Audio amplifier - dc on outputs (stk4913)

Thread Starter

Sameerasl12

Joined Jan 10, 2020
2
Hello Guys..

Im trying to fix an audio amplifier (stk
but im not sure about the trouble shooting process.

I've measured 35V DC on both channels.

Any suggestions on where to go from here would be appreciated.
 

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MisterBill2

Joined Jan 23, 2018
4,855
First, verify that the voltage is actually present on the supply voltage pins of the module. Then check that none of the cheap aluminum electrolytic capacitors have become leaky. Because the entire module is DC coupled, a small DC offset at the input will cause a large offset such as what you are seeing. So the very first thing is to verify that the input is correct, and very close to zero volts. The device is a module, NOT an IC, but still not repairable. I once helped a tech repair a similar unit, and the failure was upstream of the expensive STK module. Thus you need to first verify the upstream circuit. The input DC level is very important.
 

Wolframore

Joined Jan 21, 2019
1,533
This is what they call the datasheet calls “thick film integrated circuit”... it’s not repairable
171792C8-7AF4-4AA0-ABB0-C9F30971A9F8.jpeg

There are two opamps with the outputs at the center..those are some interesting looking and large output transistors.

0138D3C0-239C-4117-95AE-2F9E10E92B56.jpeg
 
Last edited:

Tonyr1084

Joined Sep 24, 2015
4,035
Seen that amp before. Mine is an STK4192, 50 watt per channel, 2 channel chip. Out of an OLD Sanyo stereo. I have even older amps laying around that have been scrapped for parts.
 

Ylli

Joined Nov 13, 2015
877
I repaired a receiver that had a bad RSN module. Similar to the STK's. Only place I could find one was China, so went ahead and ordered. New one was worse than the original. Vendor was willing to send me a different one, but wanted me to document destroying the first one before he would send the second. Second one did work.
20190610_110054.jpg20190610_110210.jpg20190610_110354.jpg20190610_110520.jpg20190610_111435.jpg
 

MisterBill2

Joined Jan 23, 2018
4,855
Once again, I suggest first being certain that the signal input voltage is correct, and also that the external bypass capacitors are all OK. Sanyo stuff of that vintage is totally DC coupled, so a failed input component can cause a lot of output problems. AND, while I do not have the equipment to repair that module, other folks do.
For a replacement device, check with the ECG company. They are honest, at least.
 
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