[Jaypee]

Since my M³ PCB's haven't arrived, I need to get working on something. I have this old Philips amp from the 80's (I think) and it's been working like a charm until now. It all began when I accidentally unplugged the cable from my computer soundcard while the amp was still on. It took somekind of static interference from the input plug as it hit the computers case, both 2,5A (part no. 1501 & 1502) fuses blew instantly. When I replace the fuses, with nothing connected to the amp, it blows the fuses as soon as I swich power on. The computer was the only thing connected to the amp when this happened, and it was connected to the "c-disc/TV"-input.

Since I'm not too good with error diagnostics, I was wondering if anyone here could help me get it running again? Link to the service manual of the amp

I'm thinking could the STK2125 be fried, and is there any way to measure it? If you have something else in mind that I need to check, please contribute.

 

[mono]

STK2125 being the output power amp IC, yes it seems there is a good chance that is the problem. I'd probably desolder and pull it off the PCB and measure supplyl voltage, and L/R signal strength at it's input (I mean the now empty spot on the powered PCB - being careful since there could be high voltage exposed, I didn't check that aspect), and if those look reasonable then jumper wire from the input pads to a sensitive pair of junker headphones to see if the audio is making it to that point in the circuit ok.

I wonder if it's worth the trouble though, hunting down an STK2125 or whatever is failed, if the amp is so sensitive to be failure prone on the input, plus only 25W (?) ancient amp chip, and probably dried up electrolytic caps after 20-30 years.

 

[Jaypee]

Yeah, there's no finincial value here what so ever, but it's a good practise piece for me to enhance my troubleshooting skills.. I'll solder it off the board today, try to put power back on, if the fuses still blow, then there's a short somewhere else..