First post, by NooN
Hello guys,
I just took an old LAPC-I from the attic and put it in a 486 machine I was working on.
Initially it worked flawlessly, but after taking the motherboard out to fix the damage done by a Varta, it behaved strange.
It's like a feedback sound coming from a microphone. It builds up and after about a second (maybe attack phase, maybe echo module processing the sound that's coming) and then it stays like it is and sounds like it is looping - a looping microphone feedback sound! You can still hear music from games, but that is barely audible below that noise.
I checked the board, found a bent pin at the height of a Mitsubishi amplifier (not sure if it even had contact!), but a destroyed amplifier doesn't make sense (in my opinion). The sound comes from both channels (I think the amp is mono), so I think the cause may more be the echo module or the LA logic, or maybe a faulty RAM chip.
Issue is always the same when powering up the machine. Does anyone have a clue for me where I could look for the issue? Or is anyone able to check and repair it? (would pay for it).