Date   

Re: GPIB Connection to 2340A - Response garbled #photo-notice

 

To increase reference value for posterity, you may consider changing modelno. to 2430A.

Raymond


GPIB Connection to 2340A - Response garbled #photo-notice

Joerg
 

Hi all,
I've been trying to use use GPIB interface on my 2340A and had only limited success so far. I've bought a Prologix GPIB-USB adapter for the task. I can connect to the instrument and send commands that show up on the debug screen - see https://groups.io/g/TekScopes/photo/263696/3241684?p=Created,,,20,2,0,0 - here just asking for the instrument to identify. The response, however, is not intelligible. The settings I've used on the scope are here: https://groups.io/g/TekScopes/photo/263696/3241685?p=Created,,,20,2,0,0

And the python code I've used is

import pyvisa
rm = pyvisa.ResourceManager('@py')
inst = rm.open_resource('ASRL/dev/cu.usbserial-PX4QY88I::INSTR')
inst.baud_rate = 9600
inst.read_termination = '\n'
inst.write_termination = '\n'
inst.timeout = 2500
inst.encoding = 'latin-1'
inst.query("*IDN?")

and which returns 'ÿ\r'

setting the instrument encoding in python to 'ascii' (the default) instead of 'latin-1' results in an error as byte 0 cannot be decoded. I'm working a Mac and would like to keep working in python and the http://www.ke5fx.com/gpib/readme.htm toolkit is Windows only.

Any help is greatly appreciated.


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

I see, so you keep workshop notes, thats cool! I should start doing that too.
For good measure I deoxied (with the Italian version of that :) ) all the switches and gived them a good wiggle but nothing.
Federico


Re: 576 Curve Tracer FET Adapter Differences

Michael W. Lynch
 

Dan,

You are correct! Upon closer examination, what first looked like small rivets were actually shallow headed hex screws. I was able to get it apart. Upon opening the unit, it was then possible to gently push the PC board down and the little ferrule would make connection while you held slight down pressure. So I knew something was amiss. After carefully pulling the PC board, I found that one of those little pins that you were speaking of had been previously broken off and was already completely missing. So there was no connection at one pin. I was able to rig up a suitable repair and make the thing work. Now it operates as it should. THANK YOU for the good advice.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: 576 Curve Tracer FET Adapter Differences

Dan G
 

On Tue, Jun 8, 2021 at 10:00 PM, Michael W. Lynch wrote:

Is there any way to open this adapter? It appears to be sealed and
non-serviceable.
That is odd. Every adapter I've seen (both 013-0098 and 013-0099) has
a set of six 5/64" hex head screws accessible from the bottom of the
adapter. Perhaps Tektronix switched to a snap-in design at some
late stage without changing the part number? If so, I wouldn't hazard
a guess on how to open the enclosure without damage.

If you do manage to open the plastic enclosure, I do have one word
of warning: the PCB inside is probably sitting on a set of six very thin
pins that protrude from the rear ends of the banana plugs. If you need to
remove the PCB, lift it very carefully and evenly upwards, so as to avoid
tilting the PCB and breaking the pins. I find that one end of an IC puller
works well to slowly work around the edges of the PCB as it is
gradually pulled up.

Best of luck,
dan


Re: 576 Curve Tracer FET Adapter Differences

Michael W. Lynch
 

Dan,

Thanks for the quick reply! I did not think to look at the service manual. The curve tracer is working properly as it will test transistors and diodes perfectly on both left and right sides. I have since found that the right side Fixture Drain pin connection is open, so the fault it is in the adapter. Is there any way to open this adapter? It appears to be sealed and non-serviceable. I appreciate you getting back to me as I was having problems making the pieces of the puzzle fit together.

Sincerely,

--
Michael Lynch
Dardanelle, AR


Re: 576 Curve Tracer FET Adapter Differences

Dan G
 

013-0098-02 is the same: only five pins. The emitter sockets on the curve tracer
should be permanently tied together (regardless of the position of the selector
switch), so two emitter pins are not needed on the adapter.

