Hi All,
I have done a lot of 1950's Zeniths, so I thought this would equip me well to do the king of 1950's Zeniths.
It looks like I was wrong. Bad tubes that cost $30 was something I never thought could exist other than an eye tube.
However, no silver Mica disease. That is nice, but I know how to handle that.

Enough moaning. My question is this. I thought the 50A1 wasn't supposed to glow. This one does, and it does not glow evenly, having red sections in its filament and dark sections. Is this tube weak?

Best Regards,

Bill Grimm

Bill, I've never seen a 50A1 that worked, so I can't answer your question. For the TransOceanics I've fixed up, I replaced the dud 50A1s with a power resistor.

But, if the voltages are correct, then the 50A1 must be doing its job.
Doug

:Hi All,
: I have done a lot of 1950's Zeniths, so I thought this would equip me well to do the king of 1950's Zeniths.
: It looks like I was wrong. Bad tubes that cost $30 was something I never thought could exist other than an eye tube.
: However, no silver Mica disease. That is nice, but I know how to handle that.
:
: Enough moaning. My question is this. I thought the 50A1 wasn't supposed to glow. This one does, and it does not glow evenly, having red sections in its filament and dark sections. Is this tube weak?
:
:Best Regards,
:
:Bill Grimm

By the way, what is that $30 tube you mention? If it's a 1L6 converter, you can substitute a 1R5. Supposedly, a 1R5 might not work well on the high-frequency bands, but I've had no problem.
Doug

:Bill, I've never seen a 50A1 that worked, so I can't answer your question. For the TransOceanics I've fixed up, I replaced the dud 50A1s with a power resistor.
:
:But, if the voltages are correct, then the 50A1 must be doing its job.
:Doug
:
::Hi All,
:: I have done a lot of 1950's Zeniths, so I thought this would equip me well to do the king of 1950's Zeniths.
:: It looks like I was wrong. Bad tubes that cost $30 was something I never thought could exist other than an eye tube.
:: However, no silver Mica disease. That is nice, but I know how to handle that.
::
:: Enough moaning. My question is this. I thought the 50A1 wasn't supposed to glow. This one does, and it does not glow evenly, having red sections in its filament and dark sections. Is this tube weak?
::
::Best Regards,
::
::Bill Grimm

Hi Doug,
Thank you for responding to my qustion. All the voltages look OK, so the 50A1 must be OK. Just curious, what resistor would work there?

The $30 tube is a 1L6. It tests weak at best. I put a 1R5 in the radio and sensitivity improves, giving me a second opinion that the 1L6 is bad. However, the local oscillator on the 1R5 seems to quit above 4MHz. Is that to be expected?

By the way, all the cheap tubes are fine. There I am moaning again. I promise to stop.

Best Regards,

Bill Grimm

Bill: I seem to recall a 1.2K-ohm resistor being a 50A1 replacement. You'd have to guestimate the power disipation from the schematic voltages - and double for safety. After substituting the dropping resistor, you should check the voltages.

The 50A1 tube isn't visible, even with the TransOceanic's back off. And, anyway, it's totally unnecessary in the civilized world where AC line voltages are reasonably in spec. So, you could sell your good 50A1 and use the proceeds to pay for your 1L6?

Your observation about the 1R5 pooping out at higher frequencies matches the reports of others. Maybe I was just lucky that my 1R5 works across all the bands?
Doug

:Hi Doug,
: Thank you for responding to my qustion. All the voltages look OK, so the 50A1 must be OK. Just curious, what resistor would work there?
:
: The $30 tube is a 1L6. It tests weak at best. I put a 1R5 in the radio and sensitivity improves, giving me a second opinion that the 1L6 is bad. However, the local oscillator on the 1R5 seems to quit above 4MHz. Is that to be expected?
:
: By the way, all the cheap tubes are fine. There I am moaning again. I promise to stop.
:
:Best Regards,
:
:Bill Grimm

Bill- Go to the Search heading at the top of this page and type in 50A1 to search the entire site. You'll find resistor info,etc to sub the ballast if you need to. Sounds like it may be getting gassy? -Walt.

Hi Walt,
Thank you for the advice. I had forgotten about that search capability. A 1.3K 10 watt seems to be the proper replacement size. An optional 9 volt zener seems to be a good idea, too.

Best Regards,

Bill