Restoration Commences on 1947 RCA Victor 721TCS

[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 init4fun

I think the bottom line here is this ;

old capacitors are kinda like old people , some live a perfectly healthy life well into their 90s and some begin to seriously degrade starting in their 60s and don't make 70 . And when those people were young there really was no telling which would see the near century mark VS who'd be worm food by 60 . I'm sure there are those caps that'll live to a ripe old age performing their capacitor duties just fine without missing a beat just as there are plenty of them that are right now going to crap in 5 year old TVs , all the while their antique counterparts are still happily doing the cap thing without a whimper . It's luck of the draw , nothing more , and while I think it's great that those particular caps reformed well and came back to life I don't believe every , or maybe even every other , antique cap can be revived in such manner . As a cool experiment I think it's great that you had success but with the destructive nature of a shorted Ecap in mind I do systematically replace every one in any "daily driver" sets I run , just so that I can feel somewhat comfortable leaving them to run while I do things in other parts of the house without having to keep a literal eye on them

I , for one , am hoping to see your experiment run well into the hundreds of hours .....

Thanks for the comment. I sort of see that as well: some have a grand old age and others sadly die prematurely.

I think the success for a long life, both in human and electrolytic terms is to recognize the symptoms of disease early and address it. Some prefer milder treatment whereas others go for radical treatment. And continuing the comparison no one know absolutely for sure if the remedy will be effective or not.

The set now appears very healthy and runs well after 50 hours in the last four days. No detectable hum, lots of clean audio and a sharp picture on my good 10BP4. And rechecking the leakage on one of the electrolytics,, it has dropped a further 80% in the last 50 hours.

Again this project is to satisfy my own personal interest in preserving as much originality in the 721TS as possible and should in no way dissuade you from replacing vintage electrolytics in your own equipment if you so desire. And if I were to leave the set unattended I would protect it by other means such as a fuse. But I am happy remain with the set while it is on.

[init4fun]

I'll easily agree that with better than 50 hours on it and the leakage continuing to drop that those caps have proven themselves at least in the short term . I really am hoping you get 100s of hours out of them because it would further your experiment and show that at least some do survive long term . I saw in your first post that you live in Canada and the set was stored in an attic . I know nothing about the general climate where you live so I'll ask , do attics there get Hell like hot in the summer like they do in the lower States of the US or is the climate cool enough there that the set wasn't subject to regular temperatures over 100 degrees (F) ? If the attic remained cool year round I'd bet that one difference likely made a world of difference in the condition of the caps VS a set stored the same amount of time in a Texas attic .

[Penthode]

I actually bought the set in central NY near Schenectady. The was no TV in Canada until 1952 and the first available TV dighna l here was from WBEN TV Buffalo NY in 1948. Muy RCA 8T243 was allegedly the first Canadian built TV manufactured in Montreal Quebec.

I bought the 721TS from the house it was purchased for and sat in for over 65 years. The attic was insulated so I guess it did not get too warm in the summer nor too cold in the winter. The set is interesting as it was quite dirty but typical he chassis was not corroded.

I bought an RCA 8T271 which included survivor electrolytics from a home just outside Philadelphia 7 years ago. The original owner bought the set just after he left the US Army with a bonus and he retained it until his death at the age of 91 in 2013. His family sold it to me and despite it not working and sitting in a corner in ther house for nearly 60 years unused, the electrolytic capacitors all came back fine and are still okay after hundreds of hours. This set, having sat indoors its whole life, had a pristine chassis. It looks like new.

So you have to take each case as it comes, I guess.

[Penthode]

The 721TS is currently running and has reached 52 hours. Running some Popeye cartoons.

I grabbed a couple of electrolytics from a rusty old Fada 630TS chassis (cabinet dissolved into shards). Looks like it was stored in a wet shed outside. So the electrolytic will have suffered wide climatic changes.

I started reforming it at 4pm today. It is now 10:30pm and at 450 volts the 10uF and 40uF capacitors in the can connected in parallel show a leakage of 200uA. This shows the capacitor is good. The 40uF measures 45uF and the 10uF measures 15uF.

I have been told I am lucky. Maybe so but I never have won a contest or even a book at the local raffle. So this baffles me why I have so much success and everyone else has horror stories to relate.

With the reformed electrolytic with such low leakage at full capacitor rated voltage, before tearing it apart, I would like to leave it at the full 450 volts for a day to see what happens. I maybe will after over voltage by say 5% to see what happens. Fortunately the failure mode is predictable: when it starts to go, like the paper capacitors, there will be a thermal runaway where the leakage increases creatingvheat which further accelerates the leakage and so on. In a paper capacitor, there is little thermal lag so the paper capacitor thermal runaway is fairly fast. The larger electrolytic thermal runaway is slower and more manageable.

Here is a picture of the reformed 630TS capacitor. Notice the VTVM reads 450 Volts DC and the Sprague TO-6 reads 200uA on the 0.6 mA full scale range. And a picture off the 721TS on the weak 10BP4.

[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.

[Electronic M]

Originally Posted by Penthode

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.

The process is simple: unsolder positive lead(s) of capacitor connect cap to Heathkit C3, check capacitance and if not open check leakage indication on tester at 50V if good select next higher range,if bad wait 2 minutes for signs of improvement if no change in reading or improvement stops change capacitor, if leakage drops to acceptible select higher voltage test range. If a capacitor tests as having acceptible leakage at full working voltage it gets ran in set for several hours and checked for temperature and possibly leakage again later.

Any more than this is well in excess of my patience, and after doing this process for a few years worth of restos I have stopped as I have come to the conclusion that it is a complete waste of my time over changing all capacitors of a type I know are prone to failure....on any chassis mount lytics once the positive is unhooked it is quicker to solder in a new part, the new parts are cheaper than the time I spend on a reforming, and the guarantee that a new production part isn't going to take out unobtainium for better than 25 years is worth more to me than original parts. I'm keeping the original tube circuits in and not shit canning them to install a flat screen and I usually keep the original removed caps in a bag with the set with a copy of the schematic and enough documentation that any future historian could analyze the original design and parts and put it back to stock if they wanted. That is as original as a working set has to be for me.

[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.

[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.

[irext]

My method for reforming electrolytics is to use a low current high voltage supply and place a 10K resistor in series with the cap being reformed. I monitor the voltage across the cap which will slowly rise if the cap is a good candidate. I'll monitor the voltage as it rises to the cap's rated voltage then remove and gently discharge the cap and reconnect to the test rig. If the cap is decent it will much more quickly charge to it's rated voltage the second and subsequent times. Interestingly if the process is stopped before the cap reaches it's rated voltage, discharged and reconnected to the rig it will quickly rise to the voltage it got to when it was disconnected and then proceed slowly to it's rated voltage, sort of behaving like a zener diode! I have a 1956 B&W PYE set I've restored and managed to reform all of the multi electrolytic cans. The set has done countless hours with these but it is only used by me. If I was restoring it for someone else I would definitely re stuff the can's. I still have a healthy disrespect of all old electrolytics.

[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.