STK465 replacement.

[Mike Cole]

I am a very experience tech, and am having a lot of trouble replacing a blown STK465 in a Yamaha Organ. I am now on my 5th chip, The problem is on install the chip puts out -24 to -28 volts dc on its output leads, and therefore the dc protect relay will not pull in. I have replaced all the small electrolytic caps on this subassembly, and checked all the resistors, out of circuit. At one point I suspected sub-par / counterfeit chips so I ordered and replaced with a genuine Yamaha replacement STK465, with the exact same results. I have checked almost everything I can, and am ready to tear my hair out! Anybody have any helpful advice?

 

[Martaine2005]

Hi, you have probably seen this but it seems very informative.
http://www.petervis.com/electronics/stk465/stk465.html