-----Mensaje original----- De: [email protected] [mailto: [email protected]] En nombre de Chuck Harris Enviado el: domingo, 29 de abril de 2018 6:19 Para: [email protected]Asunto: Re: [TekScopes] Nuvistors The tunnel diode indeed does have the V/I curve shown in the books, but only if the load resistance is zero, or very near zero. The slope of that load resistance's load line has to be so steep that it only touches the negative resistance curve at a single point, as I recall. I think of that as swamping out the diode, or forcing it. The magically weird part of TD's is almost impossible to miss. If you pick a load resistor that is high enough that its load line intersects the TD's characteristic curve at only two points, it will demonstrate something to you that is seemingly impossible. A two point intersection puts the load line intersection very near the first current peak, and somewhere on the second current rise. As you raise the voltage across the series diode and resistor, the current will rise up from zero along the characteristic curve of the TD, until it reaches the point where the load line touches the curve near the peak, and it will suddenly snap over to the other intersection point of the load line. If you continue raising the voltage, the current will then follow the TD curve up to infinity, or the diode burns out. Because the theoretical maximum switching frequency of a TD is something greater than a million megacycles, this switch will be too fast to see. Hard to describe, pictures would make it easier, but I am not up for drawing, scanning, and posting the pictures right now. You can easily find the info elsewhere with a search. If you have your curve tracer set to any resistance load that is higher than the just about zero, you will see this switching phenomenon in your curve, which is what I was describing earlier. We were talking about TD switches, after all. -Chuck Harris OBTW, I think my Dad gave me that GE manual back in the mid 1960's. By gave, I mean that it got put on a shelf that I could reach without asking... so I did... A lot. Ed Breya via Groups.Io wrote:
See this 1961 GE TD manual:
elDiodeManual.pdf
The curve tracer circuit begins on page 66.
You need very low resistance and parasitic L and C to get the true LF/DC-version of what's going on. On a regular curve tracer, even with fairly low series R, the blank part is likely where the whole thing is oscillating while it's biased in the negative R zone, so the CT can't see it. With the right resistance levels and conditions, the TD can be biased at any point on its I-V curve - even right in the middle. The circuits described even need different heads specific to the TD current range to get proper viewing - it can be tricky, but it's doable.
Ed
|
The tunnel diode indeed does have the V/I curve shown
in the books, but only if the load resistance is
zero, or very near zero. The slope of that load
resistance's load line has to be so steep that it
only touches the negative resistance curve at a
single point, as I recall.
I think of that as swamping out the diode, or forcing it.
The magically weird part of TD's is almost impossible
to miss. If you pick a load resistor that is high
enough that its load line intersects the TD's characteristic
curve at only two points, it will demonstrate something
to you that is seemingly impossible.
A two point intersection puts the load line intersection
very near the first current peak, and somewhere on
the second current rise.
As you raise the voltage across the series diode and
resistor, the current will rise up from zero along the
characteristic curve of the TD, until it reaches
the point where the load line touches the curve near
the peak, and it will suddenly snap over to the other
intersection point of the load line.
If you continue raising the voltage, the current will
then follow the TD curve up to infinity, or the diode
burns out.
Because the theoretical maximum switching frequency
of a TD is something greater than a million megacycles,
this switch will be too fast to see.
Hard to describe, pictures would make it easier, but
I am not up for drawing, scanning, and posting the
pictures right now. You can easily find the info
elsewhere with a search.
If you have your curve tracer set to any resistance
load that is higher than the just about zero, you
will see this switching phenomenon in your curve,
which is what I was describing earlier.
We were talking about TD switches, after all.
-Chuck Harris
OBTW, I think my Dad gave me that GE manual back in
the mid 1960's. By gave, I mean that it got put on
a shelf that I could reach without asking... so I did...
A lot.
Ed Breya via Groups.Io wrote:
toggle quoted message
Show quoted text
See this 1961 GE TD manual:
The curve tracer circuit begins on page 66.
You need very low resistance and parasitic L and C to get the true LF/DC-version of what's going on. On a regular curve tracer, even with fairly low series R, the blank part is likely where the whole thing is oscillating while it's biased in the negative R zone, so the CT can't see it. With the right resistance levels and conditions, the TD can be biased at any point on its I-V curve - even right in the middle. The circuits described even need different heads specific to the TD current range to get proper viewing - it can be tricky, but it's doable.
