Hi all. I have just restored an Aiwa HS-PL55. First thoroughly cleaned the board and recapped, but had issues with no audio on right channel and some volume issues on rev playback. Traced these down to a a couple of bad resistors and weak pins on IC1, but after a reflow and sorting out some traces and an open via, everything started working nicely - perfect and crisp stereo sound on both directions and both channels. I thought I was finished, but after playing for a while I notice a few problems: 1. Whenever I've played music for a bit (listened a few hours today) and the circuit warms up, the "rise up" effect (when changing sides or resuming from ff/rew) is really slow and distorted. It takes 1-2 seconds to reach normal volume, but then its clear. 2. If I continue playing for even longer, eventually the audio starts distorting and lowering volume. 3. If I leave the unit stopped for a minute the issue is fine when I play again. But eventually the problem returns. The longer I leave it off, the longer it will play until the issues return. My suspicion is the Q4/Q5 mute modules but I am not entirely sure how to approach this. It was my first time working with Aiwa (usually only mess with Sony), and my first time doing such an indepth repair on a PCB. It's perfect apart from this issue so I am hoping for any guidance or advice on where to start and what the issue could be. Another minor issue which - on some tapes there is a minor crackling/popping that can be heard on quiet parts of the tape. On other tapes or without any tape, it is completely silent. The tapes which have the popping sound don't do the same on other devices. Any clues on this would be helpful too. Thanks!
Regarding potential common problems, what I would check are pads of capacitors that leaked. Seen on these seires that hairline cracks thend to develop right at the interfact between the trace and the pad, crack not really visible to the naked eye until the solder mask is scraped off. As for Q4,Q5 muting transistors, you can remove those and short the drain with the soruce. See if the problem goes away.
Thanks @Valentin. In the meantime I reflowed the Q1 rapid rise up switch, along with Q4 and Q5 - the problem seems to have gone away, at least for now. I will see it how goes and if it returns will double check the pads.
