JVC M90 MMS music search problem.

[Tinman]

Hey guys,
I have an M90 that's been a bear to get working.
Currently I'm working on the cassette player.
I cleaned and replaced the belts then found it had a power problem.
I was able to track that down after more hours of troubleshooting than I care to admit, luckily I have another M90 that I used for comparison.
The cassette player is working and sounds great but the MMS isn't.
I checked the MMS board any everything checked out ok.
I tried the other cassette player with this MMS controls then put the repaired player back in and switched MMS controls and neither combination worked so I believe it's a problem with the MS signal coming from the pre amp board.

I figured I'd ask if anyone has experienced an MMS problem like this or if anyone can point me in the right direction to look for the problem.

I know the music search isn't an important feature but I like to try and get everything working if possible.
Thanks.

 

[Tinman]

I removed the amp & pre-amp boards yesterday to check the voltages at Q506 and found the legs were rotting away.
I have no idea what caused it but have a new transistor on the way which should get the music search up and running.
Assuming it works with the new transistor, this'll be the easiest and cheapest fix on this box so far.

 

[Brutus442]

Impressive troubleshooting!

 

[docs]

Good job, hope that resolves it and there is nothing else causing it to blow.

 

[Tinman]

Thanks guys.

I finally received the transistors today.
I soldered one in, reassembled the amp and pre amp boards and tried the music search.
Thankfully it worked.
I wish every problem was this easy to resolve.