开云体育

Yup, about 49 years that I recall, when it was at Sunset. It sure gives you time to stew over the ones that got away.
Bob.

I think it's always been like that, even in the good old days. I recall it was only open Saturday mornings way back, with similar limited hours. The store is only a small part of the operation - they have a lot more and bigger stuff to deal with, and the occasional open hours are probably about right to get rid of the small items to individual buyers.

Ed

Fellow Tekkies,

I've gotten curious about the rhyme or reason to the RAMS store's
limited public hours (two Thursdays a month, less than half a day).

Thoughts on this?

Thanks much.

--
---
Bruce Lane, ARS KC7GR

kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)

Hi Vincent,
The EEVblog 2215 post, that you gave us the link to, is excellent!
The little part you need would be quite simple to make (and to improve upon) if one had some accurate dimensions from a 2215 knob, shaft and the original part that is broken.
I have lots of 22xx scopes, but they are all from the more common 22xx family of smaller size scopes which would include the 2215A, which is very different from the 2215.
Also, I do not know anyone who has a 2213 or 2215 near me that I could get the measurements from.
Does anyone around Los Angeles have a a 2213 or 2215 knob and and related parts that I could measure?
tom jobe...

You didn't listen to what I said about the electrolyte.

Isopropyl alcohol does tremendous "corrosion" to a styrofoam
cup, but nothing to a piece of aluminum.

The corrosive, to copper, electrolyte in 105C capacitors makes
a mess out of copper, but does nothing to aluminum and aluminum
oxide. An electrolyte can be corrosive to one material, and
totally benign to another.

Years ago, the electrolyte ate the aluminum oxide dielectric
layer. This is why a capacitor from that era needed to be
reformed periodically if you wanted it to meet its nominal
specifications. Today, capacitor plate material is precision
anodized in bulk form, wound up into a capacitor, and given a
highly electrically conductive electrolyte (low ESR) that does
not corrode the aluminum oxide dielectric deposited during the
anodize process.

You may have heard about the counterfeit electrolyte that
appeared in many electronic devices, notably computers, in
the late 90's. This was a case of an electrolyte being used
that was not as noncorrosive as was necessary.

When you operate a modern electrolytic capacitor on lower than
its nominal voltage rating, it is not harmed, and it does not
change in any way.

Ever wonder why today's capacitors are so much smaller for the
same C x V product than were the capacitors originally installed
in the scopes? The reason is the better processioning of the
aluminum plate material allows far fewer errors in dielectric
thickness, and the greatly improved non corrosive to aluminum
oxide electrolyte allows the manufacturer to use a lower voltage
safety factor than before.

Today's 25V capacitor is yesterdays 50V capacitor.

If the electrolyte was as corrosive as you imagine, my bags of
NOS capacitors would have all eaten away their aluminum oxide
dielectric and all be short circuit. They are not. They are
as good as the day they were made. Electrolytic capacitors from
40-50 years ago would be long gone in similar circumstances.

You are limiting your choices based on imagined problems.

-Chuck Harris

OBTW, Nichicon of 1975 is a far different company from Nichicon
of 2018. Dare we compare Tektronix of 1965 to the Tektronix of
today? Neither company has any of the original founders, nor
their instincts for quality, involved today.



M Yachad wrote:

Chuck

“If you need some evidence to back my assertions, grab any old bag of electrolytic capacitors that have been sitting on the shelf for years, and measure the capacitance. They will all measure at the nominal value... after years of being operated at the extremely low voltage of 0V. “

Not sure if you’re trying to be funny, or if you’re serious.

If you’re serious, I think your comparison is irrelevant. Unless a capacitor is in a working environment, coping with heating and cooling cycles, you cannot compare it to a shelf model, no matter what voltage. And statistically, throwing a single bag of old undocumented caps into the ring here, is irrelevant.

“I have just such a bag of nichicons from a project where I overbought the caps. This was back in the 1970's. They all still read 2200uf +/- 10%.”

In the best case, it just goes to prove that Nichicon is still the right choice, today.

...

Chuck

“If you need some evidence to back my assertions, grab any old bag of electrolytic capacitors that have been sitting on the shelf for years, and measure the capacitance. They will all measure at the nominal value... after years of being operated at the extremely low voltage of 0V. “

Not sure if you’re trying to be funny, or if you’re serious.

If you’re serious, I think your comparison is irrelevant. Unless a capacitor is in a working environment, coping with heating and cooling cycles, you cannot compare it to a shelf model, no matter what voltage. And statistically, throwing a single bag of old undocumented caps into the ring here, is irrelevant.

“I have just such a bag of nichicons from a project where I overbought the caps. This was back in the 1970's. They all still read 2200uf +/- 10%.”

In the best case, it just goes to prove that Nichicon is still the right choice, today.

