Date   

C1001/2 vid' cams for the 11301/2

Bill Perkins <sales@...>
 

Anyone have any experience with these; the frame grabber board and the software are a complete mystery to me.

TIA for any help/admonition.

Bill


Re: Tektronix 475

Michael W. Lynch
 

On Thu, Oct 1, 2020 at 04:03 PM, Eric wrote:


Do you have access to a curve tracer? If so I would put VR1374 across it and
check it at its zener voltage. It sounds like the zener is acting up when
warm. But if it is an 82V Zener it sounds WAY out of spec at 66 V.
Eric,

You read my mind. Yes, I actually have both a 576 and 577. See my reply to Tom below. That "suspect" diode exhibited a "normal" zener trace then suddenly broke down and I got an almost "tunnel diode" looking trace just before the trace went straight vertical. Both the 576 and 577 showed similar results after a minute or two of testing. The 475 is sitting on the bench now and looks perfectly normal after about 30 minutes of running.

--
Michael Lynch
Dardanelle, AR


Re: Tektronix 475

Tom Lee
 

Sounds like you nailed it -- great job! It's always nice to have a hangar queen to provide substitute parts for quick troubleshooting. High-voltage Zeners can suffer from unstable surface breakdown, leading to "crazy" I-V curves. Sounds like your Zener has not aged gracefully (then again, who among us does?).

Enjoy that 475. It's a fine scope!

--Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 10/1/2020 14:09, Michael W. Lynch via groups.io wrote:
On Thu, Oct 1, 2020 at 03:30 PM, Tom Lee wrote:

A not uncommon problem that causes the behavior you describe is cathode-grid1
leakage. If you preclude the usual external circuit causes, then it could very
well be a crt problem. If you still have the other crt, you could do a quick
swap back and see if the problem disappears.

There are ways to fix crts with this problem but let’s hold off on that for
now.
Tom,

Thanks for your kind reply. I may have answered my own question. After writing that post, I thought that I might actually be following or understanding Chuck's explanation and that I might have a bad 82V Zener or a bad capacitor. Since I had a parts scope (the one that the CRT came from) I went out and pulled C1373 and VR1374 from that unit and installed them into my "malfunctional" unit. I am testing now, but the issue seems to be resolved. In addition, I put the unknown or "Bad" VR1374 into my Type576 and 577 curve tracers. In both cases, the component would show a normal Zener curve, then suddenly break down into a crazy looking curve (looked almost like a tunnel diode curve). Not sure what was going on, however, both the 576 and 577 showed the same results.
Tom


Re: Tektronix 475

Eric
 

Yep defiantly a bad zener. I had a 140V one do that at take out the negative power section on a 5200A I would imaging this would be aggravated by heat, IE cooling it off would make it behave warming it up and it goes nuts. Glad it is just a zener and not a tube.

On 10/1/2020 5:09 PM, Michael W. Lynch via groups.io wrote:
On Thu, Oct 1, 2020 at 03:30 PM, Tom Lee wrote:

A not uncommon problem that causes the behavior you describe is cathode-grid1
leakage. If you preclude the usual external circuit causes, then it could very
well be a crt problem. If you still have the other crt, you could do a quick
swap back and see if the problem disappears.

There are ways to fix crts with this problem but let’s hold off on that for
now.
Tom,

Thanks for your kind reply. I may have answered my own question. After writing that post, I thought that I might actually be following or understanding Chuck's explanation and that I might have a bad 82V Zener or a bad capacitor. Since I had a parts scope (the one that the CRT came from) I went out and pulled C1373 and VR1374 from that unit and installed them into my "malfunctional" unit. I am testing now, but the issue seems to be resolved. In addition, I put the unknown or "Bad" VR1374 into my Type576 and 577 curve tracers. In both cases, the component would show a normal Zener curve, then suddenly break down into a crazy looking curve (looked almost like a tunnel diode curve). Not sure what was going on, however, both the 576 and 577 showed the same results.
Tom


Re: Tektronix 475

Michael W. Lynch
 

On Thu, Oct 1, 2020 at 03:30 PM, Tom Lee wrote:


A not uncommon problem that causes the behavior you describe is cathode-grid1
leakage. If you preclude the usual external circuit causes, then it could very
well be a crt problem. If you still have the other crt, you could do a quick
swap back and see if the problem disappears.

