Getting ready clean the band switches and re cap an old G500 that has been waiting for me to get to it. It has a 1L6 in it now. I have a 1LA6. I have searched the forum and can not find any info on subbing the loctal for the 7 pin. I have a loctal socket and a 7 pin header. Is this just a matter of wiring the pins to match?

Jay

Yes, that's all there is to it. Look up both types in a tube manual, and make the corresponding connections. Some radios require minor touch up of the alignment after doing that sub, but most work perfectly on the AM broadcast band since the tubes are electrically equivalent.

http://www.dialcover.com/tubes.html
Scroll down the list to see how BIll made his adapters. Or for $10 you can't go wrong.

The only thing you might have a problem with is clearance if the 1L6 was in a tight spot.

Jay, I also made an adapter to use a 1LA6 in my H500 TO and it works well. IIRC, alignment on 16m was a little difficult though. Just be careful of the difference in pin layout. The 1LA6 has heater connections at pins 1 and 8 with no connection at pin 7.

Neatly done, GSI. I only wish it were possible to ground the shell. I'd wire it to one of the filament pins, then cover the shell with insulating tape to prevent a short.

The OP said he had a G500. That was the first T-O model to use the 1L6. Zenith wasn't sure it would work, and some production had a loktal-size hole punched in the chassis which was filled with a mounting plate bearing the 1L6 socket. On that kind of chassis it should be fairly easy to refit a loktal socket.

Dave Wise

I think the H500 is the same way. If you don't care about the historical accuracy (and, with a G/H500 it's not like it's a collectors item anyway) putting in a regular Loktal socket seems like the best way to go.

Brett

GSI, thanks for the info and data. There is a larger opening for a locktal, but the components under the chassis are so tight, I couldn't even think of messing with it. Just finished the recap and the radio still works. It seemed a lot more difficult working on this tube set than the transistor ones I have done. More parts needed replacing and some 4.7m resistors were almost 8m and the 560 across a filament was 760. I was a little uncertain after reading about recapping and some of the horror stories. I was lucky that the chassis mounted 950 ohm resistors were ok. Took out the selenium. It was putting out 84 volts vs 105. I wired two 1N4007 in series (read that somewhere as a safety factor since who knows where they were made) and took a 75 ohm to get the voltages right for my line voltage.

Hit the band switches with D5 and will let it sit over night and wire up the 1L6 adapter tomorrow. I found that I had a total of 4 1LA6. I have another G500 that is in pieces and no tubes and rough case, so maybe that will be next project.

Jay

Hello,
I have been experimenting just this week with the 1LA6 and adapter on two different chassis. 6A40 and 6L40. Models A600L and L600 respectively.
Here is my shot at making an adapter. The wire you see is coming from the shell just in case I need to use it some time.



I have used a piece of PC board as the base this takes the pressure of insertion quite nicely. With removal though one has to be more carefull and lever the tube up and off. I wonder if any one has experimented with a shield and taking the coonection to the filament? The result is supposed to modify the capacitance?
The 1LA6 seems to be a very willing oscillator and can operate at very low filament voltage. The down side I have found on both the above chassis is significant band shift such that complete alignment was necessary and even with that the the 16m band was impossible to bring in line. A brass slug in the oscillator coil almost makes it but not worth leaving in there as almost is not good enough.
It would be interesting to hear about others failures and sucesses with this mod.

Today I am experimenting with the 50A1 SS circuit. Here are a couple of pics.




I have made it an adjustable supply and am currently moving components around to minimise heat transfer from one component to another, rightway up and also upsidedown operation. So far this regulator looks very tight and operates over a wide range of input voltages. After this I will simulate a short circuit in the chip and see what voltages and currents appear. I am using the Transoceanic B+ and filament supply but instead of the tube filaments I am using an adjustable resistor to simulate various load conditions.
Regards.
David.

Nice looking. My loctal socket is the wafer type and not as nice as yours. Where did you get your parts?
The 1LA6 did mess up alignment. 14mhz ended up where 15mhz was supposed to be. Even with the 1L6 that I have, I could not get that band aligned properly. I don't know why, but I had to take a turn of the osc coil. The slug wouldn't get enough swing. It's all fine now. I like the tone better on this tube set but the 1000s and 3000s seem to have better sensitivity. For the other G500, I will use the 1LA6 and set it up for that tube.


Jay

Hello,
The parts I used have been with me for a number of years.
It seems that subbing for the 1L6 results in compromises. Personaly after studying the miniature tube TO's for some time I think in future I will stay away from them, 2 units are enough. I was going to do a write up of some of my findings vis a vis the filament supply. At this time i believe the original 50A1 and the 1L6 were not good components, ok when brand new but not particularly long lived.
Regards.
David.

I have found the 1L6 or 50A1 to be no better or worse than any average tubes. I have bought TO's with what looks to be rhe original tubes and work fine. They are a little pricey now due to the limited use and hoarding. With the excellent SS replacements now available the hoarding will ease up and you see plenty for sale.

I wonder if a surge limiter would increase the life of the 50A1?

Carl