I've seen a few different sizes used by S2G members in the repair of the GF-777.

On my first 777 I used:

FRX 11.5 - main flat drive belt

SBM 5.7 - secondary belt

SCX 7.4 - tape counter drive belt

I also ordered several SBM 5.6

On the first 777 I repaired, the 11.5 belt appeared to be correct (?)

The 5.7 belt seemed slightly thicker in construction and seemed smaller than the original. I realize the old one was stretched a bit, but the 5.7 seemed to be shorter in diameter, taking the stretching of the old belt into account.

After belt replacement both decks played a little slower than they should. I don't know if this is due to the fact that the belts are new or if they are too small and causing the tape drive motor to play slower because of the added (and incorrect) tension.

I am going to try to adjust the speed via the set screw on each motor.

Does anyone know the original specs from Sharp in regards to proper drive belt size?

Also, what is the function of the smaller secondary belt? I assume the large flat belt is for playback. And what about the idler wheels with a band of rubber around them...what is their function?

THANKS!!

C'mon guys...I'm dyin' here. I am getting ready to disassemble my "good" GF-777 and I don't want to do that until I am sure of the correct belts.

Help a brother out.

Tom, holla at FATDOG!!! I think "He's been there, Done that!"

Johnny <-gotta stop drinkin'

If its slow after replacing than the flatdrive belt might not be the right size. The width can be important too in thos case.

Also clean the pullys check for rubber stuck on them.

The band of rubber for idler might need replacement too.
Sometimes is just a small belt on there.
It usually the wheel for the takeup of the tape.
Should have a smooth pull on the cassette takeup post.

check this, check that and check some more.

Oh I do not know the right size's for that.

Thanks Transwave. I was careful to clean all of the plastic and metal pulleys with rubbing alcohol. The two idler wheels with rubber on them was cleaned and rejuvenated with WD-40. I did a bunch of research and found that many technicians rejuvenate rubber rollers this way. Apparently WD-40 is not (technically) a lubricant. It made the rubber plumper (is that a real word?) and grippier.Not slick or greasy like you might expect.

Rubber does have oil in it that dries out.
So a bit of the right oil and amount can help in this case.

quote:

Originally posted by tburick:
Thanks Transwave. I was careful to clean all of the plastic and metal pulleys with rubbing alcohol. The two idler wheels with rubber on them was cleaned and rejuvenated with WD-40. I did a bunch of research and found that many technicians rejuvenate rubber rollers this way. Apparently WD-40 is not (technically) a lubricant. It made the rubber plumper (is that a real word?) and grippier.Not slick or greasy like you might expect.

hi..TB..to rejuvinate certain rubber parts i use this product called Rubber Renue by MG chemicals....works quite well...

Yes, MG chemicals have lots of stuff for electronics repair.

Might be good to check them out.