[R-390] 26Z5W Tubes - Other Devices?

Fri Apr 17 16:49:56 EDT 2026

What I've done is solder teflon insulated Kynar wire jumpers at the base of 
the series filament pins of a 12BH/Y7A tube to the corresponding pins. IIRC 
from pin 4 to pin 2 and from pin 5 to pin 7 right at the base of the 
tube.(Check to be sure)

I file a slight groove are the base of the pins and then solder using silver 
bearing solder...

I've never had one fail, and likely never will...

73...Jordan...

----- Original Message ----- 
From: "Jim Whartenby via R-390" <r-390 at mailman.qth.net>
Cc: "R-390 Mailing List" <r-390 at mailman.qth.net>
Sent: Friday, April 17, 2026 2:04 PM
Subject: Re: [R-390] 26Z5W Tubes - Other Devices?

> Alex
>
> Why not just replace the 6BA6 (aka 5749) tubes with 12BA6 tubes and 
> eliminate the ballast tube replacement heat entirely?
>
> Jim
> Logic: Method used to arrive at the wrong conclusion, with confidence. 
> Murphy
>
>    On Friday, April 17, 2026 at 12:49:43 PM CDT, Alex Hopper 
> <ahopper0216 at gmail.com> wrote:
>
> Thanks for your responses! Makes me wonder what came first: the R-390 or 
> the 26Z5W
> Also - while we’re on the topic of the power supply, what is the best 
> method for replacting the 3TF7? I know this is a broad topic, but I’d 
> eventually like to replace this tube in the 390 I am currently working on, 
> and I’d like to do it the simplest way possible without any major 
> modifications. I believe you can use a high wattage resistor?
> -Alex
> Jordan Arndt via R-390 <r-390 at mailman.qth.net> schrieb am Fr. 17. Apr. 
> 2026 um 13:44:
>
> Jim and the group...you can find the info in the Power Supply diagram on
> page 5-50 of the Y2K manual....
>
> I also added ceramic caps shunting the 1N5408 diodes to kill any rectifier
> "hash". don't recall offhand the value, but they're either .1 or .01uF 1kV
> ceramics.
>
> 73...Jordan VE6ZT
>
>
> ----- Original Message ----- 
> From: "Jim Whartenby via R-390" <r-390 at mailman.qth.net>
> To: "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Friday, April 17, 2026 10:57 AM
> Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
>
>
>> JordanWhich manual are you referring to?JimLogic: Method used to arrive 
>> at
>> the wrong conclusion, with confidence. Murphy
>>
>> On Friday, April 17, 2026 at 11:00:00 AM CDT, Jordan Arndt via R-390
>> <r-390 at mailman.qth.net> wrote:
>>
>> While I do have a couple of spares, I found that a 1N5408 will simply 
>> plug
>> in to the tube socket very very tightly, so I added the dropping resistor
>> in
>> the Audio deck as per the manual...I have one 390A with the diodes and 2
>> with the required tubes...
>>
>> 73...Jordan VE6ZT
>>
>> ----- Original Message ----- 
>> From: "Alex Hopper via R-390" <r-390 at mailman.qth.net>
>> To: "R-390 Mailing List" <r-390 at mailman.qth.net>
>> Sent: Friday, April 17, 2026 9:16 AM
>> Subject: [R-390] 26Z5W Tubes - Other Devices?
>>
>>
>>> Hi All,
>>>
>>> I am going through an R-390/URR at the moment, and recently experienced 
>>> a
>>> shorted (filament to cathode) 26Z5W rectifier tube in the power supply.
>>> Thankfully I had a spare on hand, and was able to find a few more online
>>> to
>>> keep in my 'stock'.
>>>
>>> But this led me to wonder - were there any other devices that used the
>>> 26Z5W? I know they are a fairly rare/uncommon tube these days (hence the
>>> outrageous prices for them), but I have never seen another piece of
>>> equipment use the 26Z5W.
>>>
>>> Just curious.
>>>
>>> -Alex
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