Restoration Commences on 1947 RCA Victor 721TCS

[JohnCT]

Originally Posted by Penthode

I would also suggest you try reforming an old capacitor properly and then testing it for yourself.

I think you're assuming members of this forum haven't tried this. I won't speak for any other old timer here, but I have tried it as I mentioned in an earlier comment. What I discovered was that it was hit or miss, and therefore a waste of time when your name goes on a repair. Your example, although very interesting, won't change my experiences.

The Andrea I'm working on has a lot more hours than yours (I'd guess it's well over a hundred twenty five hours since February) and 5 of the cans are still good and operating fine, but history tells me that they're on bonus time. Using my own TV as an example, two cans were dead immediately, and two failed some 20-30 plus hours after it was running perfectly. The remaining 5 are still running fine at over a hundred hours. They're still coming out.

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

I mentioned earlier that I'm restoring an 1850s reed organ melodeon. The leather exhauster is still working, but if don't replace the leather, how long will my wife be able to play the melodeon before the leather tears? 10 hours, 100 hours? Maybe she'll never put enough hours on it, but I'm replacing the leather anyway. Once this melodeon is finished, I don't want to ever take it apart again.

That's the point we're trying to make on this subject.

John

[Electronic M]

Originally Posted by JohnCT

I think you're assuming members of this forum haven't tried this. I won't speak for any other old timer here, but I have tried it as I mentioned in an earlier comment. What I discovered was that it was hit or miss, and therefore a waste of time when your name goes on a repair. Your example, although very interesting, won't sway me at all.

The Andrea I'm working on has a lot more hours than yours (I'd guess it's well over a hundred twenty five hours since February) and 5 of the cans are still good operating fine, but history tells me that they're on bonus time. Using my own TV as an example, two cans were dead immediately, and two failed some 20-30 plus hours after it was running perfectly. The remaining 5 are still running fine at over a hundred hours. They're still coming out.

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

I mentioned earlier that I'm restoring an 1850s reed organ melodeon. The leather exhauster is still working, but if don't replace the leather, how long will my wife be able to play the melodeon before the leather tears? 10 hours, 100 hours? Maybe she'll never put enough hours on it, but I'm replacing the leather anyway. Once this melodeon is finished, I don't want to ever take it apart again.

That's the point we're trying to make on this subject.

John

+1
I've also reformed and vetted lytics with my Heathkit and watched them fail after dozzens of hours of operation.

I've seen TVs and radios run on original caps and even keep a few that way as shelf queens that rarely get powered. Though even that isn't common since if I power on a display set and it dies on me it could be an embarrassment, and even if it isn't I rather feel confident I can grab anything off my shelf and run it as if I just bought it new without worry.

I put enough hours on my sets to go through certain tubes multiple times. Anything that will help put the next repair farther out into the future and let me tackle repairing something else or let me live my life away from the bench is worth doing.

[Penthode]

Originally Posted by Electronic M

+1
I've also reformed and vetted lytics with my Heathkit and watched them fail after dozzens of hours of operation.

Well I have seen a bunch fail in service. And many have not passed the reforming process and test before putting into service. You have not explained what your criterion is. Instead you trash my observations.

And as as this to me is purely a hobby, if the component fails in service, it provides further enjoyment pulling the thing apart to service it because it is my hobby.

Maybe some of us should stop to reflect and chill out.

[Penthode]

Originally Posted by JohnCT

Sure, you can have capacitors work after 70 or more years, but proving a capacitor can work at 70 years and proving a capacitor can work for 15 hours a week for the next 10 years is another thing entirely.

John

I did mention I have a 1949 RCA 8T243 I acquired in 1970 and still runs on its original electrolytics. If I am fortunate to still be alive in 20 years, I will let you know if the capacitors are still okay.

And I generally do not watch 15 hours of TV. I the 721TS case, I simply left it running while going about other things.

I find it very amusing however how some members of this forum take the subject of electrolytic capacitor replacement so very seriously.

[Yamamaya42]

Originally Posted by Penthode

Entropic degradation? I am curious what this is.

