[Phlogiston]

First, I put this here since I can't think of a Philco that uses an 01A.

I just looked up 201/01A postings on E-Pay. It looks like prices are up since the low around 4 years ago. Then it was not uncommon to be able to buy these for $10 - $15. Looks like it is $20 - $25 now. One thing you can be sure of - they aren't making new ones.

There is plenty of history on the 201 online so some research should be done, if you are interested.

I have more than enough UX201s to last a long time, especially considering that the plastic base, long pin tube was really only original equipment for about a year with the previous versions running back to about 1920. And since I try to put the original brand/type of tube in my restorations - well, that is why I have plenty.

But, most people only care about the radio working - and being cheap (me too).

I have thought about this for a while and it is a sure thing that I am not the first. Here is how it goes - build a replacement for the UX201/01A for less than $2.50.

You are gonna' need a 4 pin base like off of an 80. Depending on your radio, this base may or may not need to have the side pin for the Bayonet/UV base - depends on how old your radio is. Then a standard 7-pin miniature socket. These should both be available from your junk drawer.

Then look in your tube stash for a 6C4. I picked this tube for it's characteristics - basically it is 1/2 of a 12AU7 and it is called a power triode by RCA. If you don't have one, E-Pay has some for about $1 some NOS. I just bought 15 about half of them NOS for an average of $1.10 - Sorry, there will be more.

Then 4 wires and a jumper will connect the 2 sockets/plugs. Connect the 7 pin socket, pins 3 and 4 to the big pins, pin 6 goes to the small pin on the right (Pins up, big pins closest to you) and the plate to the remaining small pin. Then place a jumper between pin 3 (fil) and pin 7 on the 7 pin socket. This is the cathode connection.

To test as a 201 use the same settings as an 01A but you will need to lower the bias from about 48 to near 0.

In testing this tube works great as an audio amp including a 171 or 112 . I tested it in my AK 20 in all positions with setting as they were for the 201s and it worked great as a detector and audio amp improving tone and level some and about the same as the 201 in the RF amp sockets.

BUT, BUTTTT it is a 6V tube. Yeah, it doesn't matter. It takes about 10 seconds to warm up. BUT, BUT, BUT the cathode will be damaged - well if it goes to "sleep", just run it at 6V in your tube tester for a while. In reality these tubes were often run at low filament voltages to keep noise down in audio circuits and as a way to get bias for finals - look up some of the Fisher amps using the 12AU7 and 12AX7. It will be fine.

Also it only draws .15A of filament current. This will make your power supply/battery happy.

   

I potted this one in tar, but I think I'll use resin on the next one.

Not sure how a radio with 5 of these will work.

I'm going to post this on my blog soon, so get your 6C4s before the run.

[Arran]

Russ;
  I seem to recall that 6C4s were used in TV sets, so that may explain why they are cheap and easy to come by. I'm not sure what the specs are however, I will have to look them up in one of my tube manuals. You are right about the heater voltage not really being an issue, though I'm not sure how an indirectly heated tube will respond to being operated through a rheostat. Along these same lines I wonder if you could use another common, though slightly more expensive tube such as a 6K6G/GT, with the plate and grids tied together, those are 300 ma tubes as opposed to 250 ma for a 01A, though they might not work dues to the B+ in a 20s battery set being capped at 135 vdc.
Regards
Arran

[Radioroslyn]

https://www.flickr.com/photos/42774321@N...otostream/
Instead of using a 6c4 a 6J6 maybe a good choice as they are plentiful and cheap.

[Phlogiston]

Guys, the 6C4 is really cheap, around $1.

As I said it is 1/2 of a 12AU7.

One of my objectives was to equal or reduce filament consumption since most of these radios are being run on power supplies. The 6J6 draws .45A. Five of these are gong to be rough on the rheostats.

I have run this conversion through every position and setting on the small box AK20 and it works very well. The only thing I have not tried is running 5 of them in the same radio. It may be a while before I make 5 of them.

I just completed adaptors for the UV and UX-199 as well as the UX-120. These use a different tube(s). To me, this adaptor is much more useful. Most UX tubes are not that hard to get but the UV tubes are becoming expensive - and I would not want to blow one up while testing a restoration.

I do not intend to make any of these to sell but I thought some of you might need some for the same reasons that I do.

[Ron Ramirez]

I like the idea. Thanks for sharing, Russ.

Years ago I found that a 1G4GT worked great as an 01A substitute, with a suitable adapter. Only thing is, they require far lower filament voltage (2 volts), so you have to make a complete set of adapters for a five tube radio.

I have a few three dial sets including an AK 20 Big Box, Super-Zenith VIII and a Slagle, so I would like to try the 6C4 tubes (with adapters) sometime for myself.

[Phlogiston]

Yeah, Ron, give it a try.

I'll get to the post on the 199 tubes ASAP - just took pictures. As I said, I find this more useful and will use them in testing the old dry-cell radios.

