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 Post subject: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 1:52 am 
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I would like to try restoring some old 01A tubes that test low but still have good filaments. I have a few candidates and have done some reading about how it's done and I wanted some advice from the pro's out there who have already performed this procedure. My questions are:

1. What voltage to use for restoring?
2. Can I alligator to a battery eliminator as the power source or do I need some other device?
3. How often do I stop to check the tube?

As always, any help to further my education is appreciated. :)

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(Member - Michigan Antique Radio Club)


Last edited by atwaterkent1 on Feb Sat 24, 2018 3:31 am, edited 1 time in total.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 2:05 am 
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Dan

I use a tube tester and set filament to 6.3 volts or a little higher by increasing line voltage. Leave the tube bake in without plate voltage. (Do not push any test button)

After a few minutes test the tube with 5 volts on filament. See if there is any recovery. You will find some tubes recover in 5 minutes, others can take an hour or more. I find RCA & Cunningham, made by the same company, usually recover well.

There are procedures suggesting very high filament voltage. I wouldn't go much above 7 volts.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 3:33 am 
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Got it Norm. Will give it a try tomorrow. Thanks for help.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 4:21 am 
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Dan,

Radio fans of the 20's would rejeuvenate without any extra equipment by using the radio. FWIR on brand of radio recommends the method in their instructions.

This would apply to any radio that has just rheostats to control the filament voltage and no other filament dropping resistors like are found in A-K or any set having Amperites.

Remove all B+ connections from the radio, unplug all headphones and speakers. That should open the plate circuit to all tubes. Turn on the radio and turn up the rheostats so there is no resistance and the tubes are receiving 6 to 6.6 volts Let the tubes burn for 1/2 an hour. If the tubes still have some life there will be recovery of the emission. If the tube(s) did not increase emission you can make adapters for a tube tester.

Follow these instructions for further rejuvenation. The first level is a greater level of filament burn. The fila level is the flashing/aging.

http://www.nostalgiaair.org/References/ ... lash08.htm

In ALL incidences of advanced rejuvenation be sure there is NO connection to the plate and grid. Such a connection at the high level if filament voltage would immediately strip the filament of surface thorium. If allowed to remain any time could completely exhaust the supply of thorium within the filament.

I use both a UX/V adapter made from a surface mount bayonet tube socket and an interposer that plugs into the tube tester 4-pin socket and couples to a four pin socket connecting only the filament pins. The use of adapters avoids accidental shorts with alligator clips that could destroy the filament emission. The surface socket will accept a UV-99 adapter for test and rejuvenating.

Interposer: Plug on one end, socket on the other, only filament connected. Yep Amphnol ring mount 4-pin will fit a EMT coupling, no filing.
Image

Surface bayonet socket with Amphnol plug
Image

Frost UX to UV adapter, fits into the bayonet socket.
Image

Here is a 200 in the socket without the interposer in between.
Image

GL

Chas

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 3:16 pm 
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Look closely at the filaments when they are lit at normal voltage. If they are noticeably brighter than modern tubes, the filaments are thoriated tungsten and there’s a chance rejuvenation will work if it hasn’t already been done once or twice in the past. But if the filaments are about the same color and brightness as those in more recent tubes, they are oxide coated. In that case they cannot be rejuvenated and may in fact be made worse by attempting it.

The 01A was in production for a lot of years—from about 1924 until about 1940–and only the early 201A and 301A types actually had thoriated tungsten filaments. Oxide coated filaments were more efficient for receiving tubes and cheaper to make, so they quickly displaced the earlier materials even in types like the 01A. If your 01As have ST (shouldered) bulbs you can be almost certain that the filaments are oxide, since that bulb style didn’t come into use until 1932.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 6:02 pm 
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I have rejuvenated ST 01's. In my many years as a tube collector and member of TCA, I know of no discussion that would lead me to suspect that ST 01a's have an oxide filament. That said, if the tube is flat it makes no difference if it dies in rejuvenation, it was useless to begin with, now a confirmed socket filler. At least for those radios that look good with ST's. I have but one radio that displays ST's well, a Splitdorf Abbey, its inner panel covers all the sins below deck and exposes the tubes at the last inch or so. Most "S" bulb 201a's are heavily flashed therefore look rather badly above the polished deck. The ST's are clear and proudly lite... I do NOT know if a 201B, 'BB, 'C have an oxide filament. I have no knowledge of what type of filament is in the many DeForest versions. I can say the DV-3 is oxide.

There are a few of early tubes, maybe more, that transitioned from thoriated to oxide, The 210 can be found etched as both thoriated and oxide, The 71 was thoriated then became the 71a in oxide. Check the table in the Nostalgia Air article...

The 216 FWIR was also thoriated replaced as an oxide 81 as was an early 80 design, type number I have forgotten, seldom seen and lesser so of the equipment that used it.

There are other rejuvenation tables that include a few obscure types that can be rejuvenated. Almost all have very similar flashing, aging times and voltages.

There is at least one commercial rejuvenator for the radio fan of the 20's, the Jefferson.

http://www.roger-russell.com/jeffers/jeftest.htm

For many years I had a Radiola 28/104 within the power unit with has wicker sides and back. I kept a thoriated 210 in it :)

http://www.antiqueradios.com/forums/vie ... hp?t=93514

YMMV

Chas

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 7:35 pm 
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01AA is the oxide filament version of 01A. Not all oxide filament tubes were marked that way.

https://www.radiomuseum.org/tubes/tube_01aa.html

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 7:58 pm 
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I have three Radiotron, brass based, tipped tubes with good filaments and one beautiful looking DeForest that has a good filament but tests at 2, just a little under the 455 range a good one should test at. I plan to get to them tomorrow. Just purchased a DC power supply from Don in the classifieds, later when I get time I plan to mount a tube socket on a board along with a timer and use it for future rejuvenation.

