Restoration Commences on 1947 RCA Victor 721TCS

[Penthode]

Originally Posted by Electronic M

My Heathkit C3 tests leakage at working voltage. I can also use it to to reform capacitors. I have done a number of sets where any cap that tested as leaking got changed and ones that were good went bad after extend use. Both sets I mentioned went through that and after weeks of use and dozzens of hours of running cool the lytics eventually decided to crap out.

I've found that in the time it takes to evaluate each cap I can recap a set several times over. And the time I waste on repeated repairs on my daily driver sets when I don't do a full recap is worth more to me than the cost of capacitors or maximal originality.

Each part has a bell curve of failure and on high production sets I'm sure some examples may still be usable with all original caps today and into the future...when you find one you are winning the lottery statistically speaking....my luck usually ain't that good and I don't like to gamble my scarse time on unreliable parts after doing similar experiments to yours.

Some makes and models are more picky about exact component value than others. I've seen it for myself plenty, and some who have restored a set like yours and a Muntz will complain that the Muntz will be picky about tubes and precise (not necessarily accurate values but precise) component values.

I am not saying I do not replace electrolytics if it is not warranted. When I reform a capacitor, I check the leakage and the final capacitance. If the leakage is low at fill rated voltage and the capacitance is as rated, then I will give it a pass. In this instance I will run the set 100 hours and again measure the capacitance and leakage.

And why do you suggest I am winning the lottery? I have repaired a number of sets and about 25% have retained the electrolytics if they behave. Okay the set remains on the bench for a couple of weeks while I give it a good run though. But I am perplexed why immediately the first thing suggested to do is to replace the electrolytics without even a rudimentary examination?

The set now has completed 25 hours. I am going to investigate the video amplifier this evening and run it a few more hours.