On Tue, 18 May 2010 16:50:28 +0100, Arfa Daily wrote:

snip



Just another bit of info for what it is worth. The DC resistance of the
motor windings are grey to red = 4k49
grey to blue = 4k49
red to blue = 8k99
grey to motor case greater than 20Meg as read on my oldish dvm
The 220nf cap should be o/c also

Now I am curious as to what you find. If it is the motor, it might be
worth your customer getting the motor upgrade kit if it still
available. http://www.rega.co.uk/html/upgrade_kits.htm Cheers
DaveD


Thanks for the link Dave. Do you know what the reasoning was behind the
'upgrade' ? Did they have a lot of trouble with motors failing ? I would
say that this is the original motor, coming up on 25 years old. I fitted
the 3 x 47k combination, and the motor runs normally. It has plenty
enough torque to shift the heavy glass platter, and according to my
strobe disc, the speed is spot on. Voltage across the motor measured at
98v, which would seem right, given that the 47k combo comes to 15.6k
against the original value of 12k. In the circumstances, I'm prepared to
call 98v on a 110v nominal motor, a draw.

I s'pose it wouldn't be a bad idea to just check the winding resistances
before it goes back, but I don't think I'll be expecting to find a
problem, as it does run correctly, without anything catching fire.

As to why the original resistor failed, anyone's guess. About 1 1/4
turns of the spiral element have charred, right in the middle. The
resistor looks as though it has been pretty warm over its lifetime, but
again, it is nearly 25 years old, so has worked hard. Could just be that
it had started to go high and suffered a cumulative cascade failure.
Might have been a voltage thing. Some of these resistors, particularly
considering its age, are not rated especially well, working
voltage-wise. I suppose that over it's lifetime, it's had around 130v
RMS across it all the time that the motor was running. Could have been a
slight manufacturing defect such as the spiral being 'nicked', that has
degraded down the years, to the point where it became a failure. Endless
possibilities ...


I hate endless possibilities.