Poor rewind performance

[stragulus]

I've rebelted the bottom deck with fresh new belts of the correct size (FM9.6 + SBS8.9), cleaned all the gears in both belt's paths, and everything works. However, rewind performance is not good. With a 90 minute tape, it will work until it's within 10% at the start of the tape, then it doesn't seem to have enough torque to keep it running.

I've tried varying belt sizes/tensions, removing the counter belt for a little less resistance, but nothing really makes it work well. Even swapped out the motor with a beefier one, tried different tapes (it varies a little amongst them); no dice.

Does anyone have a C100/clone that does NOT have this issue? Is it just a weakness of this box/deck?

 

[baddboybill]

I cant seem to remember the c100 deck but many issues like this are due to a dry cracked tire that is used on reels. Its best to remove deck completly

 

[stragulus]

This deck doesn't have those, it's all plastic gears and springs. The only rubber is the 2 belts and the pinch roller. It seems that 1 gear that shifts when you press rewind is very sensitive to the correct tension. When looking from the backside of the box it's the top-right one on the secondary (non-flat) belt. This gear hooks in on the gear on the rewind spool. It could be worn out springs, it could just be extremely picky about belt tension, but then I'd imagine the deck wouldn't perform according to spec very long. Which is why I'm wondering if anyone has a deck that doesn't have this issue.

 

[hopey]

At risk of being contradicted re build your motor. Full torque is avaible at locked rotor but top rpm is compromised by friction or a bad commutator.

 

[caution]

I have this issue as well but never bothered to figure it out. I had my money on too much friction or old grease between one of them there plates in the core of it, but looked like a royal pain to disassemble.

 

[hopey]

Hang on a sec this maybe a brake on the fly wheel issue?

 

[baddboybill]

Next step i say is pull off the reels and clean underside as dried grease might have formed causing the friction. Ive had to do this on 3 other decks and it worked like charm.

 

[stragulus]

Next step i say is pull off the reels and clean underside as dried grease might have formed causing the friction. Ive had to do this on 3 other decks and it worked like charm.

Good point. There is one gear that drives a worm wheel that has a lot of old grease gunk on it. Although it seems to rotate without much resistance just fine and the grease looks..greasy , I'll go and clean that one and see if that has any effect.

I have meanwhile found belts that improve the performance significantly. I think the SBS8.9's are too tight (I have tried fresh ones from 2 providers), especially for the counter belt. I have put an SBS9.2 that I happened to have for another boomer on the 3 gears. This gave it a little extra performance. Then, I also replaced the counter belt with one from a generic set of belts that was a little bigger and not as tight, and it now works almost as you'd expect. It still struggles a bit at the start of some tapes that are somehow more resistant, but it does rewind them fully now.

 

[baddboybill]

I only replace counter belt if it dont work or is missing as it dont need to be tight to work properly and an old thin belt keeps any pressure off reel

 

[stragulus]

Yeah I don't always replace those either, but on this king of boxes I feel I have to. It works the same with or without that belt now though so that seems to be good. But the SBS8.9's are def a little too tight for this box. It is very picky.

 

[stragulus]

I got the deck working perfectly with the SBS9.2 belt (which had the biggest effect) and cleaning up the goop/regreasing around the worm wheel. Performs like new now, thanks for the help guys!

 

[ariesman72]

Wow ! You guys are awesome I wish I knew you back in my school days.

 

[Transistorized]

I must've got lucky. I installed the SBS8.9 and mine will rewind a 90 minute tape from start to finish but it definitely slows down and if you stop it towards the end or try to do a rewind music search towards the end of a 90 you can forget it...lol

Both of my C100's do this and every one of them I have worked on/seen does this too. It's the Conion curse

 

[caution]

I posted a fix for this in strag's other c100 thread. You need to stabilize the tape run pulley shaft, which doesn't stay straight with a belt pulling on it. It starts rubbing against the inside of the gearbox. Center a washer with a hole ever so slightly larger than the shaft and secure it on the back where it sticks out.

 

[Transistorized]

Interesting Caution. I'll check on this with my boxes