Restoration Commences on 1947 RCA Victor 721TCS

[Penthode]

I want to emphasize that I never power up electronic equipment of this age without first doing a full electronic assessment. As with the RCA 721TS, I assessed each electrolytic individually by isolating each electrolytic and reforming the dielectric.

I apply a power supply current limited to 10mA maximum and wait until the full rated voltage is met with less than 1 mA leakage. I typically aim for less than 500 uA. If the leakage after a day or so is 1 mA or higher, the capacitor will be replaced/ restuffed.

The 721TS electrolytics all showed leakage well under 500 uA at full rated voltage and tested correct capacity within 10%. I will say that surprised me. But with my six RCA TVs from the late 40's, I have only had to restuff/ replace three electrolytic cans in total.

The problem is suddenly powering them up after a long dormant period without reforming will place undue stress. But I would be game to monitor current leakage over say a week of full rated voltage to see if they survive and if so, I would not hesitate in leaving them in place.

My 721TS has been running on the capacitors for two years now with no sign of failing despite warnings from others.