Thanks everyone for all the good info. As a newbie I am grateful for all of you who take the time to help me out. Over time as I gain experience I hope to be asking fewer questions and answering more for others. Thanks again!!

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sat 24, 2018 8:30 pm 
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If the tubes are working satisfactorily in your radio I wouldn't rejuvenate them. Some tubes do not respond very well and may end up being worse.

Dave


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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sun 25, 2018 1:56 am 
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Hi Dave,
I test all the tubes before they go into any radio and test any that come with the radio before I power it up. By doing that, if there is a problem with a new radio, at least I know it's not the tubes. I would rejuvenate only tubes that fall significantly below spec. I want each radio to perform the best it can.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sun 25, 2018 6:20 am 
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These tubes are a little different than more modern types. Volume is controlled by adjusting filament voltage. Even a weak 01A may give good performance with filament rheostat turned up a little.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sun 25, 2018 2:26 pm 
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On a historical note, RCA tubes in the 1920s were developed and manufactured by either GE or Westinghouse, beginning with the latter's WD-11 in 1921. It had an oxide coated filament. As the story goes, thoriated tungsten was an accidental discovery at the GE lamp works in Harrison, NJ, when some tungsten wire with trace amounts of thoria was used by mistake in some UV-201's at the factory, and they found that at half the filament voltage normally used, it produced about 50 times the electron emission of pure tungsten. Thoriated tungsten filaments first appeared in tubes for general use with the UV-199 and UV-201A which first appeared in late 1922. GE stuck with thoriated tungsten in all of the DC filament tubes they did for RCA up to the 222, which was designed in 1924 but didn't make it to the public until 1927. Westinghouse saw no reason to change what it was doing, so most their DC filament tubes have oxide coated filaments. From 1925 on, RCA shifted the focus to AC tubes.

Although RCA tried hard to control the manufacture of tubes by others, they could not always do so. Loopholes in patent law made it possible for some independent manufacturers to survive. Others simply set up shop and made tubes until RCA shut them down. Later on, RCA found it easier to license others to make certain tubes than chasing them down and dragging them to court. So if you have a genuine RCA/GE UV or UX 201A, chances are that it has a thoriated tungsten filament and rejuvenation may be possible. But if it is some other brand, it's anybody's guess what kind of filament they used. It may be thoriated tungsten or it may be something else.

One word of caution: rejuventating filaments calls for heating them well above their normal operating temperature briefly to "boil off" the depleted layer at the surface of the filament and expose new thorium. If the procedure is continued too long, it is possible to de-activate the filament by removing too much thorium. Problem is, with an old, used tube, you do not know how much thorium is left or how much time it should sit on the rejuvenator (or tube tester). This is also why the process usually only works a couple of times, then the tube is dead and cannot be brought back to life. There are a number of different recipes in books and online; you "pays your money and you takes your chances"--then maybe you pays your money again. My advice is to never attempt rejuvenating a tube that is still operating satisfactorily now, as it might not be when you're finished. Only try it on tubes that have so little emission left, they're only good for display duds anyway.

It might also be noted that there were "gadgets" and gimmicks that claimed to be able to rejuvenate oxide cathodes and filaments. Most of them also worked by operating the tube briefly at higher filament voltages, sometimes with plate voltage applied, sometimes without. The idea was to disrupt the surface of the cathode somewhat and expose new oxide material. It actually does work in a few cases, but usually only a tiny amount of new oxide material is exposed and it soon burns out. If you are lucky the tube works for maybe a few more hours or a day or two, then it becomes weak again. It is also possible to disrupt or damage the last bits of active material, turning a weak tube into a dead one, so you don't want to try it on any tube that still has any chance of working as it is.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sun 25, 2018 10:21 pm 
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Thanks for the history lesson Chris, I was wondering about the Westinghouse and GE labels on RCA tubes.

The rejuvenation process worked on all three tubes. I was especially pleased to bring the DeForest back to life. Thank you all for the help, it's greatly appreciated.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Sun 25, 2018 11:33 pm 
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Dan,

Your very welcome!

I would have given the A-K tube a 50/50 chance, I was unsure if it was a thoriated filament.

If you would like to stay on top of tube history and all its nuances, consider joining the TCA, Tube Collectors Association.

http://www.tubecollectors.org/

Chas

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Feb Mon 26, 2018 12:46 am 
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I'll check into it! Thanks.

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Mar Sat 03, 2018 5:06 pm 
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I have used this device and it works well. Unfortunately, the meter is bad.

Jeff
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 Post subject: Re: Rejuvenating 01A's
PostPosted: Mar Sat 03, 2018 10:13 pm 
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That's a good looking piece of hardware Jeff.

I've had some good results, eight out of ten tubes responded to the rejuvenation process. Can't complain about that! :D

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 Post subject: Re: Rejuvenating 01A's
PostPosted: Mar Sun 04, 2018 11:05 pm 
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It is one of the few things that I bought as “new in box” that actually was, new in box including the instructions. The meter worked once then went open circuit. May take it apart to fix one day.


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 Post subject: Re: Rejuvenating 01A's
PostPosted: Mar Mon 05, 2018 3:51 am 
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I just finished a run of 9 out of 11 restored, including two of the ceramic based DeForest tubes, very happy about that.

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