[Arran]

That reminds me, someone gave me a box of some old copies of the Antique Radio Classified. In several of these old magazines there were ads for some sort of solid state substitute for 01As, 99s, etc., that fitted across the pins of the original tubes. I would guess that they used some sort of field effect transistor, and some peripheral components on the wafer on which the substitute was constructed. Of course if the tube is missing altogether these would not be all that useful.
 The 6C4 obviously works, and gets the job done, you may also be able to run the filaments on 6.3 volts AC and skip the battery eliminator,  I'm just not that crazy about the appearance, although at least it's still a vaccuum tube and not "sand". I may even have some in my TV tube stash already, that or 6AQ6s, a 6AV6/6AT6 would be another option, if you disregard the diodes. I read an article about battery tubes substitutes in the Old Timer's Bulletin, but this was with regard to replacing WD11s or WD12s, the 1G4 was one that was suggested, but they preferred to use a triode connected 1C5 or 1Q5, all are 1.4 volt battery types by the way, easy for a Radiola 3 or 3A, but more work for an A.K or a Freshman Masterpiece.
Regards
Arran

[Phlogiston]

If it is possible to run the 6C4 on AC filament voltage it would require all 5 tubes to be replaced. This would probably still result in some hum since the cathode is jumpered to the filament.

I agree on the looks. I would not display a radio with these in it. My intentions were to use them for testing. The fellow that made similar substitutes a few years ago had some test tube glass to cover them with - even silvering some of them to replicate the getter. Maybe somebody could find some at a lab glass vendor. I haven't looked.

The problem with the WD-11 is the base, not just the pins. The pin spacing on a WD-11 is different than the 199, 80, 45 and so on. So you would have to make the whole base for an adaptor.

[Arran]

Russ;
  That was the other part of the article, was how to make a WD-11 base, it has four pins, but I seem to recall that it had three pins that were the same size, and the spacing was different as well. The WD-11 sub is pretty much a given if you want to actually operate an old radio, they are fragile, and were poor design, even from new, such that they discontinued manufacturing radios with them within a few years of their introduction. I don't know when they discontinued making replacement WD-11s and 12s but it was probably within five years of them coming out, such that even RCA started offering adapters so that people could substitute them with 199s instead. There are way more sets that use WD-11s and 12s then there are replacement tubes, so it's a good thing that Westinghouse chose 1.1 Volts as a filament voltage for those sets as 1.4 volts was the standard for the very much more common octal/loctal based tubes from the 1940s, though the current draw is lower 100 ma verses 250 ma. I can't recall whether they mentioned anything about adding a resistor in parallel with the filament to bring up the current draw, although it shouldn't be needed if the rheostat has enough range.
Regards
Arran

[Phlogiston]

OK, I have posted pictures and videos of the substitute tubes in action.

My one conclusion that is not in the blog is that the sub may actually be more suited to a low performing tube rather than the NOS ones I was using - closer to 600 Gm.

Don't forget to like the blog post. These posts take days to prepare.

https://www.russoldradios.com/blog

[Arran]

Russ;
  The 199 substitute looks good, it doesn't even look out of place when compared to the early 199s with the evacuation tip on top. I will have to keep this in mind if I run into an early RCA dry cell set. I also see what you mean about the difference in pinout between the UV-199 and the UX-199; the UX has a standard pinout similar to a 01A, #26, or a #30, the UV-199 has the grid connected to pin 1, the filament connected to pin 2, and the plate connected to pin 3. If you wired the bayonet base to fit the pin-out of a UX-199 the 3V4 or 3S4 will become a flashbulb. Of the two tubes the 3S4  looks like it may be a better match as a substitute in terms of filament current, not that it matters on a battery eliminator, though the gain will still be higher then a 199.
Regards
Arran

[Phlogiston]

Besides availability, mostly in my inventory, the reason that the 6C4 was chosen over the 6S4 was the rated screen voltage. Since the easiest application was to strap the plate to the screen, each at 90 volts, this was easier than getting 67V for the screen in the 6S4.

[Arran]

Russ; 
  I guess you were speaking about the 3S4 verses the 3V4 rather then a 6C4 verses a 6S4 when you were speaking about plate and screen voltage limits. Now that you mention it the 3S4 seems to have been the output tube of choice in various "personal" type radios of the 1940s, the very kind that would employ a 67-1/2 "B" battery, such as a G.E model 140, it would probably be fine as a detector or RF amp, depending on the set. It seems that the 6S4 was used a vertical deflection amp in some TV sets, filament current 600 ma, so nobody bother with that one as a 01A substitute.
Regards
Arran

[Phlogiston]

Yes, that is why I was considering using the 3S4 as a replacement for the UX120 output tube. But, the 3S4 really isn't any different spec.-wise than the 3V4 except for the 67V screen. I don't think that there would be a noticeable improvement in audio output. In the actual application of the sub. 3V4 there is plenty of output to cover a UV120. At this point my interest would be in adding a resistor between the plate and screen for the 3S4 and evaluating it as an additional option.

[Arran]

Russ;
  What about trying a 3Q4 in place of the 3S4, they appear to have the same pinout, and the B+ rating is higher on the 3Q4? That way you can use the same adapter, however I think that the 3Q4 is basically the same tube as a 3V4 electrically.
Regards
Arran