"Alan 'A.J.' Franzman" wrote in message
news::
"Mark D. Zacharias" wrote in message
m:
"Alan 'A.J.' Franzman" wrote in message
news:jqu6h.5614$dh7.191@trnddc01...
I have a Sony TC-K620 tape deck with an odd power supply problem. I could
use a scan of the schematic or service manual if anyone can send it to me.

The problem is, it does not shut off completely when switched off. The
cassette well backlight glows dimly and the capstan motor runs slowly when
"off".
snip

Sent the s/m to the verizon acct. Hope it got through.

For anyone else having this problem (there must be others!):

After printing out the relevant part of the schematic and studying it for a
few minutes, the first component I looked at on the board turned out to be
the culprit -- R216, a pullup in the power control circuit, is a 22k
instead of
2.2k as called for in the schematic, apparently due to a factory assembly
error. Paralleling a 2.4k resistor with it kills the capstan motor and
backlight and brings every supply voltage down to near zero but one (the
-28V only goes down to about -3.5, but that's a lot better than it did
before. I'll do some more checking to see if there's anything else amiss.)

I'm off to do the fix now, thanks again for the help!

On yesterday's inquiry from another TC-K620 owner with the same problem,
re-investigation reveals that I mis-reported the part number; it's R816, not
R216, which was a 22k (red-red-orange-gold) instead of 2.2k
(red-red-red-gold). This is near the back corner of the mainboard, left-hand
side if you're facing the front of the unit.

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Alan "A.J." Franzman

Email: a.j.franzman [ A T ] verizon [ D O T ] net

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