[R-390] R-390 Digest, Vol 261, Issue 6
David Wise
d44617665 at hotmail.com
Sun Apr 19 16:08:12 EDT 2026
The 3DW7 runs cool.
________________________________
From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Jim Whartenby via R-390 <r-390 at mailman.qth.net>
Sent: Sunday, April 19, 2026 11:06 AM
To: r-390 at mailman.qth.net <r-390 at mailman.qth.net>
Subject: Re: [R-390] R-390 Digest, Vol 261, Issue 6
Bart
If you believe as I do that heat is the enemy of reliability then anything that one can do to reduce heat will increase reliability. Of all the methods mentioned so far for replacing the 3FT7 or any other equivalent current regulator, the only one that does not add heat to the R-390 is to change the oscillator tubes to their 12 volt equivalents and then connect the tube socket pins together that feed the 3FT7.
Regards,
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy
On Sunday, April 19, 2026 at 12:28:23 PM CDT, Bart Youngblood via R-390 <r-390 at mailman.qth.net> wrote:
I replaced the missing 3TF7 in mine using an LM317. I added a single diode
and capacitor to rectify and filter the AC. Then used the chassis of the IF
deck as a heatsink, with appropriate insulation between the tab of the
device and chassis. Been running it that way for over a year now with no
problems.
Bart
On Sun, Apr 19, 2026 at 12:00 PM <r-390-request at mailman.qth.net> wrote:
> Send R-390 mailing list submissions to
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> Today's Topics:
>
> 1. Re: R-390 Digest, Vol 261, Issue 5 (Russ Dworakowski)
>
>
>
> ---------- Forwarded message ----------
> From: Russ Dworakowski <wb3fau55 at neo.rr.com>
> To: r-390 at mailman.qth.net
> Cc:
> Bcc:
> Date: Sat, 18 Apr 2026 14:00:52 -0400
> Subject: Re: [R-390] R-390 Digest, Vol 261, Issue 5
> Replace with one amp thousand thousan thousand volt DIODES no problem
>
> Sent from my iPhone
>
> > On Apr 18, 2026, at 12:02 PM, r-390-request at mailman.qth.net wrote:
> >
> > Send R-390 mailing list submissions to
> > r-390 at mailman.qth.net
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> > http://mailman.qth.net/mailman/listinfo/r-390
> > or, via email, send a message with subject or body 'help' to
> > r-390-request at mailman.qth.net
> >
> > You can reach the person managing the list at
> > r-390-owner at mailman.qth.net
> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of R-390 digest..."
> >
> >
> > Today's Topics:
> >
> > 1. Re: 26Z5W Tubes - Other Devices? (Jim Whartenby)
> > 2. Re: 26Z5W Tubes - Other Devices? (Jordan Arndt)
> > 3. Re: 26Z5W Tubes - Other Devices? (Alex Hopper)
> > 4. Re: 26Z5W Tubes - Other Devices? (Jim Whartenby)
> > 5. Re: 26Z5W Tubes - Other Devices? (Jim Whartenby)
> > 6. Re: 26Z5W Tubes - Other Devices? (Jordan Arndt)
> > 7. Re: 26Z5W Tubes - Other Devices? (Jordan Arndt)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Fri, 17 Apr 2026 16:57:57 +0000 (UTC)
> > From: Jim Whartenby <old_radio at aol.com>
> > To: R-390 Mailing List <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <1930137684.358139.1776445077388 at mail.yahoo.com>
> > Content-Type: text/plain; charset=UTF-8
> >
> > 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
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Fri, 17 Apr 2026 11:34:19 -0600
> > From: "Jordan Arndt" <Outposter30 at shaw.ca>
> > To: "Jim Whartenby" <old_radio at aol.com>, "R-390 Mailing List"
> > <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <D695BB41C182450A86CBCC3EF529BB1D at Jordan1>
> > Content-Type: text/plain; format=flowed; charset="utf-8";
> > reply-type=original
> >