“But, alas, what you say is not true. It once was, back when electrolytic capacitors used rather caustic electrolytes that ate away the aluminum oxide dielectric layer, but that hasn't been the case for about 30 years.”

On the contrary, the low-ESR capacitors of today DO contain corrosive electrolyte.
Do I need to expound on the A5’s damage?

Read up on Chemicon’s recent hard lessons on their KYx KZx and LXx series, with the problems, and subsequent requirement to reformulate the highly corrosive electrolyte.

We only get to know about these problems, LONG AFTER the caps have been installed in the customer’s machine, and he has paid for them.
So why not anticipate the problem, and plan for it?

Therefore, there is enough empirical evidence to support the postulation that the issue STILL exists today.
And I simply do NOT see this as a problem.
We can choose to ignore it, or we can choose to plan our BoM, with the knowledge that a poor choice may bite us in the future.
My way to deal with this exact issue, is to suit the capacitor voltage rating to the actual circuit voltage.
Is that such a difficult decision to make?
To me, it’s simply preempting the possible problems which corrosive electrolytes cause.

It’s a free world.
I choose the path of caution and reliability – I have customers to answer to, and my hard-won reputation to uphold.

A man who’s rebuilding his own scope can throw whatever he wants in there – the only one he needs to answer to, is himself. And in that case, to him, this discussion is irrelevant.

“Just like it was fine when you specified 330uf 50V caps to replace both the 250uf 20V and the 180uf 40V caps in the power supply.”

You’re right – in my PDF, I did say that. I did not pay sufficient attention during my proofreading to differentiate. However, after that PDF was published, there was a lot of positive feedback on this forum, pointing out the errors and suggesting the changes which should be made. All of those changes are included in my ebay repair kit, which has sold nearly 200 units, the vast majority of them not on ebay.

“This isn't audio gear where you have to worry about how the end user might "feel" about your choice. You can use valid technical reasons.”

I’ve been around much too long to give much thrift to what people “feel” about my conservative way of life, much less to audiophools who chase after every new bottle of snake oil. My principle is “First reliability, then sound”. Why? If the machine doesn’t work, then what worth are all the salesman’s promises on the superior sound which it is supposed to it deliver?

G-d bless you all for your input – it’s what keeps this forum alive and each of us learning more as we go along.

Menahem

On Thu, Jun 14, 2018 at 11:42 pm, Dennis Tillman W7PF wrote:

I have absolutely no idea how you tell when either of the two output barrels
are touching the substrate. The only way I think Tek did it was by applying
strobe signals and monitoring the output on the center conductor of the
barrels. As I turned them I kept hoping for some change in resistance
between the center conductor of the barrel and the 5 pins that go into the
cavity. I never got a reading of any kind. In the end I failed to get any
output at all from the head when I was done. It was dead.

Dennis,
This from a Maintenance Note from June 74:
//S-6 SAMPLING HEAD INTERMITTENT OUTPUT
In the past the S-6 Sampling Head has had an Intermittent problem in the Hybrid Bridge Circuit.
The center conductor of the 3mm connector on the front panel connects directly to the bridge sub-strate
via a mechanical spring loaded plunger. The Intermittent output Is caused by the plunger. Norm Farmer of
the Rockvllle Service Center has suggested a field fix which entails cleaning the plunger. When you re-Install
the spring and plunger make sure the plunger is free enough not to bind up when pushed all the way Inside
the center connector, yet not so free that it will fall out when you turn the connector upside down. This
practice insures that the center connector makes good contact with the plunger. The front 3mm connector
will be the only one you probably will have to be concerned about. You will need a wrench to remove the
3mm connector. You can do this by increasing the width slightly of a 3/16th open-ended wrench
The 3mm connector spring and plunger are not shown In the S-6 manual. The part number for the spring
is 214-1072-00, and the plunger Is PN 131-0632-00.//

/H?kan

The input (loop thru) signals J10 and J12 are 10k from another pin, "O".
The output signals at 16k and a diode drop away from another pin ("J" ->-
J15 or J16 ->- "M"). I feel like this should be measurable with an ohm
meter to see when you're making good contact, but I'm not going to find out
the hard way that it doesn't work that way.

All the manual says is "The assembly female 3 mm coaxial connectors may be
replaced by using a small wrench on the flat portion of the connector to
remove and replace a connector from the assembly." (Page 5-1, second to
last paragraph)

Dave Casey

On Fri, Jun 15, 2018 at 1:42 AM, Dennis Tillman W7PF <dennis@...>
wrote:

Inside the S6 Sampling Head there are 3 PC boards. One connects to the
socket inside the 7S12, and nothing else. One is the strobe board, and the
third is the preamp board. They are interconnected in a 3D stack using long
pins. But that is not what my question is about.



