Electronics > Repair
BK Precision 2120 trace issues
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vexatag:
Update: the resistors came in and I figured out the problem with my soldering (cheapo 63/37 solder doesn't leave a nice shiny joint ;__;), now I have the casing off but I don't know how to proceed with removing the pcb in question. Is there a "best" order for removing the connectors? How do I disconnect the switches from the front face?
bdunham7:

--- Quote from: vexatag on July 22, 2020, 11:31:47 pm ---Update: the resistors came in and I figured out the problem with my soldering (cheapo 63/37 solder doesn't leave a nice shiny joint ;__;), now I have the casing off but I don't know how to proceed with removing the pcb in question. Is there a "best" order for removing the connectors? How do I disconnect the switches from the front face?

--- End quote ---

Fake solder seems to be a thing now too.  I have some that came 'free' with some junk or another and it is like stirring mud.  As far as disassembly, take pictures for putting it back together, post them if you want.  I don't remember how the knobs and switches came off and the one I fixed was a little different than yours.  It can be tricky.  Can you do it without disassembling the front?
vexatag:
Practically speaking, no. Between needing to desolder and solder the resistors from a very small vantage point without damaging any other components and the cleanup of the fresh component leads, it's a bit beyond my comfort zone. The square buttons are easy to remove however (pull on the metal shaft) and I know I somehow got the x position knob removed from the pot by accident, so it does seem possible.
vexatag:
Ok, swapped the resistors out. TP260V is reading 265.5v, however the trace is still just a point. The trace is also even further to the left, I can get it about 1.5 cm away from the left edge in either X-Y mode or in x10 mode.
bdunham7:
That's too bad--it was looking hopeful for a bit once you found those bad resistors.

So if you feed a signal (perhaps the probe calibrator) into the X-channel (in XY mode) can you get at least a small horizontal line that varies with the input voltage range setting?  And if you feed the same signal into the Y channel, can you get a vertical signal at all?  What else do you have that you can use to input a signal?

If you get a vertical signal at all and the X-axis responds even slightly, my first guess is that your next problem is within the horizontal final amp circuit.  You can start testing that circuit by verifying the +24 and +12V points are correct, and then depowering and measuring all of the resistors, starting with everything to the right of Q807.  Remember, high resistance = broken, low resistance = needs further thought.

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