Re: Absurdly simple way to get contact cleaner into some Tek pots
This has been a very interesting thread on how to clean potentiometers, but there has been no mention of what happens after you get the cleaner/lubrication into the potentiometer.
Do you leave the liquids in there, and what about the residue that caused your problem to start with?
Thank you for any comments you might have!
tom jobe...
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On 4/16/2019 9:44 PM, Frank DuVal via Groups.Io wrote: I think GC Electronics made them for their contact cleaner. Long cylinder that threaded onto the mounting nut, maybe 5 inches long and necked down to a small diameter that fit the aerosol nozzle of the contact cleaner.
Check electronics magazines of the 1950s.
I see the StewMac cap advertised. Only good for short shaft pots.
Frank DuVal
On 4/16/2019 6:26 PM, John Kolb wrote:
I remember seeing in the distant past, a catalog picture of a pot/contact cleaner which threaded onto the pot threaded bushing. I guess you would then put in the cleaner/lube, and push a plunger to force the cleaner into the pot.
John
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Re: Absurdly simple way to get contact cleaner into some Tek pots
Be careful where you drill that hole. It is easy to scratch and break the resistive element. It is best to find an old discardable identical potentiometer that you can open up to see where the critical pathway is so you can avoid it. Gary On Tue, Apr 16, 2019 at 10:52 AM Richard Solomon <dickw1ksz@...> wrote: My foolproof method is to drill
a small hole on the top side at
the rear. Pump in De-Oxit Fader
Lube and seal the hole with some
black tape.
73, Dick, W1KSZ
On Tue, Apr 16, 2019 at 10:45 AM Terry Gray via Groups.Io <tlgray42=
[email protected]> wrote:
I also have restored 100's of "sealed"? noisy controls by pointing the
control shaft straight up vertically, wrapping something around the bottom
of the control to catch the excess contact CLEANER/LUBE, spray around the
base of the shaft where it goes into the control, and "pump" the shaft up
and down and give it time to "pump" the contact cleaner/lube down into the
control---remember patience is a virtue. If at first it doesn't seem to be
getting the spray down the shaft, make a dam" just below the point where
the shaft enters into the control and try spraying a little additional
cleaner/lube into that area keeping it saturated and at the same time
periodically "pumping' the shaft up and down to allow the cleaner/lube to
migrate along with capillary action down the shaft. Allow the potentiometer
shaft to remain pointed up vertically. Sometimes it can take overnight or
longer to get the cleaner/lube down into the control but I have found over
the last 50-60 years that it very, very rarely fails. Just be patient and I
think this will work for you, even for the difficult ones. I remember
setting upright on their backs some of the big monster stereos and doing
just that, especially when the potentiometer access was not readily
accessible even with the long extended flexible tubing that sometimes came
with the contact cleaner/lube or that were also available at the time. I
also remember running into some well sealed potentiometers and TV tuners
that we had to drill a small access hole into/through the metal or plastic
housing to get the cleaner/lube inside to do its job. Just be very careful
to not drill into the tuner or control doing any internal damage. I
remember disassembling throw-away pots and tuners to learn where to drill
the holes to prevent any internal damage and you could then seal the hole
up with solder or glue when you completed the cleaning/lube process. One
additional point, DO NOT use a contact cleaner with no lubricating agent in
its ingredients. Many years ago I attended a Channel Master seminar on
their contact cleaners and tuner (and switch) cleaner/lubes. The company
representative showed us under a fairly high-powered microscope a video of
what happens when you spray a contact cleaner (with no lube) on the old TV
tuner switch contacts You completely wash away all lubrication from the
individual contact points and he showed us under the microscope what
happens when you rotate the switch thru the washed contacts. It scrapes the
plating off the contacts and now being unplated in that area it is oxidizes
and you end up with intermittent high resistance contacts down the
line(with time) that play havoc with your circuit. You think that you are
"fixing" the intermittent switch contact(s) (or the intermittent internal
potentiometer wiper problem) but in reality you are totally ruining (for
the future) whatever you are so-called restoring by using a non-lubricated
spray. I wish the video that the Channel Master rep showed us was still
available>>>>it looked like a chisel scraping the plating off the contact
under the high-magnification microscope when all the lubrication had been
previously "cleaned" off the contact areas. He said DO NOT EVER use a
contact cleaner that has no lubrication in it or at least follow up the
"cleaning" process by spraying or adding some additional lubrication to the
contact points. Hope this is helpful information to some of you, it sure
was for me.
On Tuesday, April 16, 2019, 9:51:07 AM CDT, Bob Koller via Groups.Io
<testtech@...> wrote:
Try it sometime, I have literally done hundreds this way. Some last week..
