Electronics > Repair
BK Precision 2120 trace issues
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vexatag:
I've also got an eight-AA holder if that'd maybe work better? The only 9v clip I have to sacrifice is on the 1khz signal generator and I'd hate to sacrifice it.
bdunham7:
Yes that should work.  10 x 1.5V =12V.  12V thru 10K pot = 1.2mA, 14.4mW dissipation.  But you need 8 AA cells, I suppose the Sunbeam ones from a dollar store will work.

Tell me more about this signal generator, like output specs and so forth.  It might be handy.
vexatag:
The holder actually has eight rechargeable AAs in it, I've been using it to power a 140mm PC fan I've been using to extract rosin fumes when soldering. It has a standard 5.5mm DC barrel jack, so hooking it to the pot should be easy enough. (and yes, I've got 5.5mm barrel jacks for the receiving end, I purchased a twenty pack with ten of each for an earlier project)

The signal generator is a Velleman MK105, I believe I mentioned it earlier in the thread as one of my resources.

EDIT: I hooked the positive line to pin 1 and the negative line to pin 3, next I hook up a wire connecting pin 2 to pin 3?
bdunham7:
Your output wires will be pin 2 (+) and pin 3 (-).  Try it on a voltmeter.
vexatag:
I totally misunderstood how potentiometers work, whoops. The only thing I added was component leads on 2 and 3 to give my garbage scope probes something to hook onto.


--- Quote from: bdunham7 on August 02, 2020, 03:56:15 pm ---Next, [...] right where you found the AC signal on S603.  If everything works, you should be able to turn  your pot up and down and see the voltage change in sync at the center input terminal of S603.

[...] By 'opposite', I mean in the other row--there's two rows of 4 or 5 terminals, same postion/opposite row.  Then, with the scope turned on and the trigger level knob not it AUTO (pulled out), you should be able to turn it up and down and see a similar change in voltage at that point.  These are the inputs to U601 (or U615??) which is the trigger comparator--it turns on when the voltage on the input side exceeds the voltage on the trigger level side--or vice versa if SLOPE (-) is selected. 

--- End quote ---

I did the tests you asked me to and was able to get AC voltage changes on both pins.

Side note, I did find four three digit voltmeter modules from a previous project (rated at 2.6-30V according to the packaging), so that's a cool thing (or would be if they cooperated with the 10k pot, I hooked one up to pin 2 and 3 but it didn't respond correctly, the display dimmed at 2.35 v with the pot mostly closed but cut out at 3.5 with the pot mostly open. It's something I'll need to look at further later I think).
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