EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on November 16, 2018, 01:11:12 am
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:-BROKE
https://www.youtube.com/watch?v=OBOgiMA89Ks (https://www.youtube.com/watch?v=OBOgiMA89Ks)
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Dave, just connect your serial cable to the scope. You'll see more ;)
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I wonder if there is a bad relay or solder joint that is common. Perhaps the calibration source? Probably no hope of finding schematics.
I see a teardown and repair video in your future for this scope.
Sam
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(https://i.imgur.com/2G7JVWV.png)
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You didn't leave any of the hack links set did you ?
ISTR that offsets were one thing that made the apparent bandwidth increase hack not actually useful
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I don't think that the calibration signal is what it should be. It is all over the place, so no wonder the poor thing gives up.
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The calibration traces do not look that bad, in scopes that are functioning they jump all over as well, it is part of the calibration algorithm.
Try removing the CPU/ASIC board, cleaning the contacts and re-installing it.
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although when it moves around slowly it looks exactly like what happened to us on a batch of boards..
There was this issue where a PWM signal was filtered with a two pole Sallen Key and the guy who drew the schematic forgot to put the capacitor between the positive input of the opamp and ground on one channel.
It was ridiculous! the schematic was thight, if he had just copied the filter from another channel the infamous capacitor would have been on the title block, so he must have removed it never to add it back again :palm:
Anyway, the issue was that besides worse filtering of the signal there was a heavily distorted oscillation when the duty cycle changed between zero and about 20%, of the same kind i saw on the video. I would inspect the calibration signal circuit to see if there are cracked caps or something. every time i did self calibration i never saw a signal like that
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That was a throwback. It reminded me of the well worn out analog oscilloscopes of the university labs, where the amplitude level switches made the GND level jump around like a crazy monkey! The potentiometers and tappings on the front panel caused all sorts of glitches on the waveform. :-DD
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I'm curious as to what the calibration logs have to say as to what went wrong. Using my Windows CE desktop hack (https://ripitapart.com/2018/10/15/gaining-access-to-the-windows-ce-desktop-and-doom-on-the-keysight-dsox1102g-oscilloscope/) I found that there are some .txt files (\Secure\cal\UserCal8Log.txt, \Secure\cal\callog.txt) and they provide some pretty verbose information as to the tests it performs, how long each test took, and so on.
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A lot of good ideas here, but we have to really see the serial log under the calibration process to see what's going on. ginbot mentioned the UserCal8Log.txt It's a copy of the serial log and you can access it without opening your scope, but probably your scope is already open :-DD
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Was the cause of the issue ever determined?
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Was the cause of the issue ever determined?
It was the hack:
https://www.youtube.com/watch?v=xbqx25wT2Qo (https://www.youtube.com/watch?v=xbqx25wT2Qo)