-- Gary Robert Bosworth grbosworth@... Tel: 310-317-2247
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Re: Tektronix P6202 FET voltage probe tip problem
On Wed, 17 Apr 2019 08:15:35 -0700, you wrote: Thanks Harvey. I studied things a bit more and decided to give up. The FET probe is on Ebay as Parts/repair with missing probe socket. I tried to list it factually. I hate giving up but sometimes it is necessary. You're welcome. Glad to be of help. The probe is nice, good for full bandwidth on a 7A19 or 7A29. I prefer 7A29's because I think they're less prone to damage. The 7A24, which is good, has somewhat less bandwidth. Things like the 7A26 have a decent bandwidth, but still (at times) better than the average passive probe. Harvey
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On Wed, Apr 17, 2019 at 04:56 PM, Jim Ford wrote:
I've been following this thread with some interest because I have a 7B71
myself.? Planning to try it in 7904 when I get a chance.
To Jim & John: I just tried a 7B71/7B70 set in a 7904 (they were really meant for the 7704(A) but work fine in most any 7xxx mainframe). I've always found the trigger setting knob in these time bases (7B5x and 7B7x) a bit finicky in more critical situations. Triggering on a < 1 ns edge at 20, 50 and 100 ns / div. with about 4 div. signal amplitude was no problem but it wasn't difficult to have some jitter by playing with the trigger level adjustment knob. It was slightly different for different speed settings. All to be expected. Difficulty in removing the jitter with a reasonable amplitude (> 1.5 div on screen for a reasonably fast signal) and reasonable steepness of the slope would indicate a time base problem, *unless* trying to trigger too close to the amplitude extremes. Raymond
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Re: Tek 1480C waveform monitor vs oscope
On 4/17/2019 10:06 AM, NielsenTelecom wrote: I have been given this tool. I have a Tek 2246A and a Hitachi scope already. What can I do with this that I can't with the other scopes? You can look at NTSC video (old analog video) with it. It is pretty much useless for anything else as it is a specialized instrument. It was the waveform monitor of choice back in the day when I was a television Chief Engineer. Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On 4/17/19 9:43 AM, Raymond Domp Frank wrote: If you'd see the same effect with a steeper slope with a larger amplitude at the same time base speeds,*that* would mean something and would point specifically to a problem in the time base. Ok, I can try that. I'll have to get another pulse generator than the calibrator to be steeper slope. Later today.
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Re: Tektronix P6202 FET voltage probe tip problem
Thanks Harvey. I studied things a bit more and decided to give up. The FET probe is on Ebay as Parts/repair with missing probe socket. I tried to list it factually. I hate giving up but sometimes it is necessary.
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
I've been following this thread with some interest because I have a 7B71 myself.? Planning to try it in 7904 when I get a chance.? With 7A26 and new-to-me 7A11's.? Maybe this weekend.? I will post my results.?Jim Ford?Sent from my Verizon, Samsung Galaxy smartphone
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-------- Original message --------From: Raymond Domp Frank <hewpatek@...> Date: 4/17/19 7:43 AM (GMT-08:00) To: [email protected] Subject: Re: [TekScopes] 7B71 time base jittering at 50ns/div, but not other speeds. On Wed, Apr 17, 2019 at 03:46 PM, John Griessen wrote:>> 20 ns is usually solid>You seem to say that it too sometimes displays the same behaviour, which is only natural, as may be deduced from what I wrote earlier.You are looking at a very slow ramp/edge, triggering a time base at about its top speed at almost top amplitude level with a vertical sensitivity of only 2 mV / div.Such a slow ramp provides very little information in your measurement setup. It may be an interesting experiment.It is possible that some imperfect/varying contact causes the effective trigger voltage to vary by a few 100 microvolts, which would cause the behaviour that you see. If you'd see the same effect with a steeper slope with a larger amplitude at the same time base speeds, *that* would mean something and would point specifically to a problem in the time base.Raymond
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Re: Tek 1480C waveform monitor vs oscope
On Wed, 17 Apr 2019 07:06:19 -0700, you wrote: I have been given this tool. I have a Tek 2246A and a Hitachi scope already. What can I do with this that I can't with the other scopes? I have never done anything with video nor intend to. Also, the trace is hiding deep lower left of CRT. Can't get it out of there. If you're doing anything with baseband video, such as CCTV cameras for surveillance systems, video tape recorders, etc., then you'll want this. It looks at very specific things on the video waveform with an ease that is hard to duplicate on most oscilloscopes unless they have some very specific TV signal processing/filters built in. Having said that, this is the old standard 450 or so line resolution, analog video, 75 ohms, 1.4 v p-p video that uses either BNC, SO-239, or RCA jacks (on consumer equipment). Generally not found as much as you'd think. If you never intend to do anything with video, then it won't be of much use to you. As has been mentioned, it's not a general purpose scope. Harvey
NielsenTelecom
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On Wed, Apr 17, 2019 at 03:46 PM, John Griessen wrote:
20 ns is usually solid
You seem to say that it too sometimes displays the same behaviour, which is only natural, as may be deduced from what I wrote earlier. You are looking at a very slow ramp/edge, triggering a time base at about its top speed at almost top amplitude level with a vertical sensitivity of only 2 mV / div. Such a slow ramp provides very little information in your measurement setup. It may be an interesting experiment. It is possible that some imperfect/varying contact causes the effective trigger voltage to vary by a few 100 microvolts, which would cause the behaviour that you see. If you'd see the same effect with a steeper slope with a larger amplitude at the same time base speeds, *that* would mean something and would point specifically to a problem in the time base. Raymond
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Re: Tek 1480C waveform monitor vs oscope
The 1480 series are excellent video waveform monitors but not useful as general purpose scopes. Of limited use now, even as waveform monitors since they only do standard definition analogue video, something that's totally obsolete in the professional world and increasingly so elsewhere. One use might be to somebody restoring a historic video installation of that period.
