Sony C9 Betamax tape path alignment

[TIMTAPE]

Reading the thread on the Ferguson VCR reminded me of a problem I've long had with my C9. I have no service manual for this machine.

The roller/guide on which the tape reverses direction is at the back of the machine in play mode. There is a height adjustment of the guide itself but also in the base, a tilt adjustment along the tape travel axis.

Merely adjusting the guide, has alternated between poor tension on the top edge of the tape, or the tape riding too high on the guide and creasing at the top edge. Should I be checking other adjustments such as reel table height before adjusting the guide?



Any help appreciated.

Tim

[dj_fivos_sak]

Hi Tim. You can download the manual here:
https://freeservicemanuals.info/en/s...9ESSM/SLC9ECS/

Are you reffering to the tape guide that sits next to the head drum and wraps the tape around the drum when the tape is threaded?

Fivos

[TIMTAPE]

Thanks so much for the link. Just accessed the service manual. All 296 pages of it, some in colour.

Yes the roller guide which wraps the tape around the drum.

Cheers,

Tim

[TIMTAPE]

It seems the large Service Manual needs an accompanying manual for performing adjustments.

From page 1: "Also refer to ADJUSTMENT MANUAL for SL-C9ES"

I believe the C9 was unique in having direct drive reel motors and some other advanced features but as far as I can tell, the basic tape drive mechanism was similar to other Sony Betamax models around that era (1983) so if anyone has any adjustment information relating to such a mechanism I'd appreciate it.


Tim

[8 Tracker]

Hi Tim,

Just about all 2nd generation Sony Betas used the same basic mechanism (SL-C30, SL-F30 etc.) but most used pendulum drive to the reels. The SL-F1 portable unit uses the same mechanism as the C9 with direct drive motors. Service manual for that model available here.

Do you have an alignment tape? I believe you can use a normal tape for the tape path alignment, but of course the machine will then be aligned to that particular tape and that may not necessarily be correct for compatibility with other tapes. Others may be able to confirm this.

Good luck with it, I've done several and it's not easy compared with other less complex machines. Do let us know how you get on.

Mark.

[Mooly]

Its many years since I owned my C9's but I really made an effort to understand the intricacies of these wonderful machines. Yes, direct drive motors and electronically controlled back tension from that little sensor arm that has tiny magnets acting on some sensors to generate a feedback signal. Back tension is adjusted with a preset on the servo.

Four big problem areas are:

1/ The original Sony pinch roller assembly (the later modified type) had an offset bearing internally. This means that when the mechanism locks the roller against the capstan, the pressure on the tape is biased such that it wants to run up the capstan and onto the guides of the ACE head. This feature helped prevent audio problems of the tape wandering down the head and also maintained a much better and consistent tape path travel in forward and reverse modes.

2/ The capstan can wear and become highly polished causing tape path problems. It is possible to 'refinish' these by holding fine wet/dry abrasive against the shaft and rotating it. You can get it back to a dull finish in a few seconds.

3/ The capstan has a 'tilt' adjustment and should be checked with a 90 degree jig of some sort. I think I used to use a plastic encapsulated power transistor as a block to hold against it. Long time ago and I would need one in front of me now.

4/ This is the bad one... the threading ring can crack. Watch the machine lace up and if its cracked you will see the ring behave oddly at the final stage of threading when it comes under stress. The small pop up 'guides' also used to break and there was a repair kit for these.

The adjustable guide on the entry side did have a tilt adjustment as I recall. When all set correctly the tape should run true in all modes and at all speeds. Looking at reflections on the tape surface is the best way to detect when contact has been made with the tape.

The guide flanges wear as the tape cuts into them making accurate path alignment difficult. You can just swap and move these around to bring a new surface into play.

[dj_fivos_sak]

Hi Tim. I'm pretty sure this manual will help you:
https://freeservicemanuals.info/en/s...TEM/711SYSTEM/
See pages 19-22.
Also, check this video out. I don't think that's your problem though:
https://www.youtube.com/watch?v=nfhqTBuru2U

Mooly, that's wonderful info! Thanks for sharing.

Fivos

[TIMTAPE]

Thanks all three for the advice. Thanks dj for the link. It seems just what I was needing.

Tim