Teac A-7300 capstan problem

Musicalme

Musicalme

Relearning my trade
Hi guys
I recently aquired a TEAC A-7300 and am in the process of restoring it. I have cleaned it out inside and I noticed something bad wrong with it. The capstan motor (direct drive) was seized :( So I pulled the motor apart checked it over and cleaned and relubed the bushes (I used a light machine oil). It spins freely now and runs up to speed when you switch the deck on. However...... this is where it goes south. When you engage play the pinch roller comes up and the capstan slows to a stop.
When you stop the machine the capstan fails to start spining again and needs a bit of a flick with your fingers to get it going again.
It seems the motor doesnt have the torque it should. I have checked the voltages to the motor control board and they are as per the service manual. The control board is mounted on the side of the motor.
Does anyone here have any idea as to where I should start looking?
TIA

Ray
 
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You have a special motor in that model partsnr # 71060070
Only 25-2 and 7400 RX has the same motor.
I recieved your email this morning, but can't help with a replacement, sorry
 
Yep I guessed as much trust me to get something odd and rare :(
Just a question. I have pulled it apart again and for the life in me cant see anything wrong except now with all the pulling apart its a bit more free.
Looking at the service manual I have tested the windings and all looks good.
I plugged it back in and it speeds up ok and slows to low speed when I select it and quickly back up to high speed again when I switch back.
How much torque are these motors ment to have? I can stop it with my fingers but it takes a considerable amount of force to do so.
 
That particular motor has 400 G-cm torque (24 volt)
Did you try to adjust the adjusting screw for capstan shaft ?
 
Yeah I tried that. What sort of lub should I have put on the adjuster at the back? bit of grease? Also how much is 400g-cm? Sorry I'm a bit of a dumb ass.
 
If the capstan motor has weak torque, then the motor drive board probably was damaged when the motor bearings froze up (too much current draw with the motor stalled). Check for off-color resistors or transistors (due to heat). Check resistor values...especially the larger resistors. Test transistors.
 
Well all the resistors look ok no heat damage. Some of them test out of spec I think (testing in circuit isnt good) I'll have to test these out of circuit. The big 2W 4.7ohm resistor tests at 5.1ohm.... hmmmm bit high. All transistors seem to test ok. The caps?? yeah well all look good but I havent tested them. I might just replace them (electrolytics)
I'll get back to you. BTW thanks for the help.
 
The 7300 used the DC capstan motor well known for having this issue. Did you try Teac? They're phasing out most of the parts for their R2R line, but they may have a motor for you.

parts@teac.com
 
Got it running guys. Some caps were way out of spec. I changed them and it seemed to be better so I tried it in the deck and it still slowed down but not as bad. Slight adjustment of the pinch roller and away it went. :)
Thanks for all the help and/or moral support ;)
 
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