Whinig sound with Washburn Soloist Distortion

[Mann]

I bought a Washburn Soloist Distortion knowing it was not functioning properly. When I tested it, it worked but with pots turned fully clockwise it produces a whining sound.
Any idea where to start repairing? (I bought it actually for the enclosure but if there is a way...)

[Mark Hammer]

How fresh is the battery?  I've built a bunch of things over the years that, as the battery starts to drop significantly, will work "fine" at lower gain/volume levels, but start to oscillate when either gain or output are increased beyond halfway or so.  I've never understood it, but it is a replicable phenomenon.

Of course what makes this so odd is that there are other pedals which people feel sound better when the battery is low and dying.

Ain't life strange?

[Mann]

I use 1spot and I knew about the whining and I paid practically nothing of the pedal. There two small surface-mounted pcbs so I don't think that I'm going to find the fault. I'll check the pots and that's it.
Thank you for answering.