Perhaps there is a wiring fault in your 576 standard test fixture? Or there may
be a wiring fault in your -02 adapter. I have a 577/177, and can confirm that the
emitter sockets are shorted.

I don't have a 576, but the service manual shows the two sockets being shorted
there as well.


dan


576 Curve Tracer FET Adapter Differences

Mlynch001
 

Can anyone explain why the 013-0099-02 FET adapter only has 5 pins on the back while the 013-0099-00 has 6 pins? Looking for instructions and cannot find them. I cannot make the right side of -02 work on my 576 or 577. While -00 connects to all 6 jacks of the tracer; the 02 does not connect the right side of the adapter (S - source) to the right side emitter jack of the curve tracer. Please help my feeble mind understand. What am I missing?

Thanks!
--
Michael Lynch
Dardanelle, AR


Re: Problems with t935a HV supply

Ozan
 

Ozan:

Thank you for your explanation. That seems to make sense.

I did not fully understand how the control loop works until I read your
explanation.
--
Service manual section "II.1" on page 92 has a very good description of the control loop. Since you are seeing ~ -2000V at cathode regulation loop probably is fine.

At a high a level you can use the following analysis to examine the regulation loop:

CR443 cancels Vbe of Q446 to reduce tempco of the loop. Drop across R446 is very small (assume zero), and collector current (therefore base current) of Q446 is very low.

We can assume current through R444A (68.5k) is same as current through R44B+R444D//R468+R444C (total 17.09M) branch.
(Vcathode-Vbe)/17.09M=-(8V+Vd-Vbe)/68.5k
Vd=drop of CR443
Vbe=Vbe of Q446
Assume Vd=Vbe ~= 0.7V
--> Vcathode ~= -1995V (-2000 expected, very close match).

Some of the expected voltages are on the schematic, in particular checking collector of Q454 (-0.45V expected) shows if Q458 is driven harder than normal.

I will check CR465 and CR463 as well as the voltage divider chain R444B and
R444C.
If the voltage at cathode is ~ -2000V voltage divider seems to be fine. Division ratio is (R444C+R444D//R468+R444B)/R444A. Resistor R444A has an important weight too.

As I wrote earlier checking CR465 and CR463 needs high voltage. I haven't seen myself but some of the reported failures in diodes of HV section only showed up at higher voltages.

Ozan


Re: Problems with t935a HV supply

 

Ozan:

Thank you for your explanation. That seems to make sense.

I did not fully understand how the control loop works until I read your explanation.

I will check CR465 and CR463 as well as the voltage divider chain R444B and R444C.

Will post my results (good or bad).
--
Regards,
Bernie Murphy


Re: Tek 545A Scope

David Kuhn
 

" One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing."

O am printing this out and will investigate this in the days that come;
thank you.

Dave

On Tue, Jun 8, 2021 at 6:05 PM Dave Wise <david_wise@phoenix.com> wrote:

Send me your address off-list and I’ll mail you three new rubber mounts.
I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70
years after manufacture. You’ve already weathered the main risk, which is
blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film
and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy
impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can
absorb water if stored in a humid location, but a few hours bake should dry
it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David
Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.









Re: Tek 545A Scope

David Kuhn
 

Thank you. I just sent you an email with my UPS account information.
Don't use your own money to ship. If you want something for them, I can
send money via PayPal.

Dave

On Tue, Jun 8, 2021 at 6:05 PM Dave Wise <david_wise@phoenix.com> wrote:

Send me your address off-list and I’ll mail you three new rubber mounts.
I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70
years after manufacture. You’ve already weathered the main risk, which is
blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film
and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy
impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can
absorb water if stored in a humid location, but a few hours bake should dry
it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary,
is probably a hybrid paper-plastic dielectric. The paper side can go
lossy. Replace it and see. Any polyester or polypropylene cap will do.
Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but
that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David
Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.









Re: Tek 545A Scope

Dave Wise
 

Send me your address off-list and I’ll mail you three new rubber mounts. I bought a lifetime supply from McMaster-Carr years ago.

