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Sony TC-366 - belts replaced and now slows down over time

C

cptsomeone

New Member
Sony TC-366: https://www.hifiengine.com/manual_library/sony/tc-366.shtml

Finally replaced all the belts on this unit with some high quality ones from Germany.
Put it all together, after cleaning the guts inside and Deoxiting the switches and knobs.
Everything was running AMAZINGLY, super super clean clear output... and then it started slowing down during playback?

I was playing back a tape that I could compare to a digitally remastered copy, and the speed was definitely getting slower and slower as the tape played on, no matter if I stopped or started the unit again...

My thoughts are:
1. Belts getting stuck on gunk or something else on the wheels.
2. The motor was so used to the old belts that it can't handle the tension of the newer belts; so that's a motor replacement.
3. Something I cleaned caused an issue?

Any thoughts? Any photo, video or audio samples needed?
Not keen to get another unit as I'm really not invested in RTR...

Thank you all!
 
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Is the tape that you are playing an old tape or new? The lubricant on old tapes can dry out. Try it on a new tape.
Also, are the replacement belts the correct size? They may be placing undue tension on the pullies causing excess friction or bearing wear. Did you get oil into the motor by mistake, getting onto the brushes?
Check the tape back tension, perhaps the feed reel has too much tension on the tape? Try playing a recording at the beginning and end of a tape to see if it makes a difference.
 
Hi all, sorry to necro bump this old thread, I've tried a few suggestions here but this old gal just isn't having it... I think the motor needs replacing, it was so used to the old belts that it can't handle proper tension... that's my guess at least. At this point, I have no more reels to transfer, the effort and cost to replace the motor or do more work on her wouldn't make sense for me. so I'll be sending her out to pasture (giving it away for free/sell at low cost) to someone who's more willing to restore her. Thank you all for the information! I hope this helps someone else in the future.
 
The only thing that directly affects play speed is the capstan and it is not driven by any belt, so you should not have expected belts to fix any speed problem. Capstan is driven by the capstan motor and flywheel idler. So if you want speed to be correct you should have replaced the flywheel idler with new. That is the most common parts to create speed problems. Also helps speed to: replace motor run cap, rebuild motor (clean/lube), lube the capstan bearings, and replace pinch roller.
 
My money is on the motor-run cap. I know I may be too late to this thread, but just wanted to reinforce what others have already suggested.
 
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