Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old December 14th 15, 12:47 PM posted to sci.electronics.repair
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Default Sony TC-208 Eight-Track Deck

On Monday, October 12, 2015 at 7:44:43 AM UTC-6, Madness wrote:
After a bit of hair-pulling, I was able to remove the E-clip holding the
assembly. Relubed it w/ white lithium grease, but it didn't make much of
a difference.

Regarding the motor, yes it uses 20v (outlined in the service manual) &
has a rubber plug on the bottom, but I can't figure out how to get it
out. W/ a voltmeter across the motor, & running w/ no load, I get a
steady 21.2V. Would the voltage vary if the motor had speed issues? It
does do so, under load, in time w/ the audio fluctuations. But I can
also make the voltage drop under no load by pressing down on the pulley.

Another possible problem is that the center of my capstan is quite worn
smooth. A website (8trackavenue.com) suggests "roughing" it a bit w/ a
scouring pad inserted into the front of an empty cartridge. Gonna give
that a try, too.

Strangely, the deck will play w/o any trouble if I turn it over sideways.

On 10/12/2015 7:54 AM, Bruce Esquibel wrote:
wrote:

Lubrication issues? Sounds like the capstan might be wobbling in the bushings.
If the belt turned to crud you can be certain the lubes are bad too.
Sony is notorious for using lousy lubricants even in $100,000 broadcast
machines.


Not sure about this but figured I'd toss it out.

Didn't most of the 8-track players use a self-regulated dc motor?

I don't remember what the exact name was but they were 12v dc motors that
had a built in regulator/speed control and you normally applied 14~20 volts
to them.

Usually on the flat side (opposite the shaft out side) there was a label
covering up a hole for a pot, to set the speed.

Although after all these years it probably is a bering/lube problem but the
fact that it worked a week or so before this symptom cropped up, seems a
little strange.

Kind of have a feeling it's something with the regulator circuit board
inside the motor, which even back in the day means the whole motor needs to
be replaced. Seemed like trying to take them apart pretty much destroyed
them.

Just a thought.

-bruce




Almost 40 years ago, when I used to fix these things for money, it was almost always a traction problem caused by the capstan being overly polished. I tried fine emery cloth, but what worked great was:
- remove the capstan with its drive pulley.
- put it on a record player turntable and get it spinning.
- heat up the polished part of the capstan shaft with a propane torch until it would glow dark red for a few seconds.
- the spinning is an attempt to prevent warpage.
- let it cool and reassemble.

The surface will now be a dull matte finish and the traction problem is gone. Never had to do it more than once in the life of an 8-track player.

Hope this is of interest.

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