At the heart of the S6 is the sampling bridge. This diode bridge is
contained on an extremely thin ceramic substrate inside a very substantial
steel clamshell "cavity". Four SMA barrels and 5 pins enter this "cavity".
I
was troubleshooting one of my S6 heads that had a lot of unusual noise.
This
was not sampling noise which would look like a fat cloud of dots instead of
a thin cloud of dots, Instead the sampling was actually very tight but the
trace was jumping up and down randomly as if there was low frequency
"Popcorn" noise affecting it.



After a few hours of troubleshooting by replacing all three boards of the
noisy head with boards from a good head (and vice versa) I knew the problem
was inside the cavity. I thought there might be a loose bond wire or debris
on the substrate that was slightly conductive so I opened up the cavity to
take a look. I found nothing which might be causing the noise.



But when it came time to put the cavity back together I discovered
something
I have never encountered before. Here is where some mechanical genius at
Tek
had to come up with a solution to a an impossible packaging problem. The
barrels cannot be soldered to the substrate since they will be torqued
during the assembly of the sampling head and this would break any
connection
to the delicate ceramic substrate. They have to be free to turn a bit.



At first glance the SMA barrels look like typical Female SMA to Female SMA
Adapters. But on closer inspection one end has a tiny protruding "male"
pin.
The "male end must be screwed into the cavity after it the top and bottom
halves of the cavity have been screwed together. So there is no way to see
what is going on inside the cavity as you screw it in. Somehow (I haven't
got a clue how) you must stop just as the male tip touches the ceramic
substrate and makes contact with it. If you go any further you can damage
the ceramic substrate.



Since both of the barrels coming out to the front of the sampling head are
connected together (the S6 is a loop thru TDR head) you can carefully turn
the barrels until you get continuity from center pin to center pin of each
barrel since the loop thru connection is made on the substrate.



I have absolutely no idea how you tell when either of the two output
barrels
are touching the substrate. The only way I think Tek did it was by applying
strobe signals and monitoring the output on the center conductor of the
barrels. As I turned them I kept hoping for some change in resistance
between the center conductor of the barrel and the 5 pins that go into the
cavity. I never got a reading of any kind. In the end I failed to get any
output at all from the head when I was done. It was dead.



It did seem to eliminate the noise but it eliminated everything else as
well
:(



Does anyone know how Tek did it?



Dennis Tillman W7PF

For my fading problem I think I have narrowed things down to electrolytic (or is it wet tantalum?) caps, C4327 5uF 150V, and C4006 4.7uF 35v (leaked some). C4327 was arcing sometimes when powering on! These seem like bipolar caps, correct? What are suitable replacements? I see someone recommending electrolytic polar caps, is that right?

Ive placed an order with JLCPCB for adapter PCBs and will be recapping the filtering caps on the PSU soon. Once that is done I will get to work on cleaning up the traces.

I have absolutely no idea how you tell when either of the two output barrels are touching the
substrate. The only way I think Tek did it was by applying strobe signals and monitoring the

output on

the center conductor of the barrels. As I turned them I kept hoping for some change in resistance
between the center conductor of the barrel and the 5 pins that go into the cavity. I never got a

reading

of any kind. In the end I failed to get any output at all from the head when I was done. It was

dead.

Dennis Tillman W7PF

How did you check for a change in resistance, Dennis?

Craig

Inside the S6 Sampling Head there are 3 PC boards. One connects to the
socket inside the 7S12, and nothing else. One is the strobe board, and the
third is the preamp board. They are interconnected in a 3D stack using long
pins. But that is not what my question is about.



At the heart of the S6 is the sampling bridge. This diode bridge is
contained on an extremely thin ceramic substrate inside a very substantial
steel clamshell "cavity". Four SMA barrels and 5 pins enter this "cavity". I
was troubleshooting one of my S6 heads that had a lot of unusual noise. This
was not sampling noise which would look like a fat cloud of dots instead of
a thin cloud of dots, Instead the sampling was actually very tight but the
trace was jumping up and down randomly as if there was low frequency
"Popcorn" noise affecting it.



After a few hours of troubleshooting by replacing all three boards of the
noisy head with boards from a good head (and vice versa) I knew the problem
was inside the cavity. I thought there might be a loose bond wire or debris
on the substrate that was slightly conductive so I opened up the cavity to
take a look. I found nothing which might be causing the noise.



But when it came time to put the cavity back together I discovered something
I have never encountered before. Here is where some mechanical genius at Tek
had to come up with a solution to a an impossible packaging problem. The
barrels cannot be soldered to the substrate since they will be torqued
during the assembly of the sampling head and this would break any connection
to the delicate ceramic substrate. They have to be free to turn a bit.