Typically the electrolytic caps in 500-series mainframes are fine, even 70 years after manufacture. You’ve already weathered the main risk, which is blowing the fuse on the first turn-on after years of idleness.
Most of the other caps in A-suffix instruments are ceramic or plastic film and will outlive you.

Late 500-series instruments, notoriously the 547, have lossy epoxy impregnant in the HV transformer. The only cure is a rewind.
Your 545A predates that, your transformer contains beeswax. These can absorb water if stored in a humid location, but a few hours bake should dry it out like new.

One other thing to try. C808, the 1nF cap that resonates the HV primary, is probably a hybrid paper-plastic dielectric. The paper side can go lossy. Replace it and see. Any polyester or polypropylene cap will do. Sometimes the 500pF “doorknob” ceramic caps in the tripler will fail, but that’s usually a dead short, not what you’re seeing.

HTH,
Dave Wise

From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David Kuhn via groups.io
Sent: Tuesday, June 08, 2021 1:26 PM
To: TekScopes@groups.io
Subject: [TekScopes] Tek 545A Scope

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.


Tek 545A Scope

David Kuhn
 

I recently acquired a 545A. It was quite a mess. I published some
pictures of it on the OLD Tek Scope forum on Facebook.

The Type D plugin was really a mess. I had to replace literally every
small wire! Every small wire. The amplifier chassis is mounted on
deteriorated rubber balloon mounts which, maybe in shipping, caused every
small wire to break off. With the help of the schematics from TekWiki, I
rewired that module this morning and it actually works now!

Anyway, the fan was seized, but that was easily fixed. What was not is the
rubber mounts are all crumbled and the blades very much bent. I used WD40
and after spinning it with 120 volts applied it can spin quite well (except
for the bent blades). What do people usually do to remount these fans? I
could just use screws and maybe some soft rubber washers, but I do not have
rubber stand-offs. Can you get them?

Without the fan installed. It now turns on and seems to work. The
calibrator switch took a shot of Deox 5 to get the calibrator working.
Monitoring with another scope, it is spot on with its amplitude output.

The Type D module, even with my re-wiring is damn close to spot on.

The trace is bright and very sharp. Very good CRT.

And then it blooms, starts to dim and goes away. Sounds like a high
voltage transformer?

With a floor fan on the bench pointed into the scope (it really puts out a
lot of air), it ran for over an hour before I shut it down.

What are the odds that fixing the main fan, or installing a replacement,
will keep it running? Without the fan, I am guessing it went maybe 5
minutes, maybe a little more, before blooming and losing the trace.

Also, I replaced zero caps so far. Boy does it have a huge amount of large
can caps. Do you guys typically replace them all or only as needed? The
trace has ZERO ripple or pulsations on it. The Square wave was fairly
perfect,

I had fun with this repair, so far, but find that those 4 divisions are
going to be very limiting for usage. I really thought this was a 547 when
I grabbed it all excited and then "Waaa Waaa waaaa" when I realized the
four divisions. LOL I'll trade this for a 547 with a good hiv xfrmr - LOL
(yea right).

Anyway, I hope that someone(s) can give me some directions to my questions
above. I've been lurking a long time for a 500 series scope to fix up; I
finally have one.


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

On Tue, Jun 8, 2021 at 03:55 PM, chipbee40 wrote:


I found in my workshop notes that I had a 2230 stuck on 2sec Timebase readout,
the notes stated the cause was dirty contacts on 1k/4k switch and roll/scan
switch. I'd guess I either replaced the switches or deoxited them first maybe.
It's striking that your scope had the same symptom as originally in Federico's scope.
In Store mode the 1k/4k switch is responsible for supplying the proper 1k/4k REF voltages to HOR REF, so that's a good point. As it happens Federico checked HOR REF voltages at the timing switches and they proved correct in all time/div settings (-7.91 V at 1k and -1.52 V at 4k). In 4k mode switch contact 2 is open anyway, dirty or not. In Non-Store mode the 1k/4k REF switch is not used at all.
Also taking into account the findings in the last messages I doubt a dirty 1k/4k is the fault. But I might very well be wrong here.

