I'm working on a Sony TC-660 tape recorder and am in need of a service manual. Is there a Sams out there that covers all serial numbers since the number on mine is missing. Low audio record on left channel forward direction only. All else is fine. I suspect an elect. cap has dried out and has gone open which is common for machines this old.

Any help ??

Regards,

Jim L.

There is no Sams on the Sony TC-660.

Sounds like that could be a worn or slightly dirty head.

Naw, that wouldn't be it because playback in both directions, both channels using a full-track alignment tape is fine out to 15kHz. Measured bias to both heads in both directions on record is at the same level. It's basically a two-head (erase, R/P) for each direction machine so many gain stages share record and playback roles. The R/P switches are clean as are the other controls and trimmers.

Jim L.

Jim,

I'm going to rain on your parade a little. Playback levels do not stand as proxies for recording capabilities. If you've seen thousands of reel-to-reel tape recorders like I have, you've learned the hard way that a worn record/play head will often be capable of acceptable playback performance, but will render much poorer response in record -- and this disparity will usually show up more in the left channel than in the right.

This appears to be the combined result of a several factors. First, the pole pieces that constitute the gap on Sony heads are not parallel. As a result, Sony heads experience a widening of the gap as the heads wear. Second, Sony heads use a softer alloy than other brands, most notably Revox, thus making the heads more susceptible to wear. Third, the left channel lies on the edge of the track that the tape wears into the head. For this reason, when the tape rides up of the flange of the wear track, the tape will lose intimacy with the gap in the left channel more than with the gap for the right channel. Fourth -- and this aspect affects both channels -- the wear track is not created by a machinist. It is the result of friction from the tape, and because there are a lot of random or semi-random force vectors generated as the tape presses against the head, the smoothness and evenness of the track is always imperfect.

I've encountered many hundreds of sets that functioned just like yours, where the problem ultimately came down to a worn head. Sadly, Sony no longer supplies those heads. I personally bought the last known handful of them from Sony's Kansas City national parts depot about a decade ago.

There are only two solutions I know to this problem. First, you can look for a low-wear parts machine. Second, you can hang out on eBay and hope. I personally own a couple of Sony reel-to-reels with near-new heads that I keep SOLELY so that I can repair decks with worn heads.

Regards,

Fred
owner
Classic Audio Repair