At first glance the SMA barrels look like typical Female SMA to Female SMA
Adapters. But on closer inspection one end has a tiny protruding "male" pin.
The "male end must be screwed into the cavity after it the top and bottom
halves of the cavity have been screwed together. So there is no way to see
what is going on inside the cavity as you screw it in. Somehow (I haven't
got a clue how) you must stop just as the male tip touches the ceramic
substrate and makes contact with it. If you go any further you can damage
the ceramic substrate.



Since both of the barrels coming out to the front of the sampling head are
connected together (the S6 is a loop thru TDR head) you can carefully turn
the barrels until you get continuity from center pin to center pin of each
barrel since the loop thru connection is made on the substrate.



I have absolutely no idea how you tell when either of the two output barrels
are touching the substrate. The only way I think Tek did it was by applying
strobe signals and monitoring the output on the center conductor of the
barrels. As I turned them I kept hoping for some change in resistance
between the center conductor of the barrel and the 5 pins that go into the
cavity. I never got a reading of any kind. In the end I failed to get any
output at all from the head when I was done. It was dead.



It did seem to eliminate the noise but it eliminated everything else as well
:(



Does anyone know how Tek did it?



Dennis Tillman W7PF

$100 for a 067-0587-02 calibration plug in is a steal.

Craig

my scope has the vacuum tube rectifiers - I am pretty sure the CRT is OK because I have gotten it to run for a bit and it makes a fine display. For now, I'm inclined to blame caps - specifically the ones in the grid circuits with the silicon diodes, not the HV ones. I disconnected the grid circuits by removing the diodes, and the HV supply made HV and the current drawn through the oscillator transistor was well under an amp (sorry, I didn't write down the number). There are some orange colored rectangular axial leaded ceramic caps, .015 at 2.5KV. I've ordered some .03 ceramic caps and I just got a bag of .01 ceramic caps, both rated 3KV (so safely more than the original ones). they are quite a bit smaller though - I'm inclined to say that they have newer ceramic with better dielectric but I worry that there is some other parameter that isn't specified that the original caps meet and these don't - I suppose the "easy" thing is to just swap them and try.

I am also thinking that if it is really the HV transformer, a 3KV supply from a Xerox machine is a tiny little module, and 12KV isn't all that big either, so a modern potted replacement might make sense rather than rewinding. but I'll cross that bridge when I come to it.

I saw that pallet; I think there's a 323 in there.

The contact's name is Volker Klocke at oscilloscopemuseum at gmail dot com.
Located in Western MA, I've never visited it.

Wow!? I haven't seen a pallet like that since I bought my two.? I'm SO glad I'm not closer!
-Dave

From: David Berlind <david@...>
To: [email protected]; Dennis Tillman W7PF <dennis@...>
Sent: Thursday, June 14, 2018 7:03 PM
Subject: Re: [TekScopes] FS: Tektronix scopes on craigslist; North of Boston, MA

BTW... just up the road from Shannon is a full pallet of Tektronix stuff.



On June 14, 2018 9:32:45 PM "Dennis Tillman W7PF" <dennis@...> wrote:

Hi Shannon,
I was not aware of this museum until you mentioned it. Where are they
located and who is their contact in the US?
Dennis

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Shannon Hill
Sent: Thursday, June 14, 2018 6:00 PM
To: [email protected]
Subject: Re: [TekScopes] FS: Tektronix scopes on craigslist; North of
Boston, MA

Thanks, decided to donate a 555 and a 536 to oscilloscopemuseum.com .

--
Dennis Tillman W7PF
TekScopes Moderator

BTW... just up the road from Shannon is a full pallet of Tektronix stuff.

Finally got this thing fixed. Looks like someone attempted to repair a bridge rectifier and during the process tore out the through hole plating. I'm going to order some eyelets and a staking tool when I get some money. Anyway here it is.

/g/TekScopes/photo/56393/1?p=Name,,,20,1,0,0


'm working on a 465 pre serial # 250,000. I'm having a hard time locating the schematic for this early scope. If anyone has a link or one they would share that would be awesome. I changed all the LV power caps but there is no HV and the -8V,15V and 5V are all low. Ground to to the -8V TP is 55ohm. Ground to 15V TP is 176ohm and ground to 5V TP is 103ohm. I removed the HV multiplier ground jumper with no difference in any voltages. Pin 8 of U1524 is the correct 28V. Pin 4 of U1554 is 1.5V (supposed to be -8V) and pin 8 is 0V (supposed to be 15V). *Im hoping all these numbers are close because I don't have the correct schematic*

5V TP meter reading is .6V
15V TP meter reading is 1.5V
-8V TP meter reading is +.7

55V TP meter reading is 55v
110V TP meter reading is 109.5

Hi Shannon,
I was not aware of this museum until you mentioned it. Where are they located and who is their contact in the US?
Dennis

Thanks, decided to donate a 555 and a 536 to oscilloscopemuseum.com .