I have an old Philips CRO which is not working.

I think this is a 1940s vintage item.

I opened it up and one of the Aerovox 4Mfd 600V capacitors has failed. I am having trouble locating an equivalent 600V capacitor.I was wondering if someone could point me in the right direction for replacements. I tried RS, Farnell etc with no luck.

I was planning to replace all the capacitors.

Thanks

Andrew

600v is hard, if not impossible, to find here these days.

You could try Mouser in the USA:

http://au.mouser.com/.

You could put two identical 8mfd caps in series which would make 4mfd. The voltage rating of the individual caps would need at least to exceed half of 600V. Preferably 600V in case of a short in one of them.

You would also need an identical resistor in parallel with each cap to balance the voltage between them. I am not sure of the value of the resistor - hopefully someone will know.

Is there a problem using a 630V one in this instance?

Nothing but availability I suppose.

I tried the series ideas years ago on the work bench but without the resistors until I picked up a 630V cap. But you need to watch the voltage where the two caps join as the set warms up, especially if they are not known good caps. If it looks like exceeding the voltage rating of the individual caps, turn off quick!

If the rectifier valve is directly heated, substitution with a compatible indirectly heated valve should reduce the voltage stress on the caps.

My Heathkit OS 1 has a 730V+ rail. I would get two 450V 8mfd (EVATCO) put them in series and get two 470K HV resistors TV) and put them across the caps (as they did in Heatkit). 1:1 voltage divider: half the volts across both.

Marc