How to Connect Tube to Radio Capacitors
Getting your tube radio working again can be tricky, and it may take some time before you get it right. One of the first parts that you should replace is the capacitors (and it’s a good idea to replace all of them in an old radio).
Capacitors help your tube radio operate by blocking, passing, filtering and tuning all the different types of currents that it needs. There are many types of capacitors used in a radio, and the best way to know what they are is to refer to the Radio Schematic or parts list for your model.
Electrolytics
The biggest of all capacitors is the electrolytic. This type of capacitor works hard and gets worn down, causing that famous “tube radio hum”. So if you see a “humming” noise coming from your antique tube radio, it is probably an electrolytic that needs replacing.
They can be purchased new (or used) at any electronics store. Most of the time you can find them at a good discount. JustRadios carries several brand names of these caps, so check out our online catalog.
Micas
The second most common capacitor in a tube radio is the mica. These are smaller in size and have lower capacitance values than the paper and electrolytic capacitors. They are usually labeled as mfd, mmfd or MF, which stands for micromicrofarads, the short form for pF (which is equivalent to a millionth of a uF).
These capacitors also have a voltage rating on them. They can only handle a certain voltage without breaking down, so always read the schematic for your radio to determine what type of capacitors you need.
Remember that your vintage tube radio requires both DC and AC to operate. If you have a high voltage transformer, it is important to use high voltage capacitors in the circuit, so choose ones rated at 600 volts or higher.
Paper capacitors
Most tube radios were manufactured with 200, 400 and 600 volt paper capacitors. This was to save money on the manufacturing process. If you have an older tube radio, it is possible to replace all the paper capacitors with a set of film capacitors rated at 630 volts or higher. This will give your radio a much longer life span and help it to run more reliably.
JustRadios has a variety of these capacitors, so you can find the type that will work for your antique tube radio. They are inexpensive, compact and have a long shelf life.
The capacitors you need to replace in your antique tube radio are electrolytic capacitors, line filter interference suppression safety capacitors and about a dozen film capacitors. These parts should cost about $15 or less to replace.
When you replace these capacitors in your antique radio, be sure to install them with the polarity correct. If you don’t, they will not work and they could even explode.
If you want to learn more about how to restore your antique tube radio, be sure to check out our blog posts on the subject. You will find helpful information and tips on restoring your vintage radio, plus there are many great links to other related articles and web sites that can help you in your restoration project.