Good day. I hope all is doing well on your repairs. I am working with a Firland Extreme 1200D mono amp. It had a blown 1 rail capacitor 1500uf /80v but i replaced all 6 of them, Power is normal . blue light and no protect issue but no audio output. I checked the output FEts IRF260M , 2 lows and 2 highs driven by one IRS214S and found out they switching is not normal. I removed all output FEts and the driver is producing good drive signal to gates of Low side. I fixed 2 FetS (1 low nand1 high) and the switching is normal on Hi and Lo. But when i fix all of the FEts it is not switching normally, some sort of noise in the signal and you can hear hissing sound only on the output. I replaced also the drive chip, checked the outout FETS are all good but stll same issue. Please refer to the Pictures. I checked all output components i believed are all good, Rail voltage is good as well at 114Vdc. It is frustrating sometimes that expecting a direct repair but its not even if you know that you are doing well on hours of repair ha ha. Did anyone encounter this issue?
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Will it run normally and produce normal audio with a light load with only two of the FETs in the circuit?
Was the waveform with or without the FETs in the circuit?
Was the waveform with or without the FETs in the circuit?
the waveform is with all the FETS installed. Clean audio wave signal I see when using only 2 FETs., but did not try audio test Only 50 HZ sine wave. working normally as i increase the gain without load.
another thing, found out and measured DC offset 3.5V dc at speaker terminal output when all FETS are installed.
Sorry this was on me, I resoldered again the power caps 6 1500uf/80V , because I saw lately on the old caps legs (2 caps) I replaced that there where pulled out vias. I made sure the connection on each side of the board and that solved the problem. Amp now is alive and kicking.
