Atten ADS1152CA trace issue - Page 1
Forum section: electronics / repair

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 21, 2019, 01:46:15 pm
content: 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

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 23, 2019, 06:30:16 pm
content: 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

author: tautech
author_rank: Super Contributor
timestamp: October 23, 2019, 08:09:29 pm
content: Try Default.Then press V pos for each channel so to zero their positions.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 24, 2019, 12:26:11 am
content: Quote from: tautech on October 23, 2019, 08:09:29 pmthank you for the comment. I have already tried even factory default. the result is same.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 24, 2019, 03:22:08 am
content: I think this is a hardware issue. if so, what could be the problem,

author: Microcheap
author_rank: Frequent Contributor
timestamp: October 24, 2019, 04:16:06 am
content: 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.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 24, 2019, 07:05:50 am
content: Quote from: Microcheap on October 24, 2019, 04:16:06 amThank 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.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 24, 2019, 07:16:31 am
content: 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.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 24, 2019, 08:16:59 am
content: Look at the voltages. is this normal

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 25, 2019, 03:13:10 pm
content: Hello all, please see the picture what is that marked chip 6552. Is that op amp or mosfet. please help.

author: mikerj
author_rank: Super Contributor
timestamp: October 25, 2019, 07:37:02 pm
content: Possibly anLMH6552, a high bandwidth differential amplifier.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 25, 2019, 10:32:44 pm
content: 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.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 26, 2019, 01:00:43 am
content: Quote from: mikerj on October 25, 2019, 07:37:02 pmThanks, let me try to find out.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 26, 2019, 01:03:15 am
content: Quote from: Kleinstein on October 25, 2019, 10:32:44 pmthanks for the replay, It is not only a trace positioning issue, but I can not trace except in 500 mv division on both channels!

author: tautech
author_rank: Super Contributor
timestamp: October 26, 2019, 01:12:02 am
content: Quote from: NEELIMAVUNGAL on October 26, 2019, 01:03:15 amAh, 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 ?

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 26, 2019, 04:31:38 am
content: Quote from: tautech on October 26, 2019, 01:12:02 amyes, 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 26, 2019, 07:42:04 am
content: 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.

author: NEELIMAVUNGAL
author_rank: Contributor
timestamp: October 26, 2019, 11:37:58 am
content: Quote from: Kleinstein on October 26, 2019, 07:42:04 amThank you, please see this videohttps://youtu.be/KqNTTcAdRTMand ask me for further clarification of the status.