Date   

Re: 465B Horizontal Trace Issues - Help requested

Jean-Paul
 

Hello BRAVO for your effort, the 465/475/B were my main scopes in 1970s, are a great advance over the 453/454/485. (At my first job, 1968 used 454)
Brings back memories!

Tants were used everywhere at that epoch, if the current is not limited and used near rated V they do fail shorted or blow open.

The 2" service manual is a classic and highly recommend to DL the PDF version for your serial number range.

This electronic dinosaur much prefers the original bound TEK to the PDF. Look on fleabay.

Qservice in Greece, has for sale very fine reproductions.

Finally, consider to recap the PSU, the lytics dry out and seals fail, also check the fan bearings.

Many threads on recapping the 465/475/B.

Bon chance!

Jon


Re: 465B Horizontal Trace Issues - Help requested

@Sabrefencer
 

Eureka!

I just executed the idea of bypassing the 1X pot (1k ohm) - first with a jumper I had handy that I use to discharge capacitors (a 5W 1K resistor in a wire between two minigrabber probes). That brought the resistance in line with what it should be reading through the pot. Then I replaced the resistor with my Heathkit IN-3117 Decade resistance box. Even set to zero ohms, when i turned on the scope the trace was stable and only slightly compressed. Changing the resistance on the box allowed me to set the trace to any level of compression including no compression at all. I have it exactly where it should be - right to the edges of the grid (390 ohms is just about perfect). When I unplug one of the leads from the decade box, the trace immediately collapses, plug it back in and trace is perfect. Shailendra you suggested that the problem may be the pot - good call.

I do believe this confirms the 1X pot is the culprit. Shailendra you suggested that the problem may be the pot - good call. Since i have a 390 ohm 1/2W resistor and not the the pot, I think i will put in the resistor and run it for a while to see if everything else is working properly. Then when I have collected all necessary parts (pots, tants, electrolytics), and increased my skill level, take it apart, clean it and preemptively replace the usual suspects. Since a pot is just a variable resistor I can't think of any reason not to leave a fixed resistor soldered in place for a month or two. Other than this being a "kluge" repair to a precision instrument any reason not to? But if anyone can think of an electronic reason, please let me know.

I feel like the lawnmower mechanic that just "fixed" the Ferrari with a hair pin.

I will put together a BOM for pots, tants, and lytics and run it by this group.

Thanks for all the help and encouragement.

Gary


Re: 465B Horizontal Trace Issues - Help requested

Harvey White
 

That seems to indicate that the horizontal amplifier, in the x10 position, can swing enough to give you proper deflection.

This suggests that the X1 pot and the components (and perhaps switches) are faulty.

IIRC, the X1 is the default, and the X10 is switched in (and less resistance), IIRC, this is an emitter coupled difrerential amplifier, and the resistor coupling the two emitters together determines stage gain.  Switching in an X10 pot (and adjusting it properly) gives you the additional gain.

Harvey

On 10/1/2020 7:53 PM, gary@pincus4.com wrote:
Yes, in the x10 position the trace does indeed seem uncompressed. I can find the "whole" trace by moving horizontal position, i even counted # of square waves to verify.





Re: 465B Horizontal Trace Issues - Help requested

@Sabrefencer
 

Yes, in the x10 position the trace does indeed seem uncompressed. I can find the "whole" trace by moving horizontal position, i even counted # of square waves to verify.


Re: 465B Horizontal Trace Issues - Help requested

@Sabrefencer
 

Tom,

Before my last post, I photographed (as a method of marking) the x1, and x10 pots and sprayed a small amount of Deoxit under the "dial" - the pot looks like it may be sealed, so I have no idea if it penetrated, but what the heck. I worked these pots back and forth many times with the power off, and even with scope operating, but no impact on collapsed trace. I have returned them to their original position. I tried to measure the resistance across the pot and nearby resistors, but this section of the circuit has parallel paths, with other resistors, so that may be difficult. I do not see a way to remove the pot without accessing the dark side of the A4 board, which requires disassembly. Is there a way to bypass or "jump out" the pot, either with a wire or a resistor (or even by resistor decade box - which is giant discrete pot)? In the meantime I am searching Mouser for a replacement pot.

You mention bias voltages in the stage, I do not know where to check that.

Thanks Gary


Re: C1001/2 vid' cams for the 11301/2

Bill Perkins <sales@...>
 

Brian wrote:
Hi Bill , I have several of these video camera's but not the Tek frame grabber or software . I have a Cortex frame grabber which works very well and some Cortex s/w available on their website some years ago - not sure about now though . The card I am using is an ISA card so it needs an old PC, there is a PCI version of the card which might be easily found and the s/w for that was also on the website. The cards have a 9pin 'D' type connector on the bracket which allows video input and also a trigger for grabbing a frame plus a 12v output which can power the C1001/2
I have also used the cameras with a cheap USB stick used for surveillance systems and also similar ones used in video to DVD applications without much trouble. I had a great time showing my 7104 screen on a 15 inch laptop screen . There is a downside using the cameras though, whatever you do it's not much good capturing any single shot waveforms
I hope this helps a little
Brian
Yes, it does. Thx.
Any chance for a few links, save me digging high and low ?
I'd want the PCI version of any card. ISA is just -so-last century :-)

Not one to be lazy, I did some digging and found this halfway likely looking site:

http://www.imagenation.com/imagena/default.html

but I don't know what I'm after.

I'm planning to pick up a Tek 79364, a 500MHz storage unit* so fast one-shots won't be a problem and I work in audio so all that's sort of a 'who-cares' anyway.

Thx,
Bill

* Yeah Walt, I'm still in; just delayed. My daughter bought the house she wanted so I'll be out to see you real soon.


Re: Ot 345kv substation walkthrough

Greg Muir
 

It only takes a little wind gust to throw things out of whack. And nicking your tail rotor is not good either.

When working on a contract with Denver Police many years ago had a chopper take off from a helipad next to the police building in the center of town. He was just barely gaining altitude when a little wind gust came around the corner of the nearby building spinning him around and catching the tail rotor on a nearby structure. He set down rather fast and awkward missing everything else. The good side was that he walked away from it.

Greg


Re: C1001/2 vid' cams for the 11301/2

Brian
 

Hi Bill , I have several of these video camera's but not the Tek frame grabber or software . I have a Cortex frame grabber which works very well and some Cortex s/w available on their website some years ago - not sure about now though . The card I am using is an ISA card so it needs an old Pc, there is a PCI version of the card which might be easily found and the s/w for that was also on the website .The cards have a 9pin 'D' type connector on the bracket which allows video input and also a trigger for grabbing a frame plus a 12v output which can power the C1001/2
I have also used the camera's with a cheap USB stick used for surveilance systems and also similar ones used in video to DVD applications with out much trouble . I had a great time showing my 7104 screen on a 15 inch laptop screen .There is a downside using the camera's though , whatever you do its not much good capturing any single shot waveforms
I hope this helps a little 
Brian

On Thursday, 1 October 2020, 22:37:28 BST, Bill Perkins <sales@pearl-hifi.com> wrote:

    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
 

All:

Just like the Energizer Bunny, the 475 is "Still Working" and the "Tilted Trace" is banished. That 82V Zener Diode must have been the intensity problem. The "new" CRT fixed the tilt. Thanks for all the help and encouragement. I just love to see one of these old scopes come back to life.

--
Michael Lynch
Dardanelle, AR


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.

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