High voltage capacitors

[Retropin]

Question for the electronic gurus..

I have a RC circuit at 100VAC. Resistor and cap are in series and used to adjust the frequency of a dual magnetic 100V motor. Im not sure what the resistor value is as I need my wifes glasses and she aint sharing them right at the moment, but the capacitors are 400V .01uf electrolytic. Motor runs smooth for a very small distance of travel, then gets very juddery and sometimes just stops completely. The mechanism it moves is free moving on its own.. no drag etc. Motor is juddery and staggers when powered with nothing attached.
Before I go trying to find new motors ( the most difficult part to source) ill try replacing caps and resistor.
But heres the question.. can I replace an electrolytic with say a polyester or green cap? ( seeing as .01uf 400v electrolytic aren't immediately available)

[Steevsee]

Hi Gav.
Found this info on diyaudio site.

"Replacing electrolytics with polyesters is normally fine. Polyester caps are way better than electrolytics in the same value. Polycarbonate are better, Polypropylene and Polystyrene are better still. "

[Retropin]

Thanks Steve,
I was researching a bit myself also as it struck me odd that a polarised cap would be used on an AC circuit.
Heres the cct on the far right..." Up down flight motor"



The 0.37uf is a polypropolene cap .
Don't really understand this little cct.. im wondering if using electrolytics like this puts a reverse bias across the motor so only one side of the motors windings is active at any given time?

[Marty Machine]

Is it definately A.C driving the motor?

Sorry, i can't see whee the voltages come from, beyond that 4-pin connector on the left side of schematic....

To me, it looks like a typical DC driven motor-switching arrangement, the electro's probably used for de-glitching the relay contacts during changeover etc...

You might find 1 cap is open, or even low impedance causing your 'shuddering' problem.

Anyway, changing the caps is a good start, easier than finding that motor :-)
A modern .01uf 630v greencap will be fine.

MM.

[Retropin]

Thanks Marty..

Voltage is from the bottom rail and powers all the motors and the blue light.. it goes to the transformer on far left which has a 100V output..

.. just to add, the relays are 250V 5A micro switches