Mark D. Zacharias wrote:

Matthew Kirkcaldie wrote:

Hi all,

I'm trying to repair a NAD CD changer - everything works properly
except the tray motor is seriously underpowered. It tries to rotate
the disc platter but generates a pathetically small force, so that
the tray moves very slowly if at all.

I've checked everything mechanically for smooth operation, etc. The
motor is a Mabuchi FF-130SH, specs:
http://www.mabuchi-motor.co.jp/cgi-b...i?CAT_ID=ff_13
0rhsh

The player is trying to drive it in the forwards and backwards
directions by applying DC voltages, which measure about 3.9V DC and
-3.9 V DC as the player tries to spin it backwards and forwards.
In-circuit the motor resistance is about 12.5 ohm, implying it's
seeing about 0.3A (right?). So with a listed stall current around
0.5A, does that imply the player is unable to give it enough current
to move? Or is the motor resistance too high, preventing the applied
voltage from driving enough current? Sorry if these questions are
naive.

I've opened up the motor and the brushes look fine - I've cleaned the
spindle with Deoxit followed by lubrication with Pro Gold and the
motor appears to be spinning freely - it runs smoothly with no load.
However when it's reassembled the tray barely moves.

I don't have a service manual for this unit but I am wondering if this
is a commonly used motor that people may have experience with - I'm
wondering if I should source a replacement motor, or try to figure out
why the CD player isn't delivering enough current. As I say, all the
other CD player functions appear to work normally, including opening
and closing the multi-disc tray.

Any advice would be very welcome - thanks in advance for any help
someone may be able to provide.

Thanks,

Matthew.


Sometimes if it uses a belt, the belt may be too tight - this will load down
a motor. Perhaps someone replaced the belt?

Or maybe a different mech problem. A wormscrew gear may have travelled on a
shaft. This could put a load on the motor as it tries to turn the gears.
Could be a lubrication problem somewhere in there too.

I think the motor itself is probably OK. Measure the resistance again as you
slowly turn the motor shaft. The resistance will vary as you turn of course,
but will settle down when you stop. Should never vary much from the 12 or
ohms when at rest, certainly never shorted or open.

Mark Z.


Sounds to me like a cap has gone south, Are there any caps that have
vented or buffy looking. check out the power supply caps, thats the
usual cause of slow motors othe than the motor it self