> > 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
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> >
> > ------------------------------
> >
> > Message: 3
> > Date: Fri, 17 Apr 2026 13:49:29 -0400
> > From: Alex Hopper <ahopper0216 at gmail.com>
> > To: Jordan Arndt <Outposter30 at shaw.ca>
> > Cc: R-390 Mailing List <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID:
> > <CAKPybGaXwt_hPf35gniVAWs8AENVrPy9YxYMfyS+0A7A_QQuDA at mail.gmail.com>
> > Content-Type: text/plain; charset="UTF-8"
> >
> > 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
> >>>> ______________________________________________________________
> >>>> R-390 mailing list
> >>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>>> Help: http://mailman.qth.net/mmfaq.htm
> >>>> Post: mailto:R-390 at mailman.qth.net
> >>>>
> >>>> This list hosted by: http://www.qsl.net
> >>>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >
> >
> > ------------------------------
> >
> > Message: 4
> > Date: Fri, 17 Apr 2026 20:04:14 +0000 (UTC)
> > From: Jim Whartenby <old_radio at aol.com>
> > Cc: R-390 Mailing List <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <1648880017.446350.1776456254219 at mail.yahoo.com>
> > Content-Type: text/plain; charset=UTF-8
> >
> > 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
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> > ______________________________________________________________
> > R-390 mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/r-390
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:R-390 at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> >
> > ------------------------------
> >
> > Message: 5
> > Date: Fri, 17 Apr 2026 19:51:07 +0000 (UTC)
> > From: Jim Whartenby <old_radio at aol.com>
> > To: R-390 Mailing List <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <635739612.406012.1776455467306 at mail.yahoo.com>
> > Content-Type: text/plain; charset=UTF-8
> >
> > Jordan
> >
> > Thanks for the quick reply.
> >
> > I checked page 5-50 of the Y2K manual and found no mention of adding
> voltage dropping resistors when replacing the 26Z5 rectifiers with solid
> state rectifiers.? I then checked "NAVSHIPS-0967-063-2110-FC6-1966 R-390A
> Internal Heat Reduction" and it too has no mention of adding voltage
> dropping resistors.? AFAIK, there is no military sanctioned modification
> that adds these resistors to any military receiver.
> >
> > If the purpose of FC6 is to reduce the heat in the R-390/URR by
> eliminating the heat generated by the 26Z5 rectifiers, then just over 10
> watts of heater power is saved by eliminating the tube rectifiers.? Not
> mentioned is the worst case heat caused by the 26Z5 "internal resistance"
> of 2.2 watts per tube plate when the B+ current is 100 mA per rectifier
> plate.? So for the R-390, as a whole, it is just about 19 watts of heat
> that is eliminated by using solid state rectifiers.
> >
> > Eliminating the voltage regulator would save three times the above in
> waste heat.? In fact, the voltage regulator and the rectifiers account for
> some 40% of the power used by the R-390/URR, not including the oscillator
> heaters.? Since the B+ transformer winding specification for both the
> R-390/URR and the R-390A/URR are the same and both receivers have the same
> B+ current requirements, then eliminating the voltage regulator and using
> the power supply designed for the R-390A/URR will greatly reduce the
> operating temperature of the R-390/URR.
> >
> > Regards,
> > Jim
> >
> > fLogic: Method used to arrive at the wrong conclusion, with confidence.?
