Sharp GF 8686 - gooey capstan rubber issue and speed

Hoping I can get some help on this, not been on here a while but following this topic below I finally got round to getting this back together:

viewtopic.php?f=2&t=14279

Before strip down speed of tape playback was fine but as with most old Sharps the capstan spindle drive rubber was screwed. I have replaced it with a short piece of silicone rubber tube as usually recommended and very carefully put everything back together. Also included new drive belts all round (5 % shorter than old ones). Tape playback now works great and no chewing tapes BUT it is s-l-o-w...

I took it apart again to check everything and thought maybe the rubber may be rubbing inside the (not sure of name) capstan housing - the part that the flywheel/spindle rotates inside with the opening for the drive tyre to move against.

I cut the rubber down so it was only as long as the window.

Back together and a definite improvement but still too slow. With drive belt removed the spindle rotates freely.

Any ideas please?

Oh and how long should the silicone rubber tube part be (whole length or just the window length)? Does the external diameter of the hose have to be an exact size?

Did you clean inside where old wheel melted? Also did you sand the new wheel ends and surface? Try cleaning the tire that runs on wheel as well as take up reel surface that tire runs on. . Good luck!!


Bad Boy Bill

I did one where the rubber was still intact so I had something to check the length...it was about the size of the gap not the full length

baddboybill said:

Did you clean inside where old wheel melted? Also did you sand the new wheel ends and surface? Try cleaning the tire that runs on wheel as well as take up reel surface that tire runs on. . Good luck!!


Bad Boy Bill

Click to expand...

Hi, many thanks, yes all cleaned and spotless. I did not sand the outer surface/diameter of the piece of silicone rubber (the *ends* of the tube do not touch anything though??). The outside of it is quite grippy and is not slipping on the capstan 'tyre' which is in good condition and cleaned.

Mick said:

baddboybill said:

Did you clean inside where old wheel melted? Also did you sand the new wheel ends and surface? Try cleaning the tire that runs on wheel as well as take up reel surface that tire runs on. . Good luck!!


Bad Boy Bill

Click to expand...

Hi, many thanks, yes all cleaned and spotless. I did not sand the outer surface/diameter of the piece of silicone rubber (the *ends* of the tube do not touch anything though??). The outside of it is quite grippy and is not slipping on the capstan 'tyre' which is in good condition and cleaned.

Click to expand...

How's about cleaning the take up reel surface tire rides on Are belts possibly to tight. This will also cause it to slow down. Also have you tried different cassette tapes. Some tapes are sticky and can cause slow running in play, FF and Rew.....


Bad Boy Bill

Does this model have speed adjust for the deck motor?

Thanks Bill, will check that and let you know, pretty sure it must be dragging somewhere as all was fine before speed-wise...

Getting nowhere! Had it in and out a few times - cleaned all the wheels/tyres etc - everything seems to be running fine, tension good - but still slow...

If you can't find a speed adjustment trimmer on the circuit board; check the motor itself. There should be a little hole on the backside that you can stick a tiny Phillips screwdriver into; that's where the trimmer for motor speed resides. I've had to do this on virtually every tape deck I've ever re-belted. Good luck!

Oh yes, one more thing: if things are gunked up, too tight, not moving freely; you'll hear a lot of wow and flutter when you play a tape; i.e. an inconsistent warbling sound. If the deck sounds fine other than just being slow; you're golden on the mechanical side. Also stick a finger in the hubs of the tape itself and make sure both are turning freely. If not, whack the tape against the palm of your hand a couple times and check it again.

I know how to fix most of the problems of GF9696F deck, but not familar with GF 8686.

If rpm is slow and "steady", then it might need internal trimming for the motor speed. like agc mentioned.

Also, check to make sure the tape counter isn't dragging or seized, that can drag too sometimes. Also, if the belts are square, make sure theya ren't twisted whem rethreaded onto the wheels. that can cause drag too. Maybe you covered it already but just trying to eliminate all possilbe. Also, even a small amount of grease from you fingers can cause belt slippage & thus less torgue is transferred & less speed results. Good luck. I've never worked on an 8686 so mostly guessing.