I'm having electrical issues with my Model F107 and I need some help.

[Steveenn]

I've had the same issue with my Model F107 since I got it and restored it back in November. As far as I can tell, it's a grounding/shorting issue between the plates and the PCB. The case is metal, and due to the way the board is held together, it is in direct contact with both the top and bottom plates of the inner assembly.

The problem I'm having is it's sending keystrokes in when I touch the case, and the more skin I have in contact with the case, the more characters it spams. So that makes my think it's a grounding issue, and the more resistance I give the case, the more characters it spams. It starts with a few keys on the numpad with just a light touch with one finger, but if I touch the case with my full two hands it spams every single key on the board as fast as Windows will register them. I've had Windows crash before because of so many keystrokes coming in all at once.

[pr0ximity]

Have you disassembled the board entirely, separating the plates and foam?

I would do that, ensure the PCB is clean, and check the state of the insulating sheet between the PCB and bottom-half of the case.

I'm usually pretty terrible with all things electricity, but I think you could use a multimeter to see if the case is indeed not grounded. Check potential between the case and a known ground (PC case)?

Basically worth checking if it is indeed a grounding issue or merely the pressure on the case. Though you did say it was with only a light touch, anything's possible with a capacitive PCB and small movements.

[Steveenn]

When I restored the board in November everything was is perfect working order, and during the process I replaced the foam with some 2mm craft foam as most of the guides I have found said I should. It didn't start acting up until a good while after I restored it, I'd say at least a month or two. When I took it apart earlier today I noticed that the paint on the top plate had been worn through in a couple of places, which is giving it the direct contact to the case, and by extension my fingers. I put down some electrical tape covering the scratched areas, but it really hasn't helped at all, as the problem still persists. As far as I can tell, it's caused by the clamping force the case puts on the inner assembly pinching the plates closer together when screwed together. It doesn't happen while I have the inner assembly outside of the case, only when I put it in the case. I really don't want to open up the inner assembly again as the locking tab has gotten rather brittle and I don't think it would hold up to me bending it open again.

[fohat.digs]

As far as I can tell, it's caused by the clamping force the case puts on the inner assembly pinching the plates closer together when screwed together. It doesn't happen while I have the inner assembly outside of the case, only when I put it in the case.

There is a rubbery spray-paint-like insulation that perhaps you could coat the entire insides of the case.

Since the entire case is metal and all of the pieces are screwed together, it seems to me that they could hardly be isolated from each other anyway. I use rubber washers quite a bit just for sound reasons, maybe that could help.

But I am no electrician and don't know much about capacitance and grounding.

[Steveenn]

I tried to isolate everything I could, I put electrical tape on all of the contact areas and it still causes problems. As far as I can tell, it's something in the inner assembly that with enough pressure it causes a short to either the top or bottom plate. I can squeeze the inner assembly with my fingers and it has the same effect since the far sides of the case does the same thing when I tighten down the case screws.