nielsk

Looks like a bad capstan motor here, trying to confirm. No capstan action. It keeps blowing the complementary pair motor driver transistors on the capstan driver board, I replace them and it tries to move for a second... blows again.
It is very easy to get to the motor windings connector, it is on the right edge of the tacho board just under the capstan motor. It is the 3 pin connector, you can unplug it & plug it back in without removing anything. So... if anyone has access to one and will take resistance readings across the 3 contacts and report back that should help confirm if this motor is toast...
Anyone know of a place the rewinds these?

Thanks!


PRR

Can you spin it with your fingers?

radardoug

You can test it with a variable dc supply. The last spooling motor I changed on an 827 blew up the drivers, they fail badly.

Gold

Athan will rewind the motors. I ‘ve had four A80 capstan motors rebuilt by Athan and have been happy with the  work. The two best tape machine techs in NY also haven’t had any problems with them.

Precision Motor Works used to be the go to place but he is semi retired and cranky.
« Last Edit: December 04, 2018, 11:33:52 AM by Gold »

nielsk

It spins just fine.
There are 3 taps, each fed by a driver pair (methinks different combinations for different speeds)
Do you suggest trying applying DC to any 2 at a time?
It would be nice to know what resistance the taps should be reading...

radardoug

Ah yes, its a 3 phase motor, but look between all possible connections and meter the ohms. If they are not the same, you have a problem.

nielsk

I was finally able to test a known working motor capstan, posting the results here so anyone else encountering this may have access to the data.
 The windings all read right about 8 ohms, tap to tap. This is correct.
I was able to get the problem on this machine down to the Studer programmed chip on the driver PCB, now to see about their repair / exchange service! (fingers crossed)


 

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