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Tek 576 step generator problem


Dave S.
 

Hello Guys,

i need help with my Tek 576.
Theres something pretty strange with the step generator... On some settings of the number of steps the lines start to flicker/jump around like something is not synced right.
I uploaded a little video where you can observe the video (first its set to 5 Steps, then i change the knob to 6 steps and the lines go crazy)

https://youtu.be/DeYiZHzLRo4

Even when its set to 5 every 2nd line of the measurement seems faulty aswell.

Did everyone of you ever experience this problem? Could it be a problem of the output stage of the step gen?

Hope someone can help me
BR,
David


-
 

Did you try cleaning the step selector switch? Does it do that in every
position?

On Sun, Jan 10, 2021 at 2:37 PM <hifi-workshop@gmx.at> wrote:

Hello Guys,

i need help with my Tek 576.
Theres something pretty strange with the step generator... On some
settings of the number of steps the lines start to flicker/jump around like
something is not synced right.
I uploaded a little video where you can observe the video (first its set
to 5 Steps, then i change the knob to 6 steps and the lines go crazy)

https://youtu.be/DeYiZHzLRo4

Even when its set to 5 every 2nd line of the measurement seems faulty
aswell.

Did everyone of you ever experience this problem? Could it be a problem of
the output stage of the step gen?

Hope someone can help me
BR,
David






Mlynch001
 

Does the unit flicker on the odd numbered settings? These things typically flicker visibly on the even numbered settings. This flicker is almost nonexistent on the odd numbered settings.
--
Michael Lynch
Dardanelle, AR


Dave S.
 

Yes i tried to clean it already.. nothing changed at all.

I just checked it again... the problem of the "jumping/unsynced" lines occurs on step-setting 2, 4, 6, 8 and 10


 

On Sun, Jan 10, 2021 at 08:36 PM, Dave S. wrote:


Theres something pretty strange with the step generator... On some settings of
the number of steps the lines start to flicker/jump around like something is
not synced right
You could try this: http://www.hakanh.com/dl/docs/hardtofind/576_mod41067.pdf
/Håkan


Chuck Harris <cfharris@...>
 

The filter capacitor for the 5V logic section is
known to be bad, almost always, with these curve
tracers. It is about 10K uf, and fairly low voltage,
and it becomes open circuit.

When the 5V supply capacitor is bad, it causes very
erratic operation.

-Chuck Harris

hifi-workshop@gmx.at wrote:

Hello Guys,

i need help with my Tek 576.
Theres something pretty strange with the step generator... On some settings of the number of steps the lines start to flicker/jump around like something is not synced right.
I uploaded a little video where you can observe the video (first its set to 5 Steps, then i change the knob to 6 steps and the lines go crazy)

https://youtu.be/DeYiZHzLRo4

Even when its set to 5 every 2nd line of the measurement seems faulty aswell.

Did everyone of you ever experience this problem? Could it be a problem of the output stage of the step gen?

Hope someone can help me
BR,
David






Jack2015
 

It looks like a "broken trace " issue to me.
Please ref to my 577 repair log:
<https://groups.io/g/TekScopes/topic/tek_577_d1_repair_b07xxxx/77914568?p=,,,100,0,0,0::recentpostdate%2Fsticky,,,100,2,0,77914568>

Please check the waveform of the staircase if you have a scope.

Jack


Dave S.
 

Hello,

thanks for your answers!
I checked already the caps and also the supply voltages (5V, 75V and 100V)... unfortunately they are all fine...

Could someone help me out and compare my waveforms with a working 576?
I wonder about 50uA and 1mA... is it normal that the steps are not even?

Following settings were made:
- Polarity: NPN
- Mode: NORM
- Steps: 5
- Offset: Zero
- Steps: PUSHED
- Step Family: REP
- Rate: 2x

Measurements were done between Emitter (ground of scope) and Base on the base fixture with a 100k resistor paralell

Step-Amplitude: .5uA with 100k resistor paralell
https://i.gyazo.com/b5c0c128f7d83f93cfd4717b9f059e86.png

Step-Amplitude: 5uA with 100k resistor paralell
https://i.gyazo.com/79f7748bd93b9e0c27f8d8fb592b972d.png

Step-Amplitude: 50uA with 100k resistor paralell (looks strange?)
https://i.gyazo.com/3e8ecf5e9e8d54e6921850650def7d1e.png

Step-Amplitude: .1mA with 100k resistor paralell (looks strange?)
https://i.gyazo.com/7e54a08c06a7cd1f93ab86ba012b966e.png

Step-Amplitude: 1mA with 100k resistor paralell
https://i.gyazo.com/c7f547d12099b3ebc8296821d6ce9b32.png


Step-Amplitude: 10mA with 100k resistor paralell
https://i.gyazo.com/b9b47285e7429b3a4336c262ed04afce.png

Step-Amplitude: 50mA with 100k resistor paralell
https://i.gyazo.com/9f1714ac9a2c6e6002c240a6492c953b.png

Step-Amplitude: .05V (no resistor)
https://i.gyazo.com/b6826ca93982bc6513520a82956b4920.png

