Sony TC-RX470 Cassette deck motor replacement
Andy Cuffe
>
> This deck has a bad capstan motor. The internal speed control IC (C1470) is
> charred. If I bypass the speed control circuit and apply 12V directly to the
> windings, the motor spins. I can't find this IC anywhere (Even the IC Master
> doesn't list it), so the easiest solution seems to be to just replace the motor
> with a generic (Mabuchi), but there are a couple of things I can't figure out.
>
> 1. The motor that I want to replace is apparently made by Matsushita or some
> subsidiary. It has a number of MMI-6S2LK on it. It also says 12V DC. I can't
> locate a direct replacement (I'm sure Sony would have it, but I bet they would
> be expensive). MCM carries the Mabuchi replacements that are physically the
> same size, have the same rotational direction and voltage, but I can't be sure
> about the RPM. Is there some kind of cross reference between these two brands,
> or is there a way to "read" the model number of the old motor?
I can't help you with the speed of the motor. They are adjustable, so
it will work as long as the required speed is in the adjustment range.
You could try measuring the speed on the working motor. One way to do
this would be to paint a dot on the flywheel or belt and see how many
times that goes by in a min, the multiply by the ratio of flywheel or
belt size to the motor pully.
> 2. The deck is a dual capstan, auto reverse unit. Since there are
only two
> wires going into the motor, I assume that the deck reverses polarity
on these
> wires to achieve the reverse play. However, that does not seem to be
the case
> according to a voltmeter. I read approx. 12V at the motor connector
any time
> the deck is on. The capstan drive belt seems to turn both flywheels
and
> capstans in the same direction, and the head rotates, but I can't see
what
> causes the tape to travel in the reverse direction. Am I missing
something
> about how this autoreverse works? Is it possible that I overlooked
something in
> the way the capstan belt was threaded? I do notice that the deck only
engages
> the pinch roller that is "pulling" the tape at a given time.
>
> Any help is certainly appreciated.
>
> David
If you look carefully, you'll see that the capstans are rotating in
opposite directions. Applying reverse voltage to one of those motors
would probably blow the driver IC.
--
Andy Cuffe
balt...@psu.edu
Sofie
I would like to suggest that you at least get a price and availability from
SONY for the proper motor. It will mount, fit, and work properly without
any fiddling around. At least with the price in hand you will know how much
fiddling around you will want to do trying to obtain a replacement that may
not fit or work properly and then messing around with the speed and polarity
for your auto-reverse deck. It may cost more to NOT do it right. I have
been there before with other projects.
Best Regards,
Dan Sofie
Electronics Supply & Repair
==============================================
Dsb3283 <dsb...@aol.com> wrote in message
news:19991201234202...@ng-bj1.aol.com...
> This deck has a bad capstan motor. The internal speed control IC (C1470)
is
> charred. If I bypass the speed control circuit and apply 12V directly to
the
> windings, the motor spins. I can't find this IC anywhere (Even the IC
Master
> doesn't list it), so the easiest solution seems to be to just replace the
motor
> with a generic (Mabuchi), but there are a couple of things I can't figure
out.
>
> 1. The motor that I want to replace is apparently made by Matsushita or
some
> subsidiary. It has a number of MMI-6S2LK on it. It also says 12V DC. I
can't
> locate a direct replacement (I'm sure Sony would have it, but I bet they
would
> be expensive). MCM carries the Mabuchi replacements that are physically
the
> same size, have the same rotational direction and voltage, but I can't be
sure
> about the RPM. Is there some kind of cross reference between these two
brands,
> or is there a way to "read" the model number of the old motor?
>
Dsb3283
Wild Bill
hi.. i vaguely remember reading about replacing a cassette tape deck's
capstan motor regulator with a 3 terminal adjustable voltage regulator
circuit (an LM317 maybe).
The two internal motor leads were wired to the externally mounted VR
circuit.. a small pot is used to adjust the motor speed.
I'm not sure, but the modification may have been explained in the S.E.R.
FAQ.
http://www.repairfaq.org/REPAIR/
As Andy said, the capstans should always be rotating in opposite
directions.. your observation of the pinch rollers engaging is/are what
actually reverses the tape direction.
The drive belt should pass thru the space between the capstan pulleys
(forming an S shape of sorts).
cheers
WB
..............
Dsb3283 <dsb...@aol.com> wrote in article
<19991201234202...@ng-bj1.aol.com>...
> This deck has a bad capstan motor. The internal speed control IC (C1470)
is
> charred. If I bypass the speed control circuit and apply 12V directly to
the
> windings, the motor spins. I can't find this IC anywhere (Even the IC
Master
> doesn't list it), so the easiest solution seems to be to just replace the
motor
> with a generic (Mabuchi), but there are a couple of things I can't figure
out.
(snip, snip)
Luis Martino Ameijeiras
3845FB...@psu.edu...
> Dsb3283 wrote:
> >
> > This deck has a bad capstan motor. The internal speed control IC (C1470)
is
> > charred. If I bypass the speed control circuit and apply 12V directly to
the
> > windings, the motor spins. I can't find this IC anywhere (Even the IC
Master
> > doesn't list it), so the easiest solution seems to be to just replace
the motor
> > with a generic (Mabuchi), but there are a couple of things I can't
figure out.
I did a search in the NTE catalog, and found this:
Industry Number : UPC1470
NTE Device Number: NTE1844
IC-MOTOR SPEED REGULATOR,4-PIN SIP
Maybe this could be the IC needed. It's not the first time where a part
listed as, for example, 2SC-XXX, has only C-XXX printed on it.
Luis Martino