Hickok 209A VTVM Restoration Part 4
This the fourth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 4: Restoring the battery holder.
In Part 3 of this series I documented the condition of the D Cell battery holder and outlined the restoration plan for the unit. The first step is to remove and restore the corroded battery holder.
Besides the obvious corrosion, the white connecting wire to the negative terminal was corroded under the insulation from the battery spring clip to the switch solder lug. I replaced the entire length of this wire. The other short wire and ring terminal were cleaned as described below.
The process I used to restore the battery holder:
- Desolder the two terminal wires
- Remove the holder from the VTVM
- Completely disassemble the holder
- Separate out all the metal pieces
- Remove the loose corrosion from the metal pieces using a brass brush
- Degrease the metal pieces
- Soak the metal pieces in Evapo-Rust until the rust was gone
- Treat the copper contacts with household vinegar and a brass brush to remove the corrosion product
- Remove the corrosion product from the insulator plate (phenolic?)
Once all the corrosion product was removed and neutralized I decided to prime and paint the battery clamp parts and clear coat the insulator base and spring clips (excluding the battery contact areas). I used rust primer and rust paint for the clamp and hardware and Nyalic for the insulator and battery clips. Nyalic is a clear coat product which adheres to nearly any metal or plastic and is extremely resistant to UV, acids, salts and chlorides.
The battery clamps were originally lined with cloth reinforced rubber, which I replicated using EPDM sheet material. I had EPDM sheet on hand, and it is very resistant to zinc chloride and potassium hydroxide which are common battery electrolytes. I intend to use batteries in this device.
The battery holder is restored and ready to install.
To be continued in Part 5.
Thanks for reading.