Albert


Re: Added lots of hard to find FETs and MOSFETs to the Stuff page.

Ondrej Pavelka
 

That is indeed interesting, I found it ever harder for Telequipment FETs.
They used British foundry and I'm afraid all the documentation is long
lost. I managed to substitute one eventually but it was a trial and error
method supported by some not very thorough circuit theory assumptions.
Overall it's a pain in the rear because so many FETs are no longer made.

On Mon, 7 Jun 2021, 20:34 walter shawlee, <walter2@sphere.bc.ca> wrote:

So many people have been chasing hard to find FETs recently that I spent
some time digging though all our semi inventory, and posted up the ones I
thought might be useful for fixing test gear and RF items. You can see them
here on the stuff day page:

https://www.sphere.bc.ca/test/stuffday.html#fets

I have put the Tek parts there too (and I have more to post this week,
also HP parts). I will try and make sure there is a rich assortment there
to look through. I also added three interesting FET substitution guides at
the top of the section, to help you find a replacement for that toasted
part. There are 2N4000/500 series parts, J-series parts, and M-series
parts, plus Tek 151-1xxx parts so far. I also have siliconix ultra low
leakage current diodes and CL diodes I will add in shortly.

all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.
https://www.sphere.bc.ca/test/index.html






Re: Problems with t935a HV supply

Ozan
 


I am still contemplating a strategy to debug the T922 HV supply that is now
putting out about 9 KV yet is drawing excessive current (about 200 ma).
Scoping a live HV supply putting out 9KV is a bit tricky.

Maybe bring up on a variac? Can only run power for about 5 seconds before
magic smoke will escape from R458 due to excessive current.
--
The regulation loop around Q454 and Q446 tries to keep cathode voltage at -2000V. With a lower voltage at +100V it will try to bias Q458 harder so it may not help the high current issue.

Since you already replaced R458 and (C458?) and other components, another possibility is the HV rectifier diodes CR463 and/or CR465. If you search the forum with the query "DC restorer" you will see a lot of good information about how to test for leaky HV diodes, and recommendations. A simple diode check on a DVM is not enough, they need to be tested at a higher voltage.

Ozan


Re: WTB: Tek 576 and P6015A

Chris Wilkson
 

On Mon, Jun 7, 2021 at 10:03 AM, Jean-Paul wrote:


may have the manual, have several P6015, must it be -A ?

Jon
If you have the manual, please let me know!

I'm looking for the -A version.
I already have the P6015 (non-A).


Re: Problems with t935a HV supply

 

I am still contemplating a strategy to debug the T922 HV supply that is now putting out about 9 KV yet is drawing excessive current (about 200 ma). Scoping a live HV supply putting out 9KV is a bit tricky.

Maybe bring up on a variac? Can only run power for about 5 seconds before magic smoke will escape from R458 due to excessive current.

Any suggestions from the experts?



--
Regards,
Bernie Murphy


FS: Original Tek 576 Op/Serv Manual and Type 172 Programmable Test Fixture $US200.00 for both

Liam Perkins
 

The 576 manual is the August 1984 revision and in excellent condition.

The "Type 172 Programmable Test Fixture" for the 576 is in likewise
excellent shape.

I want to sell them as a pair, they'll ship from Calgary, AB, Canada and
UPS Ground into the ConUS I guess might run $US50-75.00, depending

The 172 comes with a programming card and I swear up and down I have a slew
of original pins and an extra couple of programming cards sitting in one
those places where I'll be -sure- to be able to locate them. They're
included once I do.

A cleaned up, OCR-d copy of the manual from the TekWiki is here:


https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/Tek_Type_172_Programmable_Test_Fixture.pdf

It being about half the size of the original, maybe someone would up' that
to the TekWiki.

PayPal pretty much works but for unknown "reasons" that I ascribe to brain
dead AI it has begun randomly withholding payments into and transfers out
of the account, so I'll ask that any payment be sent as, "Money to those
you trust" or whatever they call it these days.

Hit me off list please at sales – at – pearl-hifi – dot – com

Liam

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