Post by geoffPost by p***@hotmail.comA bit late for a reply now but you never know. I was Studiomaster's
Senior Design Engineer then and specified the transformer. It was
made by Toroid International, now part of NORATEL, who kept the red
hedgehog trademark that originated with the former company
Transduktor.
I did have a bunch of ones scavenged from blown Studiomaster amps and
mixer-amps. However a few years ago I decided there was no use for
them so they went to the scrap merchant.
geoff
PS - what was it that caused all those amps to vapourise (PCB tracks and
semiconductors. The theory here was that the factory in India was using
counterfeit components....
That hopeless factory in India (you wouldn't believe what shenanigans they got up to that we discovered) did indeed used some counterfeit components in the output stage. We spotted the problem in the UK too. Sawing the lid off the TO-3 can, there were 2 small chips wired in parallel. The transistors were marked as made by MOSPEC, which is indeed a genuine semiconductor company, second sourcing various devices. Their data sheets for the MJ 15003 & 15004 were basically photocopies of the original Motorola ones. I suspect the counterfeiters chose MOSPEC to 'copy' as they were less well known.
Aside from that, the Studiomaster BOM *explicitly* stated that Motorola/On-Semi parts were to be used ONLY, so they were deliberately cutting corners. We insisted that they throw away the remainder of the batch or negotiate a refund from their supplier.
On top of this, I was for ages puzzled why the full power THD of the 350W amp module rose from 0,007% @ 1kHz (utterly reproducible) to 0.01% when transferred to India. It finally turned out that they were using 1/2 oz (17 um) copper clad pcb's ! Hardly any surprise about vapourising tracks.
I'm only touching the surface of what they got up to. Basically, they destroyed Studiomaster's good name. In the end they also withdrew credit facilities and that version of Studiomaster had to cease trading. I recall the Managing Director bemoaning the fact that he'd lost a million pounds, yet is was *his* idea to transfer all production to India because Prosound's MD made himself out to be a 'mate' of his.
In one of his more lucid moments, our 'R&D Manager' apparently overheard Prosound's M.D. stating that he would one day 'own' Studiomaster. He did indeed continue to use our name and manufacture our products for other companies and even introduced crap new products like radio mics designed for classic 'P.A.' use that were hopeless under the Studiomaster name in the Indian market. We actually got an enquiry about one of those mics in the UK and had to tell the owner that it was nothing to do with us.
There's plenty more I could tell, I assure you. I'm rarely roused to anger but Prosound's Manufacturing Manager got a full-on dressing down from me once after Borje from Toroid and I met up in Mumbai to look at a transformer issue ourselves. We asked for an amplifier to be set up in a certain way with a variac etc. On return from lunch, NOTHING had been done at all. Borje even swore under his breath, threatened to stop supplying Prosound and I gave the manager a good yelling at. This is something that clearly normally doesn't happen in India, since when I was finished and shaking with anger, I noticed that the entire R&D - lol - staff were standing still as if stunned with their mouths open.
Moral of this story, DON'T outsource when those making the decisions don't know what they're doing, as was the case here. In comparison, we found both excellent and slightly dodgy (the one that make some Yamaha stuff) companies in China.
Graham
