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

[Jim Whartenby]

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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