Sony TC-645 tape recorder mod

[lcsaszar]

I own a Sony 3-motor 3-head tape recorder and I would like to modify it. The problem is the supply reel has a primitive friction torque regulator that does not work perfectly. The phase between the L and R channel varies, but it is stable if I brake the supply reel by hand. Also at fast winding the supply reel is free running, and the tape is taken up loosely. I am thinking about a mod where the supply reel motor gets some voltage (like the takeup reel does) that would provide some torque in order to pull the tape. I think even unregulated it would work better than the current felt brake.

The idea is that the takeup reel motor gets full voltage for fast forward wind, and decreased voltage at playback. I want to do the same for the supply reel motor. Unfortunately I have no circuit diagram for the machine.

Could anybody give me some advice, how should I do the switchover to a lower voltage? I do not want to trace back the takeup motor circuitry, only as an ultimate solution. I think most 3-motor Sony tape recorder circuitry of that product range is similar, being only cosmetic difference, so any other Sony circuit diagram will give some idea.

 

[circuitexplorer]

TC645 schematics

Are you still looking for schematics of the Sony TC-645 open reel deck?

Message me with an e-mail address and I'll upload scans of the service manual to megaupload or another bulk fileshare service.

 

[lcsaszar]

Hi circuitexplorer,

Thanks for your kind offer. I was able to calibrate the machine, and I would like to modify the tension reel motor circuit. I could not send you an email via the forum, therefore pls contact me, my email is lcsaszar at freemail dot hu TIA Laszlo