I am amused bt your comment "when it is shown over and over again". There is a lot of stuff on the internet by many self proclaimed experts. You have not attempted to test the process and I see you are not willing to accept the evidence I has provided. The set has been on now continuously for over six hours reaching a total of 50 hours and the electrolytic capacitors remain fine.

I am not disputing anyone who chooses to replace the electrolytics. However I am disconcerted by reading here that all capacitors including electrolytic, paper and mica should be blindly replaced.

It is amusing to see defensive reaction to my hobby specific activities. I do not disagree with you if yo prefer to replace the capacitors. I have refilled many electrolytic cans myself, most recently my HP DC power supply. I am only posting this information here to demonstrate to all how the capacitors can survive more than seven decades and still work.

I am going to look inside a reformed good capacitor to see what degradation has occurred. I would also suggest you try reforming an old capacitor properly and then testing it for yourself.

I abhor the practise of applying power or even use of a Variac on a set that has not been thoroughly vetted and corrected. It is fraught with danger and because these electronic devices rely upon oscillators to generated grid bias, will lead to other component failures.

Note in this case, I reformed the capacitors and made all the required component replacements after detailed analysis of the circuit before applying full power. This set came up immediately and worked without issues.

Entropy, a product of the second law of thermodynamics, was the slow, irreversible process of breakdown and decay whereby a complex, organized system inevitably degraded into more chaotic ones.

[Tom9589]

I agree, Tom.

[AlanInSitges]

I don't get why everyone is giving OP so much grief. He's doing an experiment, it seems to be working so far, and if later that turns out not to be the case, well, lesson learned, it's a hobby and he enjoys it so...what's the big deal?

I learned something about what it means to reform electrolytics in this thread.

[init4fun]

Originally Posted by AlanInSitges

I don't get why everyone is giving OP so much grief. He's doing an experiment, it seems to be working so far, and if later that turns out not to be the case, well, lesson learned, it's a hobby and he enjoys it so...what's the big deal?

I learned something about what it means to reform electrolytics in this thread.

Hi Alan ,

I am someone , and as such , I am part of the "everyone" who has posted to this thread , and I for one have been totally supportive of his experiment .

As has been well established every case is different with regards to how well the "luck of the draw" has treated old caps and yes there are going to be the ones who reform and live on to perform their cap duties just as there will be ones that will crash & burn as in the photo* I posted in my first post to the thread . I do not believe I was giving him grief when I stated that as a fun experiment sure , I'm right with him and want to see him get 100s of hours out of his reformed caps , but my personal preference especially with daily drivers is to replace all Ecaps as a precursor to the return to daily service .


* I lifted that photo from someone's Ebay listing for an old 1960s guitar amp that was listed as "working perfectly" , and have no relation/involvement in the rectifier flambe depicted there .......

[Penthode]

I have been silent the last couple of days. I estimate the set has 75 hours and the electrolytics are fine.

I take exception to the comment Tom made. If the capacitor has sat unused for 60 years, the reforming takes hours. It is an electrolysis process you cannot hurry. In this case the capacitors as would be expected would initially test an almost dead short because in the sixty years the dielectric would have disappeared. That is why even applying a Variac is murdering the capacitors. The key is a gradual process that will take about 24 hours.

I limit the current to no more than 5mA at the start. By the time the 450v was reached, the leakage was about 200uA at full rated voltage. Then test capacity and if it is within 20% of the rated value, it is good to go. The important thing is patience.

So I dug up the crusty old space Fada 630TS clone chassis I had and removed two electrolytics. This set sat in a shed for years and the cabinet was shards. The chassis had a lot of rust and the capacitor were pretty grubby when I removed them. There appears to be a date code which suggest the capacitors were made within a week of each other in August 1947.

I put them onto the Sprague TO-6 capacitor analyser power supply to reform them. After 24 hours each of them reached filled rated voltage with a leakage current for each section below 100uA. And tested capacity and all were within 10%. I have never won a lottery and I do not think this is sheer luck. The success is patience and not using the Variac!!

I am going to punish one of these capacitors by running them at and for good measure 5 to 10% above rated maximum voltage to see if I can get it to fail. The other I will keep it at maximum rated 450 volts and then dissect it. Certainly we should not expect to see a picture similar the Banderson's which was apparently insufficiently reformed before applying normal operating voltages.