Ed
|
Re: Hello from new old member
Hi GeorgeP,
I'm over in Toronto, Ont., I don't mind driving over for big items.
I only saw 5 items on Ebay, can you post a list we could look at?
Thanks,
Peter
toggle quoted message
Show quoted text
On Friday, April 27, 2018, 5:36:49 PM EDT, GeorgeP <george@...> wrote:
Hello from Lions Head Ontario Canada.
I was on the yahoo board much more often five ten years ago when I was near Georgetown ON.
I got a lot of help and ideas (Thank You!) and was also able to help out a few times.
I am new at this TekScopes Home!
BTW I am downsizing. I have way too much stuff!
George Plhak
ffwdm and george.plhak on EBay
|
Re: 700 Pages of Tekscope, back to 1959, searchable, PDF download: https://ia800209.us.archive.org/21/items/tektronix_Service_Scope_Oct_1959_-_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
Hi Dennis, On Sat, 28 Apr 2018 18:59:06 -0700 "Dennis Tillman W7PF" <dennis@...> wrote: That's not all...
there is much more Tektronix manuals, catalogs, app notes, etc on
this site. I've used archive.org a lot - but wasn't aware of using the "search metadata" tool to create a compilation of an subject such as "tektronix". Good stuff... Lyle
Dennis Tillman W7PF
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Lyle Bickley
Sent: Saturday, April 28, 2018 6:46 PM
To: HankC, Boston, WA1HOS via Groups.Io
<hankc918@...> Cc: [email protected]
Subject: Re: [TekScopes] 700 Pages of Tekscope, back to 1959,
searchable, PDF download:
_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
On Sun, 29 Apr 2018 01:36:22 +0000 (UTC) "HankC, Boston, WA1HOS via
Groups.Io" <hankc918@...>
wrote:
HankC, Boston WA1HOS Thank you, Hank!!!
Lyle
--
Lyle Bickley
AF6WS '73
"Black holes are where God is dividing by zero"
-- Lyle Bickley AF6WS '73 "Black holes are where God is dividing by zero"
|
Re: 700 Pages of Tekscope, back to 1959, searchable, PDF download: https://ia800209.us.archive.org/21/items/tektronix_Service_Scope_Oct_1959_-_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
That's not all...
there is much more Tektronix manuals, catalogs, app notes, etc on this site.
Dennis Tillman W7PF
toggle quoted message
Show quoted text
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Lyle
Bickley
Sent: Saturday, April 28, 2018 6:46 PM
To: HankC, Boston, WA1HOS via Groups.Io <hankc918@...>
Cc: [email protected]
Subject: Re: [TekScopes] 700 Pages of Tekscope, back to 1959, searchable,
PDF download:
_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
On Sun, 29 Apr 2018 01:36:22 +0000 (UTC) "HankC, Boston, WA1HOS via
Groups.Io" <hankc918@...>
wrote:
HankC, Boston WA1HOS Thank you, Hank!!!
Lyle
--
Lyle Bickley
AF6WS '73
"Black holes are where God is dividing by zero"
-- Dennis Tillman W7PF TekScopes Moderator
|
Re: 700 Pages of Tekscope, back to 1959, searchable, PDF download: https://ia800209.us.archive.org/21/items/tektronix_Service_Scope_Oct_1959_-_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
On Sun, 29 Apr 2018 01:36:22 +0000 (UTC) "HankC, Boston, WA1HOS via Groups.Io" <hankc918@...> wrote: ?HankC, Boston WA1HOS Thank you, Hank!!! Lyle -- Lyle Bickley AF6WS '73 "Black holes are where God is dividing by zero"
|
Re: Help with 24x5B processor board A5 and option 5 timer trigger
The original mask is unscathed.? But I am surprised that Tek did not cover the guard traces with mask.? They are just traces after all and covering them with mask would simplify repairs like this.? I understand the need for a good liquid flux, preferably no-clean which I clean after anyway.? But the pitch on these pins is so tight that, in most cases, any trace passing between would be masked.? These are not.? I wonder why. ?
I don't usually make a big deal of soldering a simple part to a board, done it many times.? But I have never cooked a part with my heat wand before and it has me a bit skittish.? So, I am being extra careful (some might say obsessed) so I know the part isn't damaged.? Then if the MUX doesn't work I can confidently look elsewhere for the problem.
