Do you have any advice on diagnosing where the grounding issue could be? Should I try soldering the mounting screws? Is there a couple of test points I could probe to see if there's a short happening?
Wouldn't suspect the screws, unless some of them are actually missing or loose. What I would do is test the unit with case removed (and that copper foil desoldered) to see if it makes any difference. Would also replace the 2 output caps.
After a bunch of testing (I still don't have the replacement caps) I have figured out that the click is massively reduced if I hold the board up off the posts and away from the moving gears. To the point that if a tape were playing I almost certainly wouldn't hear it. Holding the board and touching the metal frame also reduces it some. Trying to isolate the mounting posts (with some cloth tape) and resting the board where it would normally go doesn't change anything. I've tried holding just the wires away while the board is in place but that doesn't change anything either. I'm not really sure what to do with this information but I'm going to keep trying to isolate things one by one till I find the culprit of the grounding issue/short/whatever it is. And replace the caps once I get them, but with this info I'm thinking there's another issue to be solved as well.
That's interesting. There are a couple more things that can be checked: - desolder the motor (red and white wires) and see if the pops still appear without motor being connected. - check C305, if it's broken and properly soldered. - check the shield of the head cable, that it's actually connected to circuit ground.
It's not the motor hum: Before taking the motor off and desoldering it I decided to run it with just the drive belt off and there is no click. Not even reduced click like before, straight up zero click. So that makes me think the magnetic clutch is screwing with something that's not shielded right or not grounded right. The ground on the head cable is soldered to the ground pad correctly and I tested that there's no broken connection between. I'm not sure where C305 is as the circuit diagram in the service manual on walkman.land is different from my unit slightly (I have a later model I guess).
Would using cloth first aid tape to hold wires down cause static build up? Because I removed that stuff and swapped it for ESD tape and the problem has gone away for 5 days so far...
The glue used on the tape very well can accumulate static build up. Haven't seen it since I've never used this kind of tape when restoring walkmans, but I think it is possible. So it's probably a good idea to use electrical tape to hold the wires. Glad you found the problem in the end !
