Guyatone PS-002 chorus with hissing noise

[spleenharvester]

This pedal came to me in a job lot about 15 years ago I bought for £20 (which included an Able Bassmaker, a DS-1, a GCB-95 and an EQ pedal, probably the most ridiculous haul I've gotten to date). I forgot it existed until it fell into my lap again today after my parents had a clearout.

It sounds absolutely amazing, but there's quite a bit of background noise/hissing when AC is plugged in and the effect is on. On 9V only there's no hissing. I haven't tested a different AC adapter, but that AC adapter doesn't cause any hissing when plugged into any other pedal, which makes me think it's the PS-002 (that and it's about 40 years old).

I've bought some replacement electrolytics to do a complete recap, would appreciate any other ideas.

Gut shots:

 

[Mincer]

I'd think the easiest is to try another adapter. Sometimes older pedals can be pretty touchy with different adapters, even if they are rated properly.

 

[spleenharvester]

Ah ok, will give that a try. I did pull a couple of caps off the board and they are reading nowhere near what they should be, so I think it's probably worth a recap anyway.

 

[spleenharvester]

So I've found a thread over at DIYStompBoxes where someone has the exact same issue and has posted a schematic, including a video which is an identical noise to mine. (Annoyingly I can't seem to register so I can't ask them themselves). OP there couldn't solve it.

Now that I've pulled the caps off they seem to read OK, the 1uF caps are about 30% higher than they should be but nothing major. Not really sure where to proceed from here, going to recap anyway as I've already ordered them but I think it's unlikely to help.

Have ordered a Boss BCB-60 board + PSU anyway so can rule that out soon.