How to test a STK0060?

[Frank3]

I am a bit of a noob on this but learning quickly. I have a JVC SA-55 that blows a fuse on power on. I remember it doing this 40 years ago when I pushed it too hard. Back then it was the STK0060 module shorted and repaired under warranty.

To today. I removed the STK0060 pair and tested power again and fuse did not blow so I think I have at least found the short.

My question is that after reading the STK0060 datasheet I am trying to use a multimeter to confirm the short or bad part. Any suggestions on how to properly test? Looks like 1,2,3 and 8,9,0 are the pins used and 2,3 and 8,9 look like collector and emitter on the diagram. 1 and 0 are base. 1,2,3 deal with positive voltage and 8,9,0 deal with negative.

I know based on research these power packs are a real can of worms but I am trying to learn more about proving one faulty with a meter if possible. That way I can test a couple of the newer modules, the ones cited as fake, to try to bring this to life. Failing that I may have to learn more on how to do the neat build I saw in the STK0050 thread with discrete parts and an aluminum heat sink.

I blew this thing over-driving 4 ohm speakers, my bad. So I want to fix it and retire it to lighter duty 8 ohm loads.

Going to use my Hafler DH200 to drive the 4 ohm stuff.....

Thx,
Frank

 

[rcs16]

You basically have two Darlington connected npn and pnp in a push-pull arrangement, so you can do some DMM measurements in diode test mode with power off of course.
Pins 8-10 are for the npn, put your + on pin 10 and - on pin8 reverse them for the other side, should read two Vbe or two diode voltage drops.
You can also measure the Vbe multiplier if bias generator the same way.
The true test is applying power and measuring bias current, passing a signal through in a test setup where you need a front end. I use the front end of an amplifier for this task

 

[gadget73]

pretty much how I've tested them as well. If there is a short at the output pair you'll find it pretty fast. Can't really fully test it out of circuit but fair guess if the output pair passes the basic diode checks, the rest isn't super likely to be fried.

I did once have what I thought was a shorted STK, but it was a small transistor feeding the input of the STK. The clue that I missed was the voltage at the speaker outputs was a couple junction drops lower than the rail voltage.