[MRCA] MRCA Digest, Vol 261, Issue 41

[Paul Nell]

A variac used when powering tube gear, solid state or tube
rectification will eliminate the initial high B+ and minimize thermal
stresses in all tubes.

73's, Paul

On Sat, Jan 24, 2026 at 2:30 PM <mrca-request at mailman.qth.net> wrote:

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> Today's Topics:
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>    1. Re: R390A dropping resistor value (Ray Fantini)
>    2. Re: R390A dropping resistor value (Doran Platt)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 24 Jan 2026 17:42:18 +0000
> From: Ray Fantini <RAFANTINI at salisbury.edu>
> To: Mike Feher <n4fs at eozinc.com>, 'Bill Mellema' <n3wm at yahoo.com>,
>         'Jeep   Platt' <jeepcomms at outlook.com>, 'Military Radio Collectors
>         Association'    <mrca at mailman.qth.net>
> Subject: Re: [MRCA] R390A dropping resistor value
> Message-ID:
>         <
> DM8P220MB0472999CB89FC869B7C7E7F2B895A at DM8P220MB0472.NAMP220.PROD.OUTLOOK.COM
> >
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> Content-Type: text/plain; charset="windows-1252"
>
> I used to do a lot of replacement of rectifier tubes but not so much
> anymore. The advantages of SS Diodes are obvious, no heat load and higher
> B+ but the thing that sticks out most in my mind is that when you turn the
> radio on with solid state diodes the B+ supply goes to stupid levels until
> the rest of the tubes light up and that can cause stress on the components
> in the radio. Also, somehow at first the idea was to replace tubes that may
> not be easy to obtain but have to say I have enough 5Y3 and 6X4 tubes
> around here to last a lifetime and then some. With the R-390 think you have
> a better argument being the two rectifier tubes they are using are not that
> common, and heat load in the R-390 and A version has always been an issue.
> Least thats me, your results may be different.
>
> Ray F/KA3EKH
>
> ________________________________
> From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on
> behalf of Mike Feher <n4fs at eozinc.com>
> Sent: Friday, January 23, 2026 9:46 PM
> To: 'Bill Mellema' <n3wm at yahoo.com>; 'Jeep Platt' <jeepcomms at outlook.com>;
> 'Military Radio Collectors Association' <mrca at mailman.qth.net>
> Subject: Re: [MRCA] R390A dropping resistor value
>
>
> CAUTION: This email originated from outside of Salisbury University.
> Please exercise caution when clicking links or opening attachments from
> external sources.
>
>
> On a similar subject, I always change out the 3TF7 and put in a dale
> chassis mount 50 ohm resistor. Works great. 73 ? Mike
>
>
>
> Mike B. Feher, N4FS
>
> 89 Arnold Blvd.
>
> Howell NJ 07731
>
> 908-902-3831
>
>
>
> From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On
> Behalf Of Bill Mellema via MRCA
> Sent: Friday, January 23, 2026 9:11 PM
> To: Jeep Platt <jeepcomms at outlook.com>; Military Radio Collectors
> Association <mrca at mailman.qth.net>
> Subject: Re: [MRCA] R390A dropping resistor value
>
>
>
> Great?.thanks Jeep
>
>
>
> Bill N3WM
>
>
> Sent from Yahoo Mail for iPhone<https://overview.mail.yahoo.com/?.src=iOS>
>
> On Friday, January 23, 2026, 7:30 PM, Jeep Platt <jeepcomms at outlook.com
> <mailto:jeepