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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


Re: Tek 1480C waveform monitor vs oscope

ppppenguin
 

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.


Tek 1480C waveform monitor vs oscope

nielsentelecom@sbcglobal.net
 

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


Re: 7B71 time base jittering at 50ns/div, but not other speeds.

John Griessen
 

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:

https://www.ecosensory.com/tek/tek-7B71_trouble-6.jpg OK (100ns/div)
https://www.ecosensory.com/tek/tek-7B71_trouble-7.jpg random (50ns/div)
https://www.ecosensory.com/tek/tek-7B71_trouble-8.jpg 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.


Re: 7B71 time base jittering at 50ns/div, but not other speeds.

John Griessen
 

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.


WTB 311-1485 dual pot.

Tim Phillips
 

from Tim P (UK)
WTB 311-1485-00 dual pot 100K + 2K
anyone got one for sale ? (nothing on Qservice or Testequip)
thanks
Tim


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


Re: Where can I find TDS600C Field Adjustment Software?

@Arcticgeek
 

@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.


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.
/Håkan


Re: 475A : excessive jitter on delayed sweep

Alberto I2PHD
 

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 :

http://www.i2phd.org/public/tantalum2.2uF.jpg

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/


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


Re: Absurdly simple way to get contact cleaner into some Tek pots

Tim Phillips
 

from Tim P (UK)
I wonder if those stand-off bushes used to space pots off front panels
(particularly 500-series plug-ins)
would suffice.
Tim

On Wed, 17 Apr 2019 at 07:26, Daveolla <grobbins@netflash.net> wrote:

Or, in a pinch get a short tube, rubber, silicone, a striped off
jacket from cable, heat shrink etc that fits over snugly on the
pots threads. Then just add some cleaner drops in the tube or drip
some around the shaft before putting the tube in place. Then as
someone said before "just put your lips together and blow"

Dave




Re: Absurdly simple way to get contact cleaner into some Tek pots

Daveolla
 

Or, in a pinch get a short tube, rubber, silicone, a striped off 
jacket  from cable, heat shrink etc that fits over snugly  on the 
pots threads. Then just add some cleaner drops in the tube or drip 
some around the shaft  before putting the tube in place. Then as 
someone said before "just put your lips together and blow"

Dave


Re: Absurdly simple way to get contact cleaner into some Tek pots

Frank DuVal
 

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


Re: 7B71 time base jittering at 50ns/div, but not other speeds.

John Griessen
 

On 4/16/19 8:00 PM, Raymond Domp Frank wrote:
Adjust the trigger voltage very carefully and you'll see the trace (slope) shift horizontally. The jitter will be less with some settings.
No, this is a symptom I am asking for help with. The jitter is constant at all trigger levels on 50ns/div, but not other speeds.


Re: Absurdly simple way to get contact cleaner into some Tek pots

Jared Cabot
 

I found them on ebay, I might get a set for my restorations.

https://www.ebay.com/sch/i.html?_nkw=guitar+pot+cleaning+cap

Thanks for the heads up! :)


Re: 7B71 time base jittering at 50ns/div, but not other speeds.

 

On Wed, Apr 17, 2019 at 01:05 AM, John Griessen wrote:


That is not normal, is it?
Oh yes, it is absolutely normal. The slope should be much steeper for measuring pulse widths or slopes: Consider the fact that with your setup a minimal difference in trigger voltage means a relatively large difference in time. As a result, you're mostly "measuring" trigger voltage. With a steep slope, the trigger voltage is not as critical.
The "jitter" that you're seeing in the slope is a result of the fact that even an extremely small variation in trigger voltage (nothing is perfect) causes a horizontal shift of the image. Adjust the trigger voltage very carefully and you'll see the trace (slope) shift horizontally. The jitter will be less with some settings.

Raymond


Re: Tektronix P6202 FET voltage probe tip problem

Harvey White
 

On Tue, 16 Apr 2019 17:12:11 -0700, you wrote:

George-
I have been thinking of where the wire may have originated, I looked at
my 6202A and realized it might be the "feed through" wire to the
replaceable tip.
To me, that would make sense if the wire went through to a contact
inside the socket.

The sockets I have are sealed at the bottom.


If that is the case then the (working part) tip will obviously not have
a connection when assembled. I am thinking the barrel is spun/threaded
on to the body and after many on/off assemblies that wire was left in
the circuit board receptacle, one MIGHT be able to re-use the old broken
tip backwards as a replacement socket after removing the plastic from
broken tip. better look down the inside of the barrel to see if the feed
through is still there. If not then now there are two issues. one
removal of wire from socket and replacement of feed through.
If they did it that way, then it makes sense. Not sure that they did.
another explanation may be that someone broke the tip (at first), then
decided that they wanted the probe to work, so they stuffed a wire
into it.

That broke...

Harvey


Renée
ps i am looking for the slip on retractable hook is someone has an
orphan....pm me. k6fsb.1 at the gmail thing

On 2019-04-15 9:11 a.m., GeorgeP wrote:
I've added another pic of the tip with the socket now removed. https://groups.io/g/TekScopes/photo/89499/0?p=Created,,,20,2,0,0
Keystone makes similar sockets. 0.032" seems to be a popular size. https://www.keyelco.com/userAssets/file/M65micro-jacks.pdf
Now that i have the socket off the board there is less hazard to the probe while I work on the socket.
I will definitely need to jig it to solder it back.
The teflon washer just pops off the smaller end of the socket.
Thanks to everyone for interest and support! :)
George






Re: Tektronix P6202 FET voltage probe tip problem

Renée
 

George-
I have been thinking of where the wire may have originated, I looked at my 6202A and realized it might be the "feed through" wire to the replaceable tip.
If that is the case then the (working part) tip will obviously not have a connection when assembled. I am thinking the barrel is spun/threaded on to the body and after many on/off assemblies that wire was left in the circuit board receptacle, one MIGHT be able to re-use the old broken tip backwards as a replacement socket after removing the plastic from broken tip. better look down the inside of the barrel to see if the feed through is still there. If not then now there are two issues. one removal of wire from socket and replacement of feed through.
Renée
ps i am looking for the slip on retractable hook is someone has an orphan....pm me. k6fsb.1 at the gmail thing

On 2019-04-15 9:11 a.m., GeorgeP wrote:
I've added another pic of the tip with the socket now removed. https://groups.io/g/TekScopes/photo/89499/0?p=Created,,,20,2,0,0
Keystone makes similar sockets. 0.032" seems to be a popular size. https://www.keyelco.com/userAssets/file/M65micro-jacks.pdf
Now that i have the socket off the board there is less hazard to the probe while I work on the socket.
I will definitely need to jig it to solder it back.
The teflon washer just pops off the smaller end of the socket.
Thanks to everyone for interest and support! :)
George



Re: 7B71 time base jittering at 50ns/div, but not other speeds.

John Griessen
 

On 4/16/19 4:36 PM, Raymond Domp Frank wrote:
Back to your issue: The horizontal starting position on the screen is never an indication of time with regard to the trigger moment, especially at different higher-speed sec/div. settings.
OK, thanks for explaining that the different starting positions are as designed. Please look at this trace though:

https://www.ecosensory.com/tek/tek-7B71_trouble-7.jpg

Did you see the 1 div wide blur of starting positions that is a random process happening? This can happen in several
sweep speed knob positions and is drastically different than the others, and not very useful for measuring pulse widths against.

That is not normal, is it?

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