electrolytic capacitor replacement question

[kb12]

Hello all,

I just bought my first tube radio - a cheap Sylvania AM, probably from the late 60s. I dont know much about radio electronics but want to learn. I turned it on and the stations came in clear but there was a loud hum. A bit of searching and I have come to the conclusion that it is the electrolytic capacitor that needs replacing. I found the capacitor and on it there reads 40-60, 20-40 and 10-20. What new replacement capacitors should I look for to replace this old one? Too high of voltage is better than too low right? What do the ranges mean? Thanks for any help you can give!

[bandersen]

Usually, it's capacitance - voltage. So you have 40 uF @ 60 volts, 20 uF @ 40 volts and 10 uF @ 20 volts. Yes, going higher than the specified voltage is fine. Too low and it's likely to fail.

On the other hand, those could be capacitance ranges. I've seen some replacement caps marker like that where they indicate the original values it can replace. In that case I'd try to find a schematic to be sure of the correct values to use. If you can't find a schematic, maybe split the difference and use 47uF, 33 uF and 16uF caps ?

[jr_tech]

I don't get it then... if it is a typical aa5 tube radio, the power supply should be on the order of 100 volts or more... usually the caps would have a 150v rating. A common 3 section cap in such a receiver would be something like 40uf/150v, 30uf/150v with either a 3rd section rated at 150v for the power supply or with a lower voltage rating if used as cathode bypass of the output tube (like 50uf/25v). A peek at a schematic is needed here.
jr

[leadlike]

I had similar multisection caps that gave ranges and not voltages. Really confused me the first time I saw it (a generic replacement in a Transoceanic). Possibly this is a replacement can in the OP's radio as well-I just can't see a trusted manufacturer willing to put something in with such wacky tolerances, but a repairman needing a part with some serious leg room for tolerances would certainly need these.

Typically, the voltages for these caps would be something like: 47@150v, 33@150v, and 10 at 25v (although this could also be 150v as well).

At any rate, do not run this radio until you replace this bit! You will trash much more expensive components if you do. Also, if the hum is coming from that capacitor can, the hum should be present no matter how high or low you tunr the volume control. Hope this helps.