I used brutal force to open STK082G hybrid module from old DUAL amp. Most people, including me, presume that defunct module is due to fail output transistors but it seems to me that output transistors are OK, nothing seems fried. But there is one SMD component, I am not sure if it's resistor or cap, that seems like the color of body is spilled around the component.
I am so sorry to see such advanced component to be discarded just because SMD component failed, if that's the reason. After all discrete components could easily be serviced, but if you have to throw away complete power amplifier just because one SMD component... Hybrid modules looked like such smart idea...And they sound very good too...
I am so sorry to see such advanced component to be discarded just because SMD component failed, if that's the reason. After all discrete components could easily be serviced, but if you have to throw away complete power amplifier just because one SMD component... Hybrid modules looked like such smart idea...And they sound very good too...
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unfortunately the audio manufacturer themselves didn't respect the datasheet prescription for those transistors.
No, it's not melted . It's consequence of my hammer hitting at the middle of the case. I had to hit it real hard to open it. It appears flat because of the pressure.
In the image from your first post, I'm pretty convinced that the lower output transistor is shorted. If you look at the 2nd notched area inside the transistor, looking from the inside out, you will notice that the area of the lower transistor is dark gray, while the same area of the upper transistor is light gray - this is a sure sign that the transistor is shorted. Btw, I used a little more elaborate method to reach that conclusion with STK power modules, light hammer, scalpel and watch screwdrivers, so I managed to save the output transistors bonding wires so I could test them on a curve tracer.
That's a ceramic decoupling capacitor, the colour is a dead giveaway, it's very unlikely that there's any problem with it. The discolouration around it is flux.
May be that output transistors fail because there is no emitter resistors? It's a pity that STK modules expire at some point. They sound very good. I am sorry that they are not available anymore. STK082G was excellent quasi amp module.
Hmm...I have to correct myself, the above statement is incorrect. I looked again (under the magnifier) the output transistors of the STK modules I have (complementary output), and one thing is for sure, the 2nd toothed surface inside the NPN transistor is larger than that of the PNP transistors and both are completely black in color under a certain angle of view and light.
In any case, you can still see if the transistor is shorted, use a diode measurement on DVM, the transistor base is the edge surface of the crystal, the transistor emitter is the surface in the middle of the crystal, the transistor collector is a large square surface.
There is still hope for your amplifier, because I found that some of the fake STK0100II power modules (housing and pin number correspond to STK084) I received from Chinese sellers, are most likely the original STK084 or STK084G because they did not bother enough to remove the existing code (84BC096A) on the back I accidentally discovered at a certain light and angle. If I ever find out who I bought from, I'll let you know if you're interested in that kind of lottery.😀
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