My girlfriend picked up an old Philco tabletop AM radio. If I had to guess, I'd say it was manufactured around 1960. I couldn't find any model number or year stamp. It's encased in plastic. It powered up, but didn't really pick up any signal. I told her that I'd open it up, clean it up and inspect for any bad parts.


The tubes looked in good shape, but there was a cap that is blown. I'd like some reassurance that it is indeed a capacitor and that my reading of the color code is correct.

Pic of Cap

I read it as yellow, violet, orange, black, yellow. According to an online calculator, that gives me a \$4.7 \mu F, \pm 20\%, 400V\$ cap. Does that seem correct? If so, what is a suitable replacement? Searching Mouser or Digikey yields many results. I'm not sure which part is best to go with.

  • \$\begingroup\$ Don't be tempted to use a PC scope (or even a regular one) unless you are pretty sure you have attenuated and isolated any higher voltages you might probe, occasionally some budget radios would skimp on the supply transformer and rectify mains directly leaving parts of the circuit live. \$\endgroup\$
    – KalleMP
    Commented Nov 1, 2015 at 23:35
  • \$\begingroup\$ I have seen this type of cap on Studebaker Philco 1956 6V car radios .Yes it is 47n. \$\endgroup\$
    – Autistic
    Commented Jul 31, 2016 at 3:32

1 Answer 1


I read it as 47000 pF which would be 0.047 μF. That's a pretty common value in tube type equipment.

Yes, a 400V rating is reasonable.

You should also check the power supply filter cap. That is the tall round can. It most likely has either 2 or 3 sections internally, each with its own connection. The can is the common negative terminal.

  • 2
    \$\begingroup\$ +1 this. If you're going to replace some of the capacitors, replace all of them. It's a safe bet that the rest are either bad, or going bad, and at the minimum their value has probably drifted considerably. \$\endgroup\$ Commented Jun 20, 2015 at 17:20
  • \$\begingroup\$ Also, if you still have problems, you need to find a tube checker for the tubes. Just because they look OK, that is no guarantee that they are OK. \$\endgroup\$ Commented Jun 20, 2015 at 21:44

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