There are ways to fix crts with this problem but let’s hold off on that for
now.
Tom,

Thanks for your kind reply. I may have answered my own question. After writing that post, I thought that I might actually be following or understanding Chuck's explanation and that I might have a bad 82V Zener or a bad capacitor. Since I had a parts scope (the one that the CRT came from) I went out and pulled C1373 and VR1374 from that unit and installed them into my "malfunctional" unit. I am testing now, but the issue seems to be resolved. In addition, I put the unknown or "Bad" VR1374 into my Type576 and 577 curve tracers. In both cases, the component would show a normal Zener curve, then suddenly break down into a crazy looking curve (looked almost like a tunnel diode curve). Not sure what was going on, however, both the 576 and 577 showed the same results.
Tom

--
Michael Lynch
Dardanelle, AR


Re: Tektronix 475

Eric
 

Do you have access to a curve tracer? If so I would put VR1374 across it and check it at its zener voltage. It sounds like the zener is acting up when warm. But if it is an 82V Zener it sounds WAY out of spec at 66 V.

On 10/1/2020 4:13 PM, Michael W. Lynch via groups.io wrote:
On Thu, Aug 13, 2020 at 09:33 AM, Chuck Harris wrote:

Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
Chuck,

I know, this is an old post and an often discussed topic.

I have a similar problem. I am working on a 475. This one had a bad CRT a broken support rod inside the CRT and a tilted trace. I have located another CRT and have installed it. I have set the grid bias, which seems to agree with the manual. No more Tilted trace. The scope works fine when you first start it up, including the Z axis amp input on the back. However, after about 20-30 minutes, the CRT intensity goes "full Bright". Z-Axis input stops affecting the trace, The CRT Trace or dot is also erratic, with the intensity changing in a random fashion from off to dim to full on bright with lots of blooming (it is mostly bright during these times). Intensity control seems to effect the brightness, but will only make the trace brighter than it is at the minimum setting, so intensity control makes it either Bright or Brighter with blooming and loss of sharpness. Focus and Astig controls work as expected when cold and with a super bright trace.

I must admit, I do not fully understand the DC Restorer. I have been reading these and other posts on the subject.

Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.
YES! Testing across VR1374 I get about 66VDC. This seems at odds with your statement quoted above. This is with the + lead on the band side and the - lead on the opposite end of the diode. Reversing the leads gives a negative voltage of similar potential. So I have "Low" voltage and something like you are describing below, correct?

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
I was expecting 82Volts but perhaps I am not measuring this correctly? From your statement, 60-66VDC would put me in the "blindingly bright range", correct?

Is it possible that this CRT has issues?

or

Would you say that the zener (VR1374) and related capacitor (C1373) could be breaking down?

CR1373 and VR1374 check "good" with a conventional diode check, using a DVM. Both show infinity one direction and .576 VDC in the other.

Like I stated previously, the scope works OK for the first 15-20 cold minutes of operation. After that it all goes nuts.

Your thoughts?


Re: Tektronix 475

Tom Lee
 

A not uncommon problem that causes the behavior you describe is cathode-grid1 leakage. If you preclude the usual external circuit causes, then it could very well be a crt problem. If you still have the other crt, you could do a quick swap back and see if the problem disappears.

There are ways to fix crts with this problem but let’s hold off on that for now.

Tom

Sent from my iThing, so please forgive brevity and typos

On Oct 1, 2020, at 13:13, Michael W. Lynch via groups.io <mlynch003=yahoo.com@groups.io> wrote:

On Thu, Aug 13, 2020 at 09:33 AM, Chuck Harris wrote:


Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
Chuck,

I know, this is an old post and an often discussed topic.

I have a similar problem. I am working on a 475. This one had a bad CRT a broken support rod inside the CRT and a tilted trace. I have located another CRT and have installed it. I have set the grid bias, which seems to agree with the manual. No more Tilted trace. The scope works fine when you first start it up, including the Z axis amp input on the back. However, after about 20-30 minutes, the CRT intensity goes "full Bright". Z-Axis input stops affecting the trace, The CRT Trace or dot is also erratic, with the intensity changing in a random fashion from off to dim to full on bright with lots of blooming (it is mostly bright during these times). Intensity control seems to effect the brightness, but will only make the trace brighter than it is at the minimum setting, so intensity control makes it either Bright or Brighter with blooming and loss of sharpness. Focus and Astig controls work as expected when cold and with a super bright trace.

I must admit, I do not fully understand the DC Restorer. I have been reading these and other posts on the subject.

Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.
YES! Testing across VR1374 I get about 66VDC. This seems at odds with your statement quoted above. This is with the + lead on the band side and the - lead on the opposite end of the diode. Reversing the leads gives a negative voltage of similar potential. So I have "Low" voltage and something like you are describing below, correct?

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
I was expecting 82Volts but perhaps I am not measuring this correctly? From your statement, 60-66VDC would put me in the "blindingly bright range", correct?

Is it possible that this CRT has issues?

or

Would you say that the zener (VR1374) and related capacitor (C1373) could be breaking down?

CR1373 and VR1374 check "good" with a conventional diode check, using a DVM. Both show infinity one direction and .576 VDC in the other.