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Tek 1480C waveform monitor vs oscope
I have been given this tool. I have a Tek 2246A and a Hitachi scope already. What can I do with this that I can't with the other scopes? I have never done anything with video nor intend to. Also, the trace is hiding deep lower left of CRT. Can't get it out of there.
NielsenTelecom
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On 4/17/19 4:53 AM, Raymond Domp Frank wrote: The jitter is constant at all trigger levels on 50ns/div, but not other
speeds.
With "not at other speeds" you mean not at faster speeds either?
Yes, of the four fastest speeds, 50ns/div is always jittery +/- 1/2 div. 20 ns is usually solid, with maybe 1/2 trace width jitter. 100ns/div and 200ns/div randomly can have excess jitter. These show this symptom: OK (100ns/div) random (50ns/div) good (20ns/div) A 7B70 does not do this, has maybe 1/2 trace width jitter up to fastest, (for it), 20 ns/div 7B10, 7B15, 7B92A do not do this either.
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On 4/17/19 4:53 AM, Raymond Domp Frank wrote: The jitter is constant at all trigger levels on 50ns/div, but not other
speeds.
With "not at other speeds" you mean not at faster speeds either?
Yes, of the four fastest speeds, 50ns/div is always jittery +/- 1/2 div. 20 ns is usually solid, with maybe 1/2 trace width jitter. 100ns/div and 200ns/div randomly can have excess jitter. A 7B70 does not do this, has maybe 1/2 trace width jitter up to fastest, (for it), 20 ns/div 7B10, 7B15, 7B92A do not do this either.
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from Tim P (UK)
WTB 311-1485-00 dual pot 100K + 2K
anyone got one for sale ? (nothing on Qservice or Testequip)
thanks
Tim
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Re: 475A : excessive jitter on delayed sweep
On Wed, Apr 17, 2019 at 01:23 PM, Alberto I2PHD wrote:
If instead it indicates the positive side,
It does indeed. No assembly error. You would have noticed or would notice soon if incorrectly mounted... Raymond
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Re: Where can I find TDS600C Field Adjustment Software?
@Raymond
Thanks for the reply and for sending the TDS600B software, much appreciated.
@Zenith
I have sent a PM to you offlist - thanks again for the reply.
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Re: Where can I find TDS600C Field Adjustment Software?
On Tue, Apr 16, 2019 at 10:46 PM, @Arcticgeek wrote:
I have everything I need now in order to do the calibration except the TDS600C
Field Adjustment Software.
I doubt that the B-model software will work on a C-model. Reply to me off list and I'll mail it to you. /H?kan
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Re: 475A : excessive jitter on delayed sweep
On 2019-04-16 16:35, Alberto I2PHD wrote: There is a suspect tantalum capacitor, which I did not replace, namely
C933, which is in the path that brings working voltage to the Delay Time Position control.... just as good measure, I
will replace that also... Problem fixed. I replaced that suspect capacitor with a 4.7uF, 100V electrolytic, and now the delay time after which the B sweep starts is rock stable... Now I have a suspect, which maybe somebody could confirm or deny... look at this photo of the replaced cap : Should the mark indicate the negative side of the cap, then it was soldered in reverse, with the marked side connected to +14V.... If instead it indicates the positive side, then no manufacturing errors....? I am not much familiar with the markings of the tantalum caps.... In any case, now my 475A is perfectly working, and this is what counts... :-) -- /*73 Alberto I2PHD* Keyboard not found : Press F1 to continue/
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Re: 7B71 time base jittering at 50ns/div, but not other speeds.
On Wed, Apr 17, 2019 at 05:59 AM, John Griessen wrote:
The jitter is constant at all trigger levels on 50ns/div, but not other
speeds.
With "not at other speeds" you mean not at faster speeds either? Use enough brightness to judge that, since the jitter may not be evenly spread. Related to what I said before about trigger level: Do not expect a jitterless display with an on-screen relatively high-speed slope of significantly less than 45 degrees at the trigger point. The 'scope and time base aren't made for that and the image contains little information. You can't decide if you're seeing timebase jitter, trigger jitter or jitter in your signal. Read up on triggering in general and with regard to your setup, especially minimum size of the on-screen signal for reliable triggering at a certain horizontal speed. I really have not seen or read any indication that something's wrong with your 'scope or time base. Raymond
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Gary Robert Bosworth
Raymond Domp Frank
Dale H. Cook
GeorgeP
ppppenguin
zenith5106
Alberto I2PHD