Step-Amplitude: .5V (no resistor)
https://i.gyazo.com/e967d7b4ab8f052fa62a75b69eb72403.png

Thank you very much!
BR,
Dave


Jack2015
 

Step-Amplitude: .5V (no resistor)
https://i.gyazo.com/e967d7b4ab8f052fa62a75b69eb72403.png
The staircase looks ok! it's not broken trace issue.
The design of step generator circuit is different between 576 and 577.
In case of 577 the traces synchronize with the collector supply
4 traces per period(one trace per 90 degree).
This could be seen by the timing between collector supply and staircase.
<https://groups.io/g/TekScopes/photo/255563/29?p=Created,,,100,1,0,0>
<https://groups.io/g/TekScopes/photo/255563/30?p=Created,,,100,1,0,0>

Hope it helps.

Jack


Dave S.
 

Hi,

thanks for ur help!

What about the 50uA and 100uA (.1mA) waveform with the 100k paralell? Maybe you can check it on your 577 or someone else could check it on a 576 if it looks strange aswell.
Thank you!

David


Miguel Work
 

I will check it later with mine


-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Dave S.
Enviado el: lunes, 11 de enero de 2021 19:23
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Tek 576 step generator problem

Hi,

thanks for ur help!

What about the 50uA and 100uA (.1mA) waveform with the 100k paralell? Maybe you can check it on your 577 or someone else could check it on a 576 if it looks strange aswell.
Thank you!

David







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Miguel Work
 

Hi Jack, my measurements. Is normal, try to put a 10 k resistor

https://groups.io/g/TekScopes/photo/94656/0?p=Name,,,20,1,0,0

Max voltage in current mode seems 13V aprox., above this voltage constant current mode is not working.

Regards!

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Jack2015
Enviado el: lunes, 11 de enero de 2021 17:44
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Tek 576 step generator problem


Step-Amplitude: .5V (no resistor)
https://i.gyazo.com/e967d7b4ab8f052fa62a75b69eb72403.png
The staircase looks ok! it's not broken trace issue.
The design of step generator circuit is different between 576 and 577.
In case of 577 the traces synchronize with the collector supply
4 traces per period(one trace per 90 degree).
This could be seen by the timing between collector supply and staircase.
<https://groups.io/g/TekScopes/photo/255563/29?p=Created,,,100,1,0,0>
<https://groups.io/g/TekScopes/photo/255563/30?p=Created,,,100,1,0,0>

Hope it helps.

Jack











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Jack2015
 

Hi David,

Miguel did the tests for you,I believe this is what he wants to show us:
<https://groups.io/g/TekScopes/photo/94656/6?p=Created,,,100,1,0,0>

Jack


Dave S.
 

Hello,

thank you very much guys for your help!
So it looks like my step-gen performs ok and like Michael Lynch said it seems to be normal that the waveform flickers a bit more @ 2, 4, 6, 8 and 10 steps.

Anyway i ran into another problem (or is it a problem?!) ... Maybe someone can do another (pretty easy) check/comparison
I shorted the C and E terminal, set the vertical range to 5uA and turned up the collector supply to have 2 divisions (10uA). When i change the vertical range now from 5uA to 10uA the reading is not 10uA but suddenly almost 75uA.
Is that normal due to internal change of measurement resistor?

5uA-Range:
https://i.gyazo.com/576b1ab29cb29caf641fe9400db731a3.png

10uA-Range without changing collector supply:
https://i.gyazo.com/9b5e1be8ce8c3baf502ebb193b18ac41.png

BR,
David


Mlynch001
 

On Wed, Jan 13, 2021 at 07:10 AM, Dave S. wrote:


Anyway i ran into another problem (or is it a problem?!) ... Maybe someone can
do another (pretty easy) check/comparison
Did you get an answer to your question? I was going to check and the power went off at the house.

--
Michael Lynch
Dardanelle, AR


Dave S.
 

Hi,

unfortunately not.
Maybe you could help me and make a quick check for that issue :)

Thank you!

Dave


Miguel Work
 

Hi David,

It seems normal, mine jumps from 10 to 65uA

Regards

Miguel
-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Dave S.
Enviado el: miércoles, 13 de enero de 2021 14:11
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Tek 576 step generator problem

Hello,

thank you very much guys for your help!
So it looks like my step-gen performs ok and like Michael Lynch said it seems to be normal that the waveform flickers a bit more @ 2, 4, 6, 8 and 10 steps.

Anyway i ran into another problem (or is it a problem?!) ... Maybe someone can do another (pretty easy) check/comparison I shorted the C and E terminal, set the vertical range to 5uA and turned up the collector supply to have 2 divisions (10uA). When i change the vertical range now from 5uA to 10uA the reading is not 10uA but suddenly almost 75uA.
Is that normal due to internal change of measurement resistor?

5uA-Range:
https://i.gyazo.com/576b1ab29cb29caf641fe9400db731a3.png

10uA-Range without changing collector supply:
https://i.gyazo.com/9b5e1be8ce8c3baf502ebb193b18ac41.png

BR,
David







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