Thanks again for your advice and help.
toggle quoted message
Show quoted text
On ?Saturday?, ?April? ?28?, ?2018? ?07?:?35?:?35? ?PM? ?CDT, Chuck Harris <cfharris@...> wrote: My question would have to be: did you damage that solder mask the last time you worked on the MUX? If not, it should be fine the way it is. It is the flux that allows the solder to pull back into a blob.? Without a good flux, it forms oxide stringers that allow bridges.? Good flux, and everything works out nicely. I keep the board under preheat the entire time I am working on the topside.? When I am done, I just turn it off, and let the board cool down naturally.? I find that there are fewer stress problems that way. Let us know how you like working with the preheater.? You should see a remarkable difference. -Chuck Harris machineguy59 via Groups.Io wrote: ? I plan to replace the MUX (U2530) this weekend and wonder if I can put solder mask on the guard traces between signal pins?? I would use Circuit Works CW2500 epoxy which is good to 350 C.? I cant think of any downside and it would help avoid solder shorts.? The guard traces are very close to the signal pins and shorts mean rework with solder braid.? 14 pins at this pitch are sure to get one that needs touch up.?
I haven't decided yet whether I will do hand soldering or hot air.? I purchased a griddle at Walmart for $18.00 to act as a preheater and calibrated it with my IR temperature meter.? Its easy to hold the temperature around 170 C.? I will use a hand held fan to cool the board after soldering and before lifting it off the griddle so I don't temperature shock the board.? But I may loose my nerve and just hand solder the new part.? Either way, I think solder mask over the guard traces would help keep the solder from overflowing.?
|
700 Pages of Tekscope, back to 1959, searchable, PDF download: https://ia800209.us.archive.org/21/items/tektronix_Service_Scope_Oct_1959_-_Sep_1971/Service_Scope_Oct_1959_-_Sep_1971.pdf
|
See this 1961 GE TD manual:
The curve tracer circuit begins on page 66.
You need very low resistance and parasitic L and C to get the true LF/DC-version of what's going on. On a regular curve tracer, even with fairly low series R, the blank part is likely where the whole thing is oscillating while it's biased in the negative R zone, so the CT can't see it. With the right resistance levels and conditions, the TD can be biased at any point on its I-V curve - even right in the middle. The circuits described even need different heads specific to the TD current range to get proper viewing - it can be tricky, but it's doable.
Ed
|
Re: 453 cleaned up and running.
Wow, what a nice clean up job you did... makes mine look like a mess, by comparison!? Congratulations.
Phil
toggle quoted message
Show quoted text
On 4/28/2018 4:51 PM, lop pol via Groups.Io wrote: Here it is cleaned up and running.
|
Re: Help with 24x5B processor board A5 and option 5 timer trigger
My question would have to be: did you damage that solder
mask the last time you worked on the MUX?
If not, it should be fine the way it is.
It is the flux that allows the solder to pull back into
a blob. Without a good flux, it forms oxide stringers
that allow bridges. Good flux, and everything works
out nicely.
I keep the board under preheat the entire time I am
working on the topside. When I am done, I just turn it
off, and let the board cool down naturally. I find that
there are fewer stress problems that way.
Let us know how you like working with the preheater. You
should see a remarkable difference.
-Chuck Harris
machineguy59 via Groups.Io wrote:
toggle quoted message
Show quoted text
I plan to replace the MUX (U2530) this weekend and wonder if I can put solder mask on the guard traces between signal pins? I would use Circuit Works CW2500 epoxy which is good to 350 C. I cant think of any downside and it would help avoid solder shorts. The guard traces are very close to the signal pins and shorts mean rework with solder braid. 14 pins at this pitch are sure to get one that needs touch up.
I haven't decided yet whether I will do hand soldering or hot air. I purchased a griddle at Walmart for $18.00 to act as a preheater and calibrated it with my IR temperature meter. Its easy to hold the temperature around 170 C. I will use a hand held fan to cool the board after soldering and before lifting it off the griddle so I don't temperature shock the board. But I may loose my nerve and just hand solder the new part. Either way, I think solder mask over the guard traces would help keep the solder from overflowing.
|
Hi Ed,
I know through artifice that you can create plots
of a tunnel diode. A 576 will do it directly, but
it does not match the actual operation of the part,
When the TD gets to the threshold current, it instantly
drops to the lower threshold point. It doesn't wander
lackadaisically down as the curve shows.
