Longshot, but you could try contacting this guy/seller in AZ (seen him post @ headphone sites and it looks like he’s still active).
https://www.usaudiomart.com/details/649634003-melos-sha-gold-full-recap-tortuga-ldr-volume/
haha i was the one who bought that cool modded unit from ricky in az
i too have fond memories of the melos units from back in the day... simple circuit, great transparency and tubey goodness that can be tuned via the tube choice
he is not really in the business of fixing those melos sha units... but he certainly knows his way around them!