Need recapping tube radio advice

[gto127]

Getting ready to recap 30's car radio for someone. I realize you can replace old paper types with modern poly but is it spec for spec or should I go up in voltage to be safe since poly type can short?

 

[rayma]

Getting ready to recap 30's car radio for someone. I realize you can replace old paper types with modern poly
but is it spec for spec or should I go up in voltage to be safe since poly type can short?

You should have no trouble upping the voltage substantially for the same capacitance and case size.

 

[gto127]

So it would be advisable to do so?

 

[rayma]

So it would be advisable to do so?

Sure, that's fine for film types. Electrolytic types should be used at half the rated voltage or more, though.
The Sprague 715P "orange drop" series is very rugged and good quality.

 

[gto127]

I did run into a problem replacing electrolytics on tubes one time-I think type I used were not high enough current. I will try srague 715p. So if circuit put out 50v you should use 100v lytic?

 

[rayma]

I did run into a problem replacing electrolytics on tubes one time-I think type I used were not high enough current.
I will try srague 715p. So if circuit put out 50v you should use 100v lytic?

The Vishay/Sprague 715P are film caps, and so are good for smaller capacitance values, around 1uF or less.
If you need electrolytics, use high ripple current, 105C rated caps for this, at around 3/4 of their rated voltage.
For example, if the circuit has 50VDC, use 75V-80V rated electrolytic caps.

 

[gto127]

Thanks for information Rayma. I will give those a try.

 

[DF96]

Don't be tempted to 'recap' the RF parts unless you know what you are doing, and can reliably distinguish between a decoupling cap (which can be replaced, if necessary) and a tuning cap (only replace if faulty and you know how to re-align). Elsewhere, replace only one or two components at a time then retest to make sure it still works. Check resistors too, and replace any which are more than about 50% off value.

 

[gto127]

Thanks DF96. The more I look at this I'm considering to send to a specialist. Many of caps/resistors are faded beyond recognition. service manual has 20 caps in here but only 14 are obvious caps. Anyone know a good tube radio repair center in U.S.?