GPIB Controller

 

I found two resistors next to the keyboard header on the CPU board. One was about 130 ohms to Ground, the other was about 120 ohms to +5V.
The other end of both resistors next to the keyboard header was connected on the PCB to the TX pin from the keyboard.

I unsoldered the end of the 130 ohm and 120 ohm resistors on the opposite side from the keyboard header.

I inserted a 1K ohm resistor into the hole where the 120 ohm resistor was connected to +5V and connected the other end of that resistor to the end of the 120 ohm resistor.

I didn't have to remove the CPU board for this operation.

This allowed my Parallax USB to TTL serial to work. This converter has female pins and I used Arduino breadboard jumpers to connect the serial interface to the LEMO pins.

From the front panel, the top left LEMO female socket is Ground - and was connected to the Parallax Vss pin.
The bottom left male pin on the LEMO is the TX pin from the keyboard and I connected it to the Parallax TX pin.

I could now type on the PC Realterm application (4800 8N2) and see the output on the red LEDs on the front panel.

I then typed two commands - from maddisassembler in 2016 "RE: 4041 basic program for redirection", but left off the line numbers and typed in immediate mode:

SET DRIVER "COMM0(BAU=9600,FLA=BID):"
SET CONSOLE "COMM0:"

I got an error message on the second command. The operators manual shows "SET CONSOLE "COMM:", so I typed that and that text stayed on the LED display - but my serial console was then enabled.

I guess COMM0 is needed if you have the second COMM port option. The 4041 I was using has only one COMM port.

I uploaded a photo of my simple mod. I left the two original resistors if I wanted to restore to original later.

/g/TekScopes/photo/247590/0?p=Created,,,20,2,0,0

Monty
40941 - 40960 of 208346