Hello everyone, I want to tell you about the problem, the 47 ohm resistor burns on the positive part, at first it burned on the negative part, well, the problem was mps a92, after replacing it, it changed, I don’t know where to look for it and what to do, I will be grateful
Seen from here, I see two HS resistors, one very black and the other which has taken a heatstroke.
Can you locate them on the schematic ?
Can you locate them on the schematic ?
You didn't describe your current symptom after replacing MPSA92. We need some direction to follow.
I'll make some comments and guesses to get started.
It would be nice if the schematic had reference designations to make discussion easier.
Because both 47 ohm resistors are damaged, I suspect both final transistors are failed; if their base-emitter junctions were intact, the 47 ohm resistors couldn't have been damaged--- they wouldn't see more than about a volt across them. So remove and test both final transistors. I think you can troubleshoot the amp without them being replaced--- just don't load the amp output. And there's less risk of damage without them.
Assuming the 47 ohm resistors have been repaired, what output voltage do you observe?
Thanks.
I'll make some comments and guesses to get started.
It would be nice if the schematic had reference designations to make discussion easier.
Because both 47 ohm resistors are damaged, I suspect both final transistors are failed; if their base-emitter junctions were intact, the 47 ohm resistors couldn't have been damaged--- they wouldn't see more than about a volt across them. So remove and test both final transistors. I think you can troubleshoot the amp without them being replaced--- just don't load the amp output. And there's less risk of damage without them.
Assuming the 47 ohm resistors have been repaired, what output voltage do you observe?
Thanks.
Sorry, I didn't write the symptoms, so I'll explain the story
the amplifier worked, then there was smoke, it turns out that it is being repaired, it is a Chinese transistor, a faulty copy of the 2SC2922 transistor and the second original, they put a 4 band 5% resistor (there were 6 4 pieces (470) 2 pieces (47)) Replaced it with a 1% 5 band , for this they sent a full pair of original transistors, I did not risk soldering,
I turn on the amplifier and resistor 47 is lit, I realized that I need to check the cascade
I found a punctured a92 there, ordered a pair of a92 and a42
then the opposite 47 ohm is on
checked the whole amplifier, only in the working channel I found a 47u capacitor, it was like a resistor, not in the working channel was 47, it had a capacity of 33
I checked if everything works, maybe some copmonet changed the parameters or it changes when everything is turned on
therefore turned to specialists
the amplifier worked, then there was smoke, it turns out that it is being repaired, it is a Chinese transistor, a faulty copy of the 2SC2922 transistor and the second original, they put a 4 band 5% resistor (there were 6 4 pieces (470) 2 pieces (47)) Replaced it with a 1% 5 band , for this they sent a full pair of original transistors, I did not risk soldering,
I turn on the amplifier and resistor 47 is lit, I realized that I need to check the cascade
I found a punctured a92 there, ordered a pair of a92 and a42
then the opposite 47 ohm is on
checked the whole amplifier, only in the working channel I found a 47u capacitor, it was like a resistor, not in the working channel was 47, it had a capacity of 33
I checked if everything works, maybe some copmonet changed the parameters or it changes when everything is turned on
therefore turned to specialists