Date   

Re: Tek 1480C waveform monitor vs oscope

Dale H. Cook
 

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
https://plymouthcolony.net/starcityeng/index.html


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

John Griessen
 

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.


Re: Tektronix P6202 FET voltage probe tip problem

GeorgeP
 

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.


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

Jim Ford
 

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

-------- Original message --------From: Raymond Domp Frank <hewpatek@gmail.com> Date: 4/17/19 7:43 AM (GMT-08:00) To: TekScopes@groups.io 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


Re: Tek 1480C waveform monitor vs oscope

Harvey White
 

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



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.

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