Restoration Commences on 1947 RCA Victor 721TCS

[JohnCT]

Originally Posted by Penthode

The 721TS has been running for about an hour this morning. I am told the electrolytics will not last long term. I am curious what evidence is there of that?

If it's going to be a shelf queen and get run for 10 minutes several times a year, you may not have a problem.

I restored a 51 TV earlier this year and did it one part at a time just to bone up on tube troubleshooting. Once done, it was shotgunned (well, not fully done).

This TV has nine electro cans, and two were bad on first power up, one taking out the 5U4, the other taking out a 6X4. I pulled them and restuffed them, and soldiered on.

While working on the sound section, another can that had previously checked fine and had run cool for several hours decided to make itself known. A slight change in the picture followed by a hiss told me another can had enough. Where it was running cool for several hours beforehand, it now was *very* hot. The fact that it was also drooling like a 5 year old kid with a mouth full of Sour Gummy Worms was another clue..

So far, 4 cans restuffed and the other 5 will be done before final assembly. The paper caps that are running fine will also be replaced before final assembly and alignment.

John

[Penthode]

Originally Posted by JohnCT

If it's going to be a shelf queen and get run for 10 minutes several times a year, you may not have a problem.

I restored a 51 TV earlier this year and did it one part at a time just to bone up on tube troubleshooting. Once done, it was shotgunned (well, not fully done).

This TV has nine electro cans, and two were bad on first power up, one taking out the 5U4, the other taking out a 6X4. I pulled them and restuffed them, and soldiered on.

While working on the sound section, another can that had previously checked fine and had run cool for several hours decided to make itself known. A slight change in the picture followed by a hiss told me another can had enough. Where it was running cool for several hours beforehand, it now was *very* hot. The fact that it was also drooling like a 5 year old kid with a mouth full of Sour Gummy Worms was another clue..

So far, 4 cans restuffed and the other 5 will be done before final assembly. The paper caps that are running fine will also be replaced before final assembly and alignment.

John

I have running four other RCA sets from the late 40's. Two 8T243's (I sold one) an 8TC271 and a 9TC275. The 8T243s and the 9TC271 were dormant and never plugged in and I simply reformed the capacitors and use them regularly with no problem. I have had the 8T243 for 50 years this year (yep I was given it in 1970. I have used it for 50 years since on its original electrolytics. The 9TC275 on the other hand sat in a damp basement and the seller pugged it in until he said he saw smoke. I looked at the electrolytics and two cans were ruined and a third survived. I have a CTC5N color and it has all the original electrolytics. A CTC11 with high hours had bad electrolytics and i ended up replacing them all.

The 721TS I plan to keep and I want to retain as much of t original as possible. And my past reference is more than 50 years of restoring electronic equipment. I see that the Sprague and Mallory capacitors have an unduly bad reputation.

If the electrolytics lasts 100 hours and I do not abuse it I expect it will last the remainder of my lifetime. Would you agree? I would also venture it will outlast a modern replacement if I was to install one.

The 721TS has been running 20 hours now and still running fine...

[JohnCT]

Originally Posted by Penthode

If the electrolytics lasts 100 hours and I do not abuse it I expect it will last the remainder of my lifetime. Would you agree?

I have no way of knowing how long the caps might last or how often you will run it. It may go 100 hours, it may go 20, or it may go boom the next time you try it...

Anything I restore I do so with the expectation that the next guy won't have a lot to do if something inevitably fails - and that guy will be one of my two sons in most cases.

I have two items of significant age running original capacitors: one of my Fisher X-1000 integrated tube amps from 1962 has all it's original capacitors - my original X-1000 blew a can about 35 years ago. In any case, I don't let either Fisher run unless I'm in the same room with it.

The second is my 1929 RCA Radiola 62. This has no electrolytics at all and the paper capacitors are made with rice paper instead of rag. Radiola experts say don't change any caps in a 20s Radiola unless you run across one.

I would also venture it will outlast a modern replacement if I was to install one.

No chance. Go to DigiKey and order Panasonic low ESR, high pulse caps. These will outlive you and I combined.

The 721TS has been running 20 hours now and still running fine...

I used to do monitor work for an arcade operator many years ago, and he would say that you're on bonus time...

Parting shot: when I restuffed the four cans on my TV, I did a postmortem on the innards and what I found is a lot of degradation in the foil and the paper as I unrolled it. It wasn't a matter of if it was a matter of when. The other five cans in my TV are still original and of the same manufacture, but I know what's inside and I know they need to be serviced before they burn out a part that could only be sourced from the nation of Unobtanium.

John