Re-stuff Vintage Electrolytic Capacitors

In a recent repair, I experienced an issue where one of the main electrolytic capacitors in the radio had gone faulty. The radio was an Ultra Electric R506 circa 1945, and the capacitor was an old style can capacitor that had two capacitors in the one can. The can capacitor used the outside chassis as the common of the two capacitors (notice the red mark on the base of the capacitor that indicates one of the values of the capacitor).

As you can see from the marking this capacitor has two values, a 16uf and a 24uf capacitor (the 16uf capacitor is on the terminal with the red indicator).

While testing the part, I identified that one of the capacitors in the can had a value of 22.5uf, when it should have read 24uf. When I tested the capacitor for leakage, it was, so this will need to be replaced. 

The second capacitor in the can had a value of 7uf, where it should have had a value of 16uf. It was also leaking badly, so that capacitor will need to be replaced. 

I could have installed two new capacitors on the underside of the chassis and disconnected the terminals from the old can. While this would have worked it would not have looked professional. My other option was to re-stuff the capacitor can with two new capacitors (modern capacitors are smaller and should fit in the old style can).

I prised open the metal seal covering the terminal block, by inserting a small flat edge under the metal lip, and slowly working the way around the top of the capacitor. If you take your time with this step, you should be able to open the capacitor without tearing the metal of the seal.

Once opened, the next step was to disassemble the old capacitor and remove the old electrolyte and plates from the can. Once this was completed the next step was to prepare the old terminals for new capacitors I would install. I drilled out the rivets for the old terminals and disposed of these.

Following on from this, I built up the new terminal which was going  to mount the new capacitors and connections (for the capacitor). This new terminal was constructed from an M3 nut and bolt with a couple of solder tags, flat washers and a lock washer.

Once the old electrolytic capacitor was cleaned, a nut and bolt was used to attach a solder tag onto the inside of the capacitor. A wire was soldered to the solder tag that would then be connected to the common (negative) of the two new capacitors.

As 24uf capacitors are not a standard value, a 22uf/350V capacitor was used for the 25uf capacitor. A new 16uf/350V capacitor was used as a direct replacement for the old 16uf capacitor (both capacitors where high temperature 105 degree C variants).

In the above image you can see that the common (negative) of the two capacitors is connected to the wire/solder tag fitted inside the capacitor can.

Each of the positive leads of the two new electrolytic capacitors,  were soldered to the solder tags on the terminal block (note that the solder tag is on the outside of the terminal block to make it easier to connect the wires in the radio back to the capacitor).

Each of the terminals were colour coded to make it easier to identify the value of the terminals. The Blue terminal is the 22uf Capacitor, while the Red terminal is the 16uf Capacitor.

The terminal block was refitted into the capacitor can and the capacitor can was closed by slowly pushing the side walls in over the terminal block (as shown above). This was a slow process, as I did not want any creases in the metal (which tend to be problematic to remove).

Once the seal was closed over the terminal block, the capacitor was tested and then re-installed back into the radio.

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