Here are the candidates. And remember, this is not one off's or luck. I am finding a consistency here.

[Kevin Kuehn]

My understanding is that the paper insulation is the weak link in saving these. Once that insulation deteriorates allowing adjacent foil layers to touch, I don't believe any level of reforming will assure a new anodized dialectic to form on the foil in those areas. I'm assuming the paper insulator material deteriorates because of contamination and exposure to atmosphere rather than improper re-forming practices(as witnessed with paper coupling caps). As far as keeping old electros healthy, I'm inclined to believe that the survivors were more likely used more often and to a later date than those that didn't make it, which likely helped maintain their dialectic layer on the aluminum foil.

[mr_rye89]

Anybody here have electrolytic caps that are >3 years old that are failing? I have a few recapped radios that started randomly humming, I'm gonna check those 'lytics tonight when I get home......

[Electronic M]

Originally Posted by Penthode

I have been silent the last couple of days. I estimate the set has 75 hours and the electrolytics are fine.

I take exception to the comment Tom made. If the capacitor has sat unused for 60 years, the reforming takes hours. It is an electrolysis process you cannot hurry. In this case the capacitors as would be expected would initially test an almost dead short because in the sixty years the dielectric would have disappeared. That is why even applying a Variac is murdering the capacitors. The key is a gradual process that will take about 24 hours.

I limit the current to no more than 5mA at the start. By the time the 450v was reached, the leakage was about 200uA at full rated voltage. Then test capacity and if it is within 20% of the rated value, it is good to go. The important thing is patience.

So I dug up the crusty old space Fada 630TS clone chassis I had and removed two electrolytics. This set sat in a shed for years and the cabinet was shards. The chassis had a lot of rust and the capacitor were pretty grubby when I removed them. There appears to be a date code which suggest the capacitors were made within a week of each other in August 1947.

I put them onto the Sprague TO-6 capacitor analyser power supply to reform them. After 24 hours each of them reached filled rated voltage with a leakage current for each section below 100uA. And tested capacity and all were within 10%. I have never won a lottery and I do not think this is sheer luck. The success is patience and not using the Variac!!

I am going to punish one of these capacitors by running them at and for good measure 5 to 10% above rated maximum voltage to see if I can get it to fail. The other I will keep it at maximum rated 450 volts and then dissect it. Certainly we should not expect to see a picture similar the Banderson's which was apparently insufficiently reformed before applying normal operating voltages.

Here are the candidates. And remember, this is not one off's or luck. I am finding a consistency here.

The ones that the leakage didn't drop fast on got replaced with new capacitors... meaning some potentially reformable caps got changed.... despite that the best of the original caps still eventually failed. If the ones that don't have measurable leakage on my C3 from the beginning are going bad then the ones that were leaking sure as hell are not going to last.

[JohnCT]

Originally Posted by Electronic M

If the ones that don't have measurable leakage on my C3 from the beginning are going bad then the ones that were leaking sure as hell are not going to last.

Back when I became a full time bench tech (70s), I was changing can caps almost daily, and these coming from TVs with a quarter of the years on them that we have now and despite having a fully formed oxide layer from daily use...

Every parts store back then had a full line of Cornell-Dubilier, Arcolytic, Mallory, or Sprague drop in cans.

NOS, used stock, reformed.. they're all time bombs - even back then when they were only a few years old. It's not a matter of if it's a matter of when.

John

[Yamamaya42]

And I said what I needed to, I will always replace ALL paper and electrolytics in anything 70s and older w/o exception, ceramic disc and mica etc are immune from this.

[Electronic M]

I'm not trying to give him grief, just replying to comments I agree with or think deserve comment. If he wants to interpret that worse than that is or get defensive that's on him.

I'm sure he likes his process being collectively admonished by most respondents as much as we like him trying to convince us we're doing it wrong...his good experiences directly contradict my experience (and those of other members I'm sure) when I tried the same approach with the same goal years ago (granted for me it was more trying to save scarse money during college than putting maximal originality first).

It's interesting reading about some approaches to reforming for some rare case where it might be preferred, but I won't be convinced my experience of vintage caps failing is wrong.