I looked at the other jbl's on hifiengine for a service manual, but didn't see one close to this model. Do you happen to remember the model #? Thanks!
Simple idea:
Check the continuity from heads to circuit board.
Then, playing a cassette, use a headphone as a probe, or an amplifier, the ground of head connected to shield, and central pin as probe.
Use a capacitor to filter DC.
You should hear audio, and trace the path, unless it is a digital type set, which I doubt.
That should be enough to find the fault, which could be a faulty switch, broken wire, or an electronic part failure.
Check the continuity from heads to circuit board.
Then, playing a cassette, use a headphone as a probe, or an amplifier, the ground of head connected to shield, and central pin as probe.
Use a capacitor to filter DC.
You should hear audio, and trace the path, unless it is a digital type set, which I doubt.
That should be enough to find the fault, which could be a faulty switch, broken wire, or an electronic part failure.
Sorry. Been super busy. Got back at it to day.
So...with power ON , but nothing playing, I measured the 4 "VR" trim pots (each) for both transports. I've attached a picture. I measured each of the 3 solder points for each VR. I get roughly 3.5v at two spots on transport B, but I say "roughly" because as soon as I start to measure, the voltage starts dropping. I also get roughly 2v at one spot, but it too starts to drop when I measure. All the other solder points for all 4 pots show 0v
Moving on to transport A, I measured each of the 3 solder points for each pot (VR). You can see the two points where I get just under 1v, and it drops quickly. All others show 0v.
Does that shed any light on anything? That white residue you see is just where I had cleaned with IPA after reflowing a bunch of solder points.
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Right. I understand. Before I did that I just thought I'd measure the idle voltages at those pots