Like I stated previously, the scope works OK for the first 15-20 cold minutes of operation. After that it all goes nuts.

Your thoughts?


--
Michael Lynch
Dardanelle, AR





Re: Tektronix 475

Michael W. Lynch
 

On Thu, Aug 13, 2020 at 09:33 AM, Chuck Harris wrote:


Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
Chuck,

I know, this is an old post and an often discussed topic.

I have a similar problem. I am working on a 475. This one had a bad CRT a broken support rod inside the CRT and a tilted trace. I have located another CRT and have installed it. I have set the grid bias, which seems to agree with the manual. No more Tilted trace. The scope works fine when you first start it up, including the Z axis amp input on the back. However, after about 20-30 minutes, the CRT intensity goes "full Bright". Z-Axis input stops affecting the trace, The CRT Trace or dot is also erratic, with the intensity changing in a random fashion from off to dim to full on bright with lots of blooming (it is mostly bright during these times). Intensity control seems to effect the brightness, but will only make the trace brighter than it is at the minimum setting, so intensity control makes it either Bright or Brighter with blooming and loss of sharpness. Focus and Astig controls work as expected when cold and with a super bright trace.

I must admit, I do not fully understand the DC Restorer. I have been reading these and other posts on the subject.

Have you checked that VR1374 has 82V across it? That 82V puts the grid
bias control into the range where the grid is in the cutoff region for
the CRT.
YES! Testing across VR1374 I get about 66VDC. This seems at odds with your statement quoted above. This is with the + lead on the band side and the - lead on the opposite end of the diode. Reversing the leads gives a negative voltage of similar potential. So I have "Low" voltage and something like you are describing below, correct?

High voltage zener's and the capacitors that parallel them often start
to break down at too low of a voltage... they become leaky... and that
would put your CRT grid into the blindingly bright range.
I was expecting 82Volts but perhaps I am not measuring this correctly? From your statement, 60-66VDC would put me in the "blindingly bright range", correct?

Is it possible that this CRT has issues?

or

Would you say that the zener (VR1374) and related capacitor (C1373) could be breaking down?

CR1373 and VR1374 check "good" with a conventional diode check, using a DVM. Both show infinity one direction and .576 VDC in the other.

Like I stated previously, the scope works OK for the first 15-20 cold minutes of operation. After that it all goes nuts.

Your thoughts?


--
Michael Lynch
Dardanelle, AR


Re: TDS 684A needs recapping?

Jokken Feldhaar
 

Hi,

I've had this exactly with a 684, about half an inch radius around the
SMT Lytics showed oxidization, it took me 2 days to safely unsolder the
72 capacitors in this unit without harming the pads. Installing the new
ones was a lot faster ;-)

I also had to change some of the ICs of the ACQ Board due to oxidated
pins on them, mostly TL084 (or was it 074?), and some 4051 multiplexers.

That was really a heap of work, but in order to save a 684 I considered
it time well spent!

Cheers, Jochen DH6FAZ

Am 30.09.2020 um 11:55 schrieb kora:

never seen tds6xx with recap required. test is easy: with heat fan at 380 *C desolder one of 5V caps (say SRAM area) from acqisition board. if it desolders without erruprion (not serious, but wear glasses anyway) - just place it again there and forget about recapping. it was relatively small 5xx party with leaky caps, many people suffered from it, but it was before 6xx.


Re: Ot 345kv substation walkthrough

greenboxmaven
 

Those people are exceptionally nimble and brave, they earn ever penny they get. The greatest danger, however, is probably not the high voltage, but rather the helicopter. Hovering at that low altitude with zero forward speed means a slim chance to clear the power lines, enter autorotation, and make a successful landing if something goes wrong. I have had a few helicopter lessons, and the scariest part is during take off when you have lifted off and don't yet have much forward speed . Low altitude is maintained until you do, but it is still risky.

Bruce Gentry, KA2IVY

On 10/1/20 1:13 PM, Greg Muir via groups.io wrote:
It's time to put on your Faraday suit and go to work....

https://www.youtube.com/watch?v=m0MiK4Jnx4s

Greg





Re: Shipping Scopes

John Williams
 

Leo thanks for the info. Now days I am mostly a buyer so I see it from that point of view. I hate to have to pay for the shipping to Kentucky then pay more for shipping to me. But mostly I have no choice. Of course it is always my choice to buy or not. Funny thing is that the Chinese systems work very well and are quite cheap but a bit slow. Cheers.


