Which kind of topology is this amp? (Attempting repair)

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#21
I'm having a strange problem, in a JE350 that kept overheating, I found that the PCB was literally "carbonized" between the emitter and the collector, suspected that because on diode mode there was something like 10K between them, I "digged" the pcb so now there is a hole between them, so no more 10k readings, but now what seems strange is that in diode mode, on the working unit I keep reading 1,7K C-E, and no reading on the substitute I soldered. Once the optocoupler was replaced almost every "cold reading" is ok, except for this, I did the same reading on an unsoldered mje350 and there is no reading, the original was a on JE350, to-226, the substitute is a MJE350, I think It's the only replacement that can be found, but this reading doesn't makes sense to me. I remember that in one of my attempts when powering the unit, sparks could be seen in the pcb between the 2 legs so, It stand to reason that this could have been one of the problems, pcb destroyed and making some strange contact with residues left by the pads, etc. Should I look for exact replacements from on semi or mje350 is OK?
Kind regards.
 
#23
It was a "glitch" on my DMM, as I said on one of the replies, this DMM is old and needs replacement, I managed to get my hands on an old but very reliable "analog" multimeter, the one with the needle and If I remember correctly, the first one I was taught to use, this one has capacitor measurement, once the semiconductors and the resistors seems to be OK on readings, It's time for the capacitors. As I said, the reading was a glitch on my dmm, tried again yesterday several times and now no reading, this is maybe, one of the reason I'm starting to look at the capacitors, some of them where changed, mostly the electrolytics, but the small ones, typically nF and so on, remain untouched, so I will test them, thanks for the tip.
 
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