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

[Alex Hopper]

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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