| Electronics > Repair |
| BK Precision 2120 trace issues |
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| bdunham7:
The voltmeter modules draw their power from the circuit and the 10K pot can't supply much current. They aren't a good idea for this application. So on those tests, what ranges of voltages did you see on the input side and on the trigger level side? You should do this again and make a chart showing what the input voltage side measure at with the pot all the way up, 75%, 50% and so on. Then do the same for the trigger level pot. You will need to be able to set certain voltages without too much measuring because the next step will be to send those voltages to the comparator U601 and observe its output. |
| vexatag:
The changes were very brief unfortunately, generally ranging between 1.25 V and ~3 V. I don't think I saw anything higher than 5.5 V. Of course, it might have just been noise since it also settled down to 0 V. This definitely seems like the sort of situation where another scope would be useful, is it time to try using a soundcard scope? |
| bdunham7:
The one on the trigger level side should be steady. The other one, I think, should also be steady if the coupling is set to TV-V/DC, but let me review the schematic. Are you saying they both settle down to 0 volts no matter where you put them? Yes, we are getting to the point where another scope would be extremely useful. I don't want you to damage your computer, but I suppose as long as you used high value resistors for the input maybe it works. Do you have soundcard scope software and an adapter cable? Your sig-gen might be useful too, but the output is low. |
| vexatag:
I'm not actually sure which side is which, but both sides settle at 0 V when changing the pot on the battery pack, one side settles at 0 V with minimum trigger level and 0.031 V at maximum trigger level, the other side settles at 0 V with minimum trigger and 0.015 V with maximum trigger. --- Quote from: bdunham7 on August 05, 2020, 12:24:32 am ---Do you have soundcard scope software and an adapter cable? --- End quote --- I've got both of those things, it's somewhat janky because I bought the wrong connectors but seems better than nothing. |
| bdunham7:
OK, why don't you see if you can get your soundcard scope to work with your signal generator and show some waveforms. Then you can try feeding them in to see if you can trip the comparator. I don't actually think the problem is in this area, but it needs to be confirmed before moving on to the trigger logic circuit. Use a resistor on the input of the soundcard scope, I'd recommend at least 10K, to minimize the possibility of computer damage. |
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