The curve shows as it does because it is so totally
swamped by the capacitance of the analyzer that it
smears a trace from the last point where the V/I was
to where it has switched to.
-Chuck Harris
Ed Breya via Groups.Io wrote:
toggle quoted message
Show quoted text
Regarding the tunnel diode branch from this thread - it is indeed possible to see the complete I-V curve of a tunnel diode in low frequency or DC conditions. Normal curve tracers can't do it because their series R is too high, so it appears discontinuous. Specially made, very low resistance test fixtures can suppress the instability caused by the TD's negative R, allowing display of the actual I-V - even that magical negative R region.
You can find such a test circuit in either (or maybe both - I forget) the GE or RCA TD manuals from the 1960s. The circuit displays the I-V on a scope, just like a curve tracer, but it's dedicated to only this function. I had once thought about building one of these, for curiosity, but for general go-no-go testing of TDs, it's not really necessary to see that part anyway. You can trust that the TD is doing its thing if you can see the endpoints, on a regular curve tracer, or in-circuit.
Ed
|
At 05:24 PM 4/28/2018, 搁别苍é别 wrote: I believe the replacement is MPF102, pin for pin. less filament of course.
On 2018-04-27 08:46 PM, Dale H. Cook wrote:
Tek replaced the front-end, sweep generator, and trigger generator Nuvistors (all 8393) with FETs in the 453 beginning with serial 20,000.
The Tek parts in the serial 20,000+ 453s were N-channel JFETS, a dual FET, Tek part 151-1011-00 in the front ends, and individual FETs, Tek part 151-1005-00 in the sweep and trigger generators. The former crosses to a dual 2N3822 and the latter to a 2N4303. Both show as "FET Tek Spec" in the manual and were likely selected so the channels would match. Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
|
Re: FG504 and failed Q270 (SPS2927)
From the Tek semiconductor data book, the 151-0438-00 was superseded by
151-0712-00, both of which cross to an MPSH81.
Cheers,
Dave M
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
toggle quoted message
Show quoted text
FG504 and failed Q270 (SPS2927)
From: NigelP
Date: Sat, 28 Apr 2018 11:25:43 CDT My FG504 had suddenly died when I tried to use it yesterday (no output
basically). After a lot of probing around I discovered that Q270 on the A3
Loop board had failed. It's specified as 151-0438-00, a selected SPS2927.
I'm sure this one has come up before but I can't find a spec or
alternative device.... can anyone suggest a suitable device please. I've
put in a BC212L just to prove the fault diagnosis but it would be nice to
get the right part.
|
453 cleaned up and running.
I would like to thank one of the list members (you know who you are). It cleaned up nice. I changed the fan last night and replaced the variable time pot today. Here it is cleaned up and running. /g/TekScopes/photo/37195/12?p=Name,,,20,1,0,0 Next I will paint the case and build a light filter for the CRT. Thanks again!
|
Re: Intermittent no trace / sweep.
"of" = "or"
One of my more common typos.
|
Re: Intermittent no trace / sweep.
"( I mentioned I have a shop manual so why do I get advise to download it ?)"
I knew that.
"BTW I have been using this particular scope professionally for few years"
I did not know that. From what I had to go on you could have been a first time scope owner of someone who worked for Tektronix for 20 years. I try to avoid making assumptions because as the old saying goes...
What I do wonder now is how the controls are set up on that scope. On most, if the selector is set to normal sweep the delay controls have no effect. But then I didn't get to the point of finding out.
Under the circumstances all I could do is start from the beginning.
Glad to hear you got it figured out. "We" have some spare knobs from a 422 and a few 7XXX series plugins if they fit and you have trouble finding something that will. My luck is usually not as good, the plastic usually cracks on me and then it won't grab no matter how much you "tighten" the screw.
|
Yes, the driver in my description is voltage, and
the current changes with voltage. Sorry for the
confusion.
-Chuck Harris
Raymond Domp Frank wrote:
toggle quoted message
Show quoted text
Chuck,
A real curve trace of a tunnel diode would show the trace rising to
the trigger voltage, and then reappearing at the near zero triggered
voltage. It would be discontinuous. There is no there there.
Didn't you mean to say "trigger current" and "triggered current"?
Raymond
|
Re: 500-series fan motor disassembly.
