MCI gurus! JH110 won't rewind - no supply reel voltage!

[jdurango]

JH-110 won't rewind with REW button or MVC. FF and play works fine, transports seems happy otherwise.

- All power supply rails test fine into main board
- +15/-15v measured at pins 7 and 4 of several random TL741's tested on ATB
- REW button on transport and MVC light up when engaged
- Plugged in external remote, same....REW and MVC light up when engaged
- MVC works for forward
- No voltage to supply motor
- Supply motor works fine when plugged into take-up motor harness
- Brake is OFF - tests fine (not stuck) - either way, no voltage to motor
- On ATB I can adjust DC offset at TP1 and TP2 to 0v

Machine DOES NOT have red IC sockets. It's a very well taken care of, professionally maintained later Sony model that shouldn't have cold solder issues. Molexes wiggled, boards pulled and reinstalled (I know the routine with MCI), deoxit and stabilant applied, several IC's replaced (TL741 IC1, 2, 4, 10, 11, 13 and 14 on ATB).

I have schems but I'm having a tough time figuring out how exactly REW is supposed to engage the supply motor. I know voltage changes through the REW, things happen, and there is a motor driver board somewhere (in the PSU?) that spins the motor. IIRC the tach is just there to monitor speed in play modes, not active in the REW/FF/MVC function, but I don't know, could be wrong.


Any help is greatly appreciated! Thanks!

 

[Bo Deadly]

I know nothing about such machines but post the part of the schem for the motor driver board and power supply. Obviously the PS and motor driver boards are going to be very close or even on the same board. Are the motors AC? Maybe a dead triac? High current parts tend to get burned up inside and die after a while. Look for discoloration around the PS and motor driver parts.

 

[jans]

There is a very active MCI group on facebook.