Tascam 488 troubleshooting question

[Frank Wild]

I replaced the belt. It's all up and running, although I haven't checked any record functions yet. Meanwhile, in PLAY, on tracks 6 and 7 the VU meters show a signal, and I can hear those recorded tracks through CUE, but not through MIX. Running faders 6 and 7 up and down gives nothing at all, so I don't think that DeOxit will help. Should I look for cold solder joints? But where?

 

[sweetbeats]

Did this issue exist before the belt swap?

 

[Frank Wild]

I don't know, unfortunately. I replaced the belt first thing. There was no way to check playback without a new belt.

 

[sweetbeats]

I’d start re-seating connections. Follow the wiring diagram in the service manual and carefully disconnect and reconnect connectors.

 

[Frank Wild]

It took me a long long time to diagnose and repair these two dead tracks. It was the 8-pin op-amps on the mixer circuit board. They're no longer made, but can be found on eBay. In fact I am selling a couple new ones on eBay right now.

 

[sweetbeats]

Thanks for following up. Are you talking about the 4565 SIP-8 parts?

 

[Frank Wild]

No, these were U602 and U702 on the input board, Mitsubishi M5218L 8-pin op amps. I also replaced a couple nearby electrolytic capacitors, but probably didn't need to.

 

[sweetbeats]

Interesting. I think those are input amp stages to the pair of AN7367 Type II dbx processors.