Boss OS-2 problem - please help!

[Fuzz Lumpkins]

Please check this out:

The problem, as the video demonstrates, is that the sound rather randomly cuts out completely and sometimes drops in volume. Giving it anything from a slight tap to a few moderate bangs fixes the problem... but it also causes the problem; i.e. the pedal's working fine, has a light nudge and cuts out. There are other times when banging and shaking the pedal causes no problems whatsoever.

I've had the Boss OS-2 for approx. 17-18 years and as far back as I can recall I've had this problem, which is why I've only recently picked it up again.

I recently opened it up and took everything out of the pedal casing to check the input and output jacks, and I couldn't SEE any problem (e.g. bad soldering, loose wires or rust).

However, while in this state I connected the pedal to a 9v battery to test the unit and there was no sound except for a loud hum. I suspected this may be due to it being out of its metal casing - although I have no idea why/how this would affect anything - so I put it back inside the casing and it's back to its usual self; i.e. sometimes a bump causes the sound to cut out and it needs another bump or three to return to normal.

Anyway... What I want to know is if anyone knows: 1) what's causing the problem; and 2) how I can fix it.

I'm relatively inexperienced with electronics (e.g. I've diagnosed and fixed a laptop screen problem by replacing the backlight, so I can follow basic instructions) but I'd rather try to fix it myself before contacting an expert.

Thanks in advance for any help you can provide.

[jmaf]

You can look again, tap the inner parts using something pointy, you'll find a broken/breaking lead, loose jacks, cold solder, etc. It's sometimes hard to find, but that's likely a mechanical problem. If the opamp is in a socket, push it again into it, maybe it's a bit loose.

Edit: Bat potentiometers are most likely in these cases. Tap their head one at a time instead of bumping the entire pedal.