[R-390] R-390 Digest, Vol 261, Issue 6
Bart Youngblood
bart.youngblood at gmail.com
Sun Apr 19 13:27:41 EDT 2026
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:
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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
> >>>
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> >>
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> >>
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> >
> >
> >
> > ------------------------------
> >
> > 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
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
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> > 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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