How to test STK ICs?

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I just parted out a Technics SA-300 that was putting out 40 volts on each channel. Does that mean that the STK packs (STK0039) are likely to both be bad? How would I go about testing them? I have a multimeter but no advanced equipment. Thank you!
 
If you can find the pinout, you might be able to get across the output devices themselves and do a basic continuity check. Sounds like its shorted. If so, a multimeter on the diode check function will give enough of a pass/fail for this purpose.

stk0039-stk0059.jpg


Looks like checking 8 to 9 and 2 to 3 will give you emitter and collector, and thats where I'd expect to see the short if its there.
 
to be sure check pin 2 and 9 voltages and check the 0.33 emitter resistors .
edit ..bit late for that .i should have read the full question ..
just check for shorts first .
 
STKs are very prone to dying, so if a STK ridden amp is misbehaving, it's usually said STK. And whenever a STK is dead, all you can do - as you have correctly done - is part the unit out. No original STKs are available any more*, since most were discontinued in the 80's. Obviously you cannot find 40 year old parts any more.

Fakes are abundant and very dangerous. Giving them a chance means two things: 1. You'll waste your money. 2. You'll waste your time. In the end, you'll be sitting with an even deader amp than before.

* Modern STKs are still being used and in production, I am strictly talking about old gear here.
 
I don't completely subscribe to the counterfeit rumors. Many parts of the world retain their equipment and repair it when it fails. There is a demand for good repair parts to keep the non-disposable part of the world running. Equipment is expensive in third world country's, so repairing the stuff we deem junk they make profit in. The STK's we see here are made for that demand. The main things to watch out for in repairing the module driven sets is find a seller with history in selling the modules. Second make sure the amps driver stages are solid and fault free before installing any STK device. Third, prepare the module and heatsink for mounting by trimming back the plastic edge of the module allowing the metal back of the module to meet with the heatsink (This is Key) as any output transistor would. The modules get HOT! even when running at low/min volume. It is imperative to have good thermal contact to the heatsink. I've repaired many module driven sets and have only success with all of them. A few had driver stage issues that needed to be corrected others just modules. The counterfeit rap - I believe, comes from novice repairs.
 
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I bought out a repair shop years ago and still have a fair selection of NOS STK modules so they do still exist it's just a little tricky finding the real deal.
 
Technics SA-300 that was putting out 40 volts on each channel. Does that mean that the STK packs (STK0039) are likely to both be bad?

I'll admit I know nothing about the Technics or the STK0039. But, are those IC's designed to be capacitive coupled to the speakers?

If so, did you see that voltage with them "open ended"? Or, did you have some resistance on them?
 
I don't completely subscribe to the counterfeit rumors. Many parts of the world retain their equipment and repair it when it fails. There is a demand for good repair parts to keep the non-disposable part of the world running. Equipment is expensive in third world country's, so repairing the stuff we deem junk they make profit in. The STK's we see here are made for that demand. The main things to watch out for in repairing the module driven sets is find a seller with history in selling the modules. Second make sure the amps driver stages are solid and fault free before installing any STK device. Third, prepare the module and heatsink for mounting by trimming back the plastic edge of the module allowing the metal back of the module to meet with the heatsink (This is Key) as any output transistor would. The modules get HOT! even when running at low/min volume. It is imperative to have good thermal contact to the heatsink. I've repaired many module driven sets and have only success with all of them. A few had driver stage issues that needed to be corrected others just modules. The counterfeit rap - I believe, comes from novice repairs.

I second this, I have had a great result with a so called fake and totally agree that if it blows up you didn't find the original fault.
 
I recently bought a SP-40w off ebay and an STK0050ii. The 50ii worked fine but the SP-40w was a dud but it definitely looked genuinely second hand (see the pic). I have doubts the ebay sellers are making fakes then making them look second hand, all for a few bucks a pop. And if they were manufacturing them from scratch, why not make them work 100% (or at least 99%) and sell them for a decent amount with a warranty? My guess is they come out of the vast electronics recycling industry in China and other countries with cheap labor - the Economist says 10000 people work in this industry in China alone and the electronics originate from countries like the US and Japan so plenty of opportunities for broken stereos to enter the system. However, testing the parts is expensive so my guess is they sell them cheap and accept that most are duds. recycling.jpg recycling2.jpg sp40w.jpg
 
That was my understanding too. However, Dwayne Heath wrote he "was about to get them" not "make them" which is what had me wondering.
 
That was my understanding too. However, Dwayne Heath wrote he "was about to get them" not "make them" which is what had me wondering.
I meant I was gonna get a pair and build them..lol..but how come no one is building them and selling them assembled
 
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