Tim Schwartz wrote in message
...
N_Cook wrote:
Does anyone know the voltages on the 3 secondaries
Main deck motor 12V but about 10.5V dc from the supply, nothing wrong
with
the ps and nothing wrong with the motor and its regulator. All that is
left
is the mains transformer.



Nigel,

For what it's worth, I'm looking at a diagram for an AD-6300U, dated
December 1976. This is a US model, with only a 120V primary. It shows
that the transformer has 3 secondaries, one of which is devoted to the
motor. It has a half wave (single diode) rectifier, D503, and a
1000uf/16V capacitor, C506. It shows the voltage on the cap as 14.5V
it also shows 2 switches, S6 and S7 in parallel between the cap and the
motor, so either switch could power up the motor. Could you have badly
corroded switch contacts that are causing a large voltage drop? What is
the voltage with the motor disconnected? If you are measuring the 10.5V
at the capacitor, then I'd say try replacing the diode and/or capacitor.

Regards,
Tim Schwartz
Bristol Electronics

Much the same, half wave, switches, cap that I repalced was 1000uF, 25V now
2000 uF. Switch contacts were the first thing I checked. No its a motor
problem and very critical on drive band properties, the main one and the
FF/REW one they both interact of course and only a narrow range of tensions
allowable. 11V in play and FF/REW now and speed constant and upto speed. I
had to convince myself it was a motor problem by connecting in 6volt ac at
the motor fuse and it made no difference because of the NEC upc1003 inside
the motor limiting current. I doubt these sorts of motors are available new
these days.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/