Old "cm" label conversion. 1cm = 1.1pf See: http://www.radiomuseum.org/forum/old_capacitor_markings.html
For an example of different capacitor types see this page.
One of the first steps to a proper vintage tube radio restoration is replacement of old capacitors. Typically the wax/paper and the electrolytic are "Shot-gunned" or wholesale replaced prior to any other troubleshooting or further restoration. The old capacitors can be clipped out and new ones installed. Or Re-stuffed.
Re-stuffing a capacitor is the process of putting new internal components into the original capacitor shell. Most typically this is done to the electrolytic can capacitors that are mounted to the top side of the chassis. Most times the electrolytic capacitors are simply disconnected and abandoned in place. New capacitors are installed under side of the chassis, out of site.
The original wax/paper capacitors may also be re-stuffed for a "Museum" quality restoration. This is a very time consuming process usually reserved for the most precious of radios. Most Wax/paper capacitors will never be seen unless the chassis is removed from the cabinet and flipped over.
When there is no space under the chassis for new electrolytic capacitors the original can may be "re-stuffed" with the new replacement capacitors. These pictures below of a Zenith Transoceanic electrolytic capacitor showing the steps on how it is done.
On Chassis - Twist Lock can capacitor restuffing.
Stud can capacitors. (not restuffed)
Here is detail of a Philco capacitor. The internal plates have been removed with a long needle nosed pliers. The post was reinstalled with epoxy to be used as a binding post. This makes a convenient place to solder an external capacitor.
Re-stuffing a capacitor is debatable when the conditions of; A) There is plenty of room under chassis and B) The other replacement capacitors have not been hidden (re-stuffed) with in the original wax/paper capacitor wrapper.
On the chassis - Can capacitor replacement (not restuffed).
A terminal strip is used to mount the new capacitors and provide a convenient place to hook up wires.
Emud filter capacitor resuffing.
From this radio click here. This dual cap is rated at 350 volts. Two of the 47uf 450 volt caps from Mouser fit.
Replace the cover with hot melt glue and bolt back in the chassis.
1923 Grebe Syncrophase bypass condenser (capacitor).
A little hot melt glue will adequately seal up these capacitors. The tin exterior not shown is receiving a sprits of gloss black and a shellac top coat. I will save the original internals in case an owner would like a 1920's cap.
European Radio capacitor types.
Another article about US resistor with pictures with a few European.
If you hear a rushing, crackling or thunder storm coming from you speaker regardless of what band or frequency you tune to. The volume typically quiets the noise when you turn the volume down. Follow this hyperlink.
Another link for caps http://oldradio.ca:83/Radio/CapRestuff/restuff.html
I built this ESR accessory (from http://octopus.freeyellow.com/esr.html) to be used with an oscilloscope and a generator. It uses two resistor, three BNC connectors and one container. I did add a switch with a 10 ohm and 1 ohm resistor across the capacitor lead connector. This is used to set up the oscilloscope.
I have little call for retention of original capacitors. However I also work on Ham Radio gear of relatively young age. This gear does not always call for shot-gun replacement of capacitors. Another example is a Ten Tec 12vdc 18 amp regulated power supply (not shown). It contains a 26,000 uf capacitor. I prefer to keep this capacitor if it measures low ESR and good capacitance.
I just do not see the need for a $150 digital ESR meter. This adaptor does fine for my infrequent need to check ESR. I may make one of the complete analogue units from the links above. I can see how handy a portable ESR meter can be.
I want to add a plastic overlay on the CRT, on which I will create a resistance gratitude. Until then I will use the ESR Adaptor set-up switch in combination with the scope's vertical gain and position.
Normally all electrolytic capacitors are replaced for a radio restoration. An ESR tester and the subsequent retention of original capacitors applies to fairly young equipment that has been in regular operation. I do NOT keep old capacitors in restored vintage chassis.
There are particular capacitors that are connected from the chassis to one or both of the power lines (mains). These capacitors are typically called RF bypass capacitors. They shunt signals that would interfere with the proper operation of the radio. They also provide an RF ground point for the antenna system of the radio.
See Just Radios for the ABC's of Safety Capacitors.
Reforming a capacitor
This is a nice procedure that explains reforming a capacitor. You may have a nice clean old 8uf 1000volt oil filled high grade modulation B+ supply capacitor from a Johnston Valliant II that you do not want to replace. There were no leaks, the low voltage cap meter shows good micro farads. And the ESR tested good. So using a good and proper reforming process should work.
The Valliant capacitor responded as though it did not need reforming, But I wanted to run it up the working voltage before trusting it in the chassis. I will have pictures later of the test set up I used.
As a rule I generally do not reform capacitors.
Consider your self to be an Audiophile? Then you should read this capacitor article:
Keep reading about testing capacitors with:
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