Thanks coromonadalix.
I swear no GMC DMM's were hurt during that project
The amplifiers these are used in still sell for into the 100-150€ range, in contrast non working ones sell between 30 and 60€.
The last amplifiers I've repaired were equipped with two of my clones so that left me with an original STK to sell separately (about 30€).
It seems a shame that people should trash these amplifiers because of the STK hybrids, they're not that bad when working.
I suppose that all the people aware of the problem sell them for parts or trash them, the less aware buy a Chinese STK then trash them.
I think I missed the right time to tackle this, even 10 years ago I'm sure there would have been plenty more demand.
I also think it is more important to a lot of audio people that the replacement component looks like the original and bears "new class A" although electrically rubbish rather than being electrically identical but looking less inspiring.
Audio is all about blue lights salesman's jargon and aesthetics.
I'm only looking to recover my time and component investment on this, after I'll be pleased to share the Gerber's with whoever wants to save their amp. or (more likely) make money on my back.
Edit:
I have an ad. up on eBay, a little expensive maybe, I'm going to remove it anyway, now I've been through most of the latest downsides to eBay it just isn't worth doing business with them.
The biggest deception being that to transfer money from eBay sales to my bank account I must give them the right to draw money from my bank account when they decide. To hell with that.