General > General Technical Chat
Akai motor run capacitor
bdunham7:
--- Quote from: HendoNZ on July 05, 2021, 10:07:53 am ---So I shouldn't replace the old can with two similar size (uF) caps? If it ever got switched to 60hz then there would be a 3uf cap there instead of the 3.5uf. I would have thought that all it'll do is run slower.
--- End quote ---
If you use the 3uF and 2uF caps wired just as the original, it will work perfectly at 50Hz and might have slightly less starting torque on the 60Hz setting. I think this will be fine. What parts of the deck does this motor drive?
HendoNZ:
It drives the capstan - I'm replacing a 4uf X 2 cap that drives the reel tables (one for each motor) to try to eliminate a back tension problem.
I reckon the reel tables capacitor is losing torque and not providing enough back tension to the tape causing the left channel to drop out. (How I came to this conclusion - when the channel drops out; if I put some drag on the supply reel the channel comes back. Also the find and fast forward start fast then get progressively slower)
And so if I was going to change the reel cap, I might as well change the capstan cap.
A bit more info then was asked for.
bdunham7:
--- Quote from: HendoNZ on July 05, 2021, 08:02:45 pm ---It drives the capstan
--- End quote ---
Is there a belt that is repositioned when you change from 50 to 60Hz?
andy3055:
That left channel drop out may be because the pinch roller rubber has become hard. In a deck that is this old, that will be the most common issue. When the rubber becomes hard, the capstan will not be able to push the tape fast enough. That will be also contributing to a lack of apparent speed. It is easier to suspect the motor caps but they last much longer than the rubber pinch roller that gets hard with time. You cannot use any sort of rubber rejuvenater as that will get on the tape and ruin it. Best solution is to replace it. Check all the tape guides as well and make sure they are clean.
If you replace the caps with anything other than what is specified in the circuit, you are bound to have speed variations/problems which will be hard to figure out and correct.
One more thing to check would be the felt pad (if they ere there) clutch mechanisms on the feed in and take up reels
floobydust:
You can look at the tape travel, it's not supposed to move up or down with different back-tension unless something is crooked or out of alignment. One channel should not just get quieter or cut out completely.
Note different resistors R2+diode D1, R4 for 240V as well, this affects the motor braking and I haven't figured out how they are doing back-tension here.
The GX-630D has a 50/60Hz switch for the same 24XO-TD reel motors, for 3uF or 4uF.
Careful the motor portion can be hazardous live if the mains cord is flipped.
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