Rebuilding Mershon Wet-Electrolytic Capacitors

Rebuilding Mershon Wet-Electrolytic Capacitors

Excerpted from postings on The Antique Radio Forums, Jan, 2006
by Bill “Exray” Meacham
Vieques, PR, USA

Mershon Wet-Electrolytic Capacitors

(Stud Mounting, Copper Container)
Capacity Mfd. Operating Voltage, DC Philco Part Number
6 400 4916
8 400 6706
10 475 6893
12 400 4818
14 400 5725 (25-cycle sets)


Get a screwdriver under the edge and tap all around the seam between the shell and cap. It will pop off. Don’t heat it unless it is bone dry inside. Don’t ask me how I learned that! Here’s what I did after removing the cap.

Here’s the corrosion I found underneath the cap.
There’s a washer and rubber seal here that had to be pried loose.
I used an old pair of linesman pliers to ream out the hole.
Long nose pliers to wind up and dig out the old innards.
After cleaning the copper shell of corrosion and tarnish, I added a wire extension onto the positive end of the new cap and insulated the lead to reach the center terminal on the bottom.
Drill a hole in the lip and pre-tin the area around the hole to accommodate the negative lead from the cap.
Here is the cap soldered into place. Replace the copper cap. Be sure the soldered area does not interfere with the top cap sliding back onto the shell.
A hole is drilled in the base insulator for the new positive wire to pass through. It can be attached to a solder lug along with the other wires of the circuit.
Top cap is finally re-fitted. Completed cap, ready for installation!