[Penthode]

Thought I should resurrect this old thread considering the significance of the originality of my 1947 721TS. I resuscitated this set nearly 5 1/2 years ago and this was to be an experiment to see if a fairly well preserved set could be reliably operated replacing parts only what were absolutely necessary.

In the resuscitation of this set, it retains all but two of it's carbon resistors. About 95% of the paper dielectric capacitors were changed. The ones that were retained were shunted by resistances which swamped the leakage resistance of the capacitors. It retains some of its original tubes. I carefully selected RCA period tube for replacement so it is a fully RCA tubed set. When I received the set 10 years ago, it had sat in a heated attic in a house near Schenectady for just over 50 years. Upon pulling it apart I found a small mouse nest under the chassis and fortunately it caused almost no damage. The set was not powered from the early 1960's until after it's resuscitation in 2020.

However, of major consideration is this set retains all of it's original electrolytic capacitors. This thread describes the extra effort I took to preserve the capacitors. I am not averse to changing the electrolytic ic they test bad. But slowly reforming the dielectric on each electrolytic in this set brought them all back with very low leakage.

So the bet was on as to how long they would last? I power the set on average once a week and let it run for a couple of hours. I decided to check the capacitors this evening and can report that they all appear fine.

Here after 5 1/2 years, after the careful reforming of all the original electrolytic cans, are some off air shots. (I did replace the original 40uF axial lead electrolytic but all the chassis mounted cans are now 78 years old.