Atten ADS1152CA trace issue

[NEELIMAVUNGAL]

Hi all, i am new to this forum. I have an issue with my atten ads1152ca scope. I rarely used it. while working it suddeny stop tracing. then i did a self calibration but it stuck on calibrating channel 2. I suspect the probe and put a resister inside the bnc jack wth bare hand, but there is no noise trace. what could be the problem. any idea. please help me

[NEELIMAVUNGAL]

  Nobody answered the question. look at the photos. I did not connected probes but the cursor is not in the middle position.
https://youtu.be/KqNTTcAdRTM

[tautech]

Try Default.
Then press V pos for each channel so to zero their positions.

[NEELIMAVUNGAL]

Try Default.
Then press V pos for each channel so to zero their positions.

thank you for the comment. I have already tried even factory default. the result is same.

[NEELIMAVUNGAL]

I think this is a hardware issue. if so, what could be the problem,

[Microcheap]

Is that a leaked electrolytic capacitor on your first picture? Try to probe the test points (TP) of the power supply rails to see if they are ok, normally there is a silk screen on the board close to the TP with the nominal value.

[NEELIMAVUNGAL]

Is that a leaked electrolytic capacitor on your first picture? Try to probe the test points (TP) of the power supply rails to see if they are ok, normally there is a silk screen on the board close to the TP with the nominal value.

Thank you sir, that is not a leaky capacitor.but is gum on it. and there is no voltage values on silkscreen. but I tested all the test points according to the service Manuel of a similar sigilent board and the TP voltages are OK.

[NEELIMAVUNGAL]

Actually I have tested all the power rails and capacitors including bypass capacitors of each power rail. I do not know the signal input mechanism of a dso. there is an ad8370 variable gain amp in the signal input circuit. if you know more about the functions and voltage values of that chip, please help me.I have referred the datasheet but not fully understood.
 

[NEELIMAVUNGAL]

Look at the voltages. is this normal

[NEELIMAVUNGAL]

Hello all, please see the picture what is that marked chip 6552. Is that op amp or mosfet. please  help.

[mikerj]

Possibly an LMH6552, a high bandwidth differential amplifier.

[Kleinstein]

Unless the trace is really out and can not be shifted back (with y-position) I don't think this is really an HW issue. It looks more like lost adjustment data. Normally there should be a software way to readjust the zero position.

[NEELIMAVUNGAL]

Possibly an LMH6552, a high bandwidth differential amplifier.

Thanks, let me try to find out.

[NEELIMAVUNGAL]

Unless the trace is really out and can not be shifted back (with y-position) I don't think this is really an HW issue. It looks more like lost adjustment data. Normally there should be a software way to readjust the zero position.

thanks for the replay, It is not only a trace positioning issue, but I can not trace except in 500 mv division on both channels!

[tautech]

but I can not trace except in 500 mv division on both channels!

Ah, so we finally have a good symptom.

The V/div attenuation settings are made in the front end input stages.
So you need follow the signal input path near the BNC's here:



Do any relays click when adjusting V/div ?

[NEELIMAVUNGAL]

Do any relays click when adjusting V/div ?

yes, I can hear clicking relays while changing vertical pitch.
I noticed some voltage difference in two input stages and the source of the difference is from the chip 6552.

[Kleinstein]

With both channels faulty, and still working at some gain setting, I would suspect something like a supply or control signal (e.g. some HC4094 or HC595 chip or a small DAC to control VCAs) to the variable gain part.

What happens with the non working gain setting ?  There is a difference between always reading zero, just not signal but still Y-pos working and just a wrong possibly way to small or or large amplitude. 

[NEELIMAVUNGAL]

With both channels faulty, and still working at some gain setting, I would suspect something like a supply or control signal (e.g. some HC4094 or HC595 chip or a small DAC to control VCAs) to the variable gain part.

What happens with the non working gain setting ?  There is a difference between always reading zero, just not signal but still Y-pos working and just a wrong possibly way to small or or large amplitude.

Thank you, please see this video https://youtu.be/KqNTTcAdRTM and ask me for further clarification of the status.