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Old 11-27-2015, 05:38 PM
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Tubejunke Tubejunke is offline
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Zenith transoceanic and other portables with 1l6 emissions mystery

As of late I have aquired several Zenith radios using the infamous and expensive 1L6 "converter" tube. I started with a single Transoceanic and through trial and error I destroyed a set of the very delicate 1.4VDC tubes. I use my SelectAvolt supply now to power all of these sets until I feel that they are ready for full wall current.

I want to say that Zenith did a wonderful job of making some of the most sensitive radios that I have ever seen during this "wave magnet" period of the 40s and 50s. I really love them. I can find something to listen to at any time of the day and of course night time DXing is a blast. But the reason I made this thread is that I don't understand the nature of the 1L6 vacuum tube.

As of right now I have 3 radios playing just fine. None of the 1L6s show good on two known good (very good) tube testers. One is almost out of the red (bad) area and works fine. Another is about 1/4 of the way up the red (bad) on the scale and works just as fine. The only one that doesn't work is one that shows absolutely no emissions. As good as the radios work with them, I can't help but wonder what one actually showing good would do in a radio. Perhaps better reception on the shortwave bands?

Also, has anyone ever tried one of the solid state replacements now made due to the long dwindling supply of 1L6s. I think if it works that it would be a worthy investment for anyone keeping one of these radios alive.

By the way, my other Zeniths similar are the 5G41 "Flip Top" units. Really neat little radios but only receive broadcast. I best get any good 1L6 out of those and put in the 1R5 (I think) suitable replacement that people are using in Transoceanic models. Supposedly they will allow broadcast (AM) reception, but fail to pull in shortwave which to me is no good if you have a Transoceanic radio. I mean why make one of those beauties into a simple AM radio?
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Old 11-27-2015, 09:33 PM
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IIRC, there's a loctal version of the 1L6. 1LA6 that would electrically substitute, except for an extra 1 pF capacitance. It's a lot bigger, though. I think Bill Turner, back in the days of rec.antiques.radio+phono, used to sell adapters to do this.
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Old 11-28-2015, 12:05 AM
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I dislike the idea of troubleshooting/repairing/restoring a set with a 1L6 installed during the process....It is a MUCH better idea to put a 1R5 in the set until you have all critical parts replaced and it is working correctly on AM. It is much better to blow a 1R5 than a 1L6 while fixing it.
Other than as a restoration safety (or a poor mans substitute until a 1L6 can be gotten) I see no use for the 1R5 in shortwave sets.
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Old 11-28-2015, 12:24 AM
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Good info! Especially as I thought that the 1LA6 was a direct substitute via a 7 pin min. to loctal adapter. Didn't hear of a capacitance change. My point hidden in my long winded post was to find out why 1L6s of low to almost no emissions work great in 2 different radios and tested on two different testers.

I don't have any 1L6 that actually tests good, but have two radios that work really well. Very sensitive radios that pick up stations that I don't even think about on the average radio. Again, the only 1L6 that I have that doesn't work has no readable emissions. I haven't seen any footnotes in test setup sheets indicating good under a lowered range such as I do on certain old loctal tubes like the 1LN5 which states good over 30 which is very low on the scale
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Old 11-28-2015, 12:40 AM
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Sorry everybody. This thread was supposed to be under antique radio. Can admin. please move this? Title mistake as well ("1l6"). It pays to proof read!
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Old 11-28-2015, 01:14 AM
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Quote:
Originally Posted by Tubejunke View Post
Good info! Especially as I thought that the 1LA6 was a direct substitute via a 7 pin min. to loctal adapter. Didn't hear of a capacitance change. My point hidden in my long winded post was to find out why 1L6s of low to almost no emissions work great in 2 different radios and tested on two different testers.

I don't have any 1L6 that actually tests good, but have two radios that work really well. Very sensitive radios that pick up stations that I don't even think about on the average radio. Again, the only 1L6 that I have that doesn't work has no readable emissions. I haven't seen any footnotes in test setup sheets indicating good under a lowered range such as I do on certain old loctal tubes like the 1LN5 which states good over 30 which is very low on the scale
Some circuits simply don't care as much as your tube tester does how good a tube is. I've had a number of radios that would work decently on weak tubes.
A converter tube is acting more as an oscilator/mixer stage than a gain stage (mixer tubes generally are not a high gain stage relatively speaking IIRC). The big gain occurs in the IF and to a lesser extent the RF on sets with a RF stage. The AVC likely compensates for the low gain of a weak tube by cranking up the amplification factor of the other tubes it controls.... Where you may notice a performance difference, if you get a good 1L6, is on stations (on a band NOT swamped with RF noise) that with the volume maxed are BARELY loud enough to hear (in this case the AVC is running all tubes at max gain so sensitivity is based primarily on tube health). Those stations will come in louder with a better tube or become unreceivable with a swap to a weaker one.
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