Hi there, Just going again into this problem so trying to bring back to life this thread, hoping that someone with experience on this would like to share a good mechanical tip to disassemble the bushings' press-fit retainers. Thanks in advance, Sebastian. PS: Now, also posting this in Tekscopes2 list. On Sat, March 31, 2018 10:13 pm, Sebastian Garcia wrote: Thank you, Shaun.
OK, press-fit retainers; it seems I was missing the correct
English terms.
I'm missing the recommended mechanical tools and technique to properly
dis-assembly it.
Mounting can probably be performed well with a soft plastic hammer.
Perhaps clean up assembly, check the shaft/bushing fit and go from
there.
If I understand correctly, you are suggesting to avoid dis-assemble it.
From a preliminary inspection, I don't think it's an option in my case.
Search the archive for Stan Griffiths' posts, mentioning good reasons to
completely disassemble it.
Sebastian.
On Sat, March 31, 2018 9:40 pm, Shaun M wrote:
Sebastian,
Yes, I see the issue now. Your motor has cast endbells and press fit
retainers. One issue I have found with press fit assemblies is even
granting you can disassemble them without apparent damage, they often do
not reassemble properly.
Perhaps clean up assembly, check the shaft/bushing fit and go from
there.
Shaun Merrigan
On Sat, March 31, 2018 7:13 pm, Sebastian Garcia wrote: I uploaded some pictures:
/g/TekScopes/album?id=42033
As a reminder for anyone reading this (the posts from the web interface
removed the thread history), I'm looking for advice on removing the metal
end caps/retainers of the bushings assemblies.
Sebastian.
On Sat, March 31, 2018 6:44 pm, Sebastian Garcia wrote:
OK, now I see, in your assembly you have access to the tabs.
I will take a couple of pictures and share them in brief.
Thanks you,
Sebastian.
On Sat, March 31, 2018 6:37 pm, Shaun M wrote:
Sebastian,
As I recall, the tabs which hold the retainer to the endbell were
relatively easy to bend starting with a small flat blade screwdriver
followed by needle nose pliers. I bent them only far enough to remove
the
retainer. You can see in the mages that I did not straighten them out.
Shaun Merrigan On Sat, March 31, 2018 6:09 pm, Sebastian Garcia wrote: Hi Shaun,
Thank you; your pics are helpful, of course.
My motors looks a bit different but it seems the bushings assemblies are
similar.
How did you remove the metal end cap / retainer?
Best regards,
Sebastian.
On Sat, March 31, 2018 5:42 pm, Shaun M wrote:
Sebastian,
I disassembled and rebuilt (new bushings, check shaft diameter and wear,
balance blade assy, etc) the fan motor in my Tek 556 which includes many
images of the motor:
You may find it helpful.
Shaun Merrigan
On Sat, March 31, 2018 4:41 pm, Sebastian Garcia wrote: Hi there,
In this corner, just proceeding to clean some 500-series scopes' fan
motors.
There is very good advice in the list's archives, particularly from Stan
Griffiths.
My question: What is a recommended way to remove the metal end caps of
the bushing assembly?
Of course, will also need advice for a way to later put then again in
place.
Regards,
Sebastian.
|
Replacement of nuvistors with JFET's (specifically, MPF102 JFETs) in the
422 scope vertical amplifiers has been accomplished by "Kurt" and was
documented several years ago in his blog. I believe this is also
described at www.w140.com, under the "422" scope webpage. However, the
plate voltage in the 422 scopes is about +25 volts. The plate voltage
of the nuvistors in the vertical preamps of the 453 scopes (early S/N's)
is about +75 volts, so I suspect this would likely zap a MPF102. There
might be other JFETs that have adequate drain-to-source voltage rating
to serve as replacement for the nuvistors in the 453 (early S/N) scopes.
Mike Dinolfo N4MWP
toggle quoted message
Show quoted text
On 04/28/2018 05:24 PM, 搁别苍é别 wrote: I believe the replacement is MPF102, pin for pin. less filament of course.
搁别苍é别
On 2018-04-27 08:46 PM, Dale H. Cook wrote:
At 06:50 PM 4/27/2018, Jeff Urban wrote:
Now that I think about it I bet some of these triodes could be
replaced with depletion mode N channel FETs. Tek replaced the front-end, sweep generator, and trigger generator
Nuvistors (all 8393) with FETs in the 453 beginning with serial 20,000.
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
|
Lyle Bickley
Dale H. Cook
Jeff Urban
Mike Dinolfo