> Murphy
> >
> > On Friday, April 17, 2026 at 12:34:20 PM CDT, Jordan Arndt <
> outposter30 at shaw.ca> wrote:
> >
> > 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
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> >
> > ------------------------------
> >
> > Message: 6
> > Date: Fri, 17 Apr 2026 14:49:56 -0600
> > From: "Jordan Arndt" <Outposter30 at shaw.ca>
> > To: "Jim Whartenby" <old_radio at aol.com>
> > Cc: R-390 Mailing List <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <AD9B28F2FA9E4300819C8542475139E9 at Jordan1>
> > Content-Type: text/plain; format=flowed; charset="UTF-8";
> > reply-type=original
> >
> > 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
> >>>> ______________________________________________________________
> >>>> R-390 mailing list
> >>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>>> Help: http://mailman.qth.net/mmfaq.htm
> >>>> Post: mailto:R-390 at mailman.qth.net
> >>>>
> >>>> This list hosted by: http://www.qsl.net
> >>>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> >
> > ------------------------------
> >
> > Message: 7
> > Date: Fri, 17 Apr 2026 14:57:02 -0600
> > From: "Jordan Arndt" <Outposter30 at shaw.ca>
> > To: "Jim Whartenby" <old_radio at aol.com>, "R-390 Mailing List"
> > <r-390 at mailman.qth.net>
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> > Message-ID: <4B407FA3BFB2499FBD7DA971ECD08DF6 at Jordan1>
> > Content-Type: text/plain; format=flowed; charset="UTF-8";
> > reply-type=original
> >
> > Jim...the diagram on that page shows the Diode mod and the subsequent
> > dropping resistor just inside the outline of the audio deck...I believe
> the
> > diode sub was a Navy mod, and they would even pinch the tube socket metal
> > closed to show the mod had been performed...
> > Why...? you got me...!
> >
> > Jordan...
> >
> >
> > ----- 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 1:51 PM
> > Subject: Re: [R-390] 26Z5W Tubes - Other Devices?
> >
> >
> >> Jordan
> >>
> >> Thanks for the quick reply.
> >>
> >> I checked page 5-50 of the Y2K manual and found no mention of adding
> >> voltage dropping resistors when replacing the 26Z5 rectifiers with solid
> >> state rectifiers. I then checked "NAVSHIPS-0967-063-2110-FC6-1966 R-390A
> >> Internal Heat Reduction" and it too has no mention of adding voltage
> >> dropping resistors. AFAIK, there is no military sanctioned modification
> >> that adds these resistors to any military receiver.
> >>
> >> If the purpose of FC6 is to reduce the heat in the R-390/URR by
> >> eliminating the heat generated by the 26Z5 rectifiers, then just over 10
> >> watts of heater power is saved by eliminating the tube rectifiers. Not
> >> mentioned is the worst case heat caused by the 26Z5 "internal
> resistance"
> >> of 2.2 watts per tube plate when the B+ current is 100 mA per rectifier
> >> plate. So for the R-390, as a whole, it is just about 19 watts of heat
> >> that is eliminated by using solid state rectifiers.
> >>
> >> Eliminating the voltage regulator would save three times the above in
> >> waste heat. In fact, the voltage regulator and the rectifiers account
> for
> >> some 40% of the power used by the R-390/URR, not including the
> oscillator
> >> heaters. Since the B+ transformer winding specification for both the
> >> R-390/URR and the R-390A/URR are the same and both receivers have the
> same
> >> B+ current requirements, then eliminating the voltage regulator and
> using
> >> the power supply designed for the R-390A/URR will greatly reduce the
> >> operating temperature of the R-390/URR.
> >>
> >> Regards,
> >> Jim
> >>
> >> fLogic: Method used to arrive at the wrong conclusion, with confidence.
> >> Murphy
> >>
> >> On Friday, April 17, 2026 at 12:34:20 PM CDT, Jordan Arndt
> >> <outposter30 at shaw.ca> wrote:
> >>
> >> 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
> >>>> ______________________________________________________________
> >>>> R-390 mailing list
> >>>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>>> Help: http://mailman.qth.net/mmfaq.htm
> >>>> Post: mailto:R-390 at mailman.qth.net
> >>>>
> >>>> This list hosted by: http://www.qsl.net
> >>>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >>> ______________________________________________________________
> >>> R-390 mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:R-390 at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>
> >>
> >> ______________________________________________________________
> >> R-390 mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/r-390
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:R-390 at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > R-390 mailing list
> > R-390 at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/r-390
> >
> >
> > End of R-390 Digest, Vol 261, Issue 5
> > *************************************
>
>
> _______________________________________________
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> R-390 at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390
>
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