Re: Ot 345kv substation walkthrough

Greg Muir
 

It's time to put on your Faraday suit and go to work....

https://www.youtube.com/watch?v=m0MiK4Jnx4s

Greg


Re: 576 CT no step generator current but voltage steps OK

Albert Otten
 

Hi Ed,

Please ignore this if you tried already.
Set the left-off-right switch to off, steps to 1, base current at 10 uA steps, horizontal at base voltage 2 V/div. The base voltage choice terminates the base current in 1 M. So you should see a dot at 0 V and a dot at 10 V. If you increase the number of steps you will note compression above 12 V or so.
The test fixture is not involved, unless it leaks B to E somewhere, very unlikely in OFF position.
I don't know where base voltage is sensed internally. If you see the same check result when you choose Left or Right and short B to E there, there likely is an interruption between sense point and B terminal.

Albert

On Wed, Sep 30, 2020 at 12:48 AM, Ed Breya wrote:


I recently tried to check some transistors but found the 576 isn't delivering
base current steps. My most recent use was on some JFETs, which worked fine,
with voltage steps. I mostly do I-V checking, and seldom bipolar transistors,
so I have no idea how long ago this function crapped out.

I'll have to pull it off the bench and go through all the grief of handling
and opening up this beast and digging into the guts. Before I do, I'm
wondering if anyone has experienced this particular problem, and if maybe it's
something simple, like a pulled connector or such? Or, is there anything in
the plug-in test fixture that could cause this? It would be a lot easier to
yank the fixture and work on just that, of course. I've worked on these plenty
of times, and expect the diagnosis and repair will be OK, unless it's
something deep inside and hard to access.

Ed


Re: T912 F782

Michael W. Lynch
 

Mitchel,

I have a "parts only" T922 I will look on that board and see if I can identify the location and identity of those fuses. I do not see any of those fuses on the schematic that I am looking at.

--
Michael Lynch
Dardanelle, AR


tds540 what the error ?

 

tds540, acquisiton board, time interpolator (looks like delayed one, means ramp2), diag error is ctlConfidencDiag 3.040 <= exp <= 3.215 actual 3.{clipped out, still do not have debug interface to read full message}. What is this error about ? Who knows ?


Re: 576 CT no step generator current but voltage steps OK

William Borrero
 

I would say your best bet is to check your switch contacts which are likely
dirty. Sometimes just operating them can clear the problem. Focus on the
Step Generator section first.

On Tue, Sep 29, 2020 at 6:48 PM Ed Breya via groups.io <edbreya=
yahoo.com@groups.io> wrote:

I recently tried to check some transistors but found the 576 isn't
delivering base current steps. My most recent use was on some JFETs, which
worked fine, with voltage steps. I mostly do I-V checking, and seldom
bipolar transistors, so I have no idea how long ago this function crapped
out.

I'll have to pull it off the bench and go through all the grief of
handling and opening up this beast and digging into the guts. Before I do,
I'm wondering if anyone has experienced this particular problem, and if
maybe it's something simple, like a pulled connector or such? Or, is there
anything in the plug-in test fixture that could cause this? It would be a
lot easier to yank the fixture and work on just that, of course. I've
worked on these plenty of times, and expect the diagnosis and repair will
be OK, unless it's something deep inside and hard to access.

Ed





--
--
Best Regards,

Bill B.
Solutions that make sense.


T912 F782

Mitchel Rought <mjrought@...>
 

I recently went to use my T912 scope and no trace, found a component defective, it is labeled as F782, 1.5A 125V fast blo but has resistor color codes, not sure if it's a pico fuse or fusable resistor
it is located on the low voltage power supply board along with F742 and F743 all three look identical
these parts are not listed in the parts manual
Tectronix was no help at all, any help would be greatly appreciated
thank you

Mitchel Rought
644 Main Street
Chemung,New York 14825
607-742-5426
mjrought@hotmail.com
mitchelrought@gmail.com


Re: TDS 684A needs recapping?

 

never seen tds6xx with recap required. test is easy: with heat fan at 380 *C desolder one of 5V caps (say SRAM area) from acqisition board. if it desolders without erruprion (not serious, but wear glasses anyway) - just place it again there and forget about recapping. it was relatively small 5xx party with leaky caps, many people suffered from it, but it was before 6xx.

--
best regards,
kora.


Re: Shipping Scopes

satbeginner
 

I'm in Spain, and the eBay Global shipping program allows me sometimes to buy stuff not available in Europe.
Yes, it's pricey sometimes, but it's waay better than the import duties invented by Spanish customs.
And I know beforehand what my price will be.

Interesting to see what happens after the Brexit, because all shipments under the gsp came through the UK.

Stay safe,
Leo


Re: Shipping Scopes

Simon
 

eBay’s GBS is slow, unreliable and expensive. Unfortunately eBay almost imposes it on international vendors and unless they are aware of the problems they use it for convenience. On cross-border purchases it is best to dicker with the vendor about shipping before committing to payment. For most items, the regular postal service within Europe and between Europe and the USA is perfectly adequate. I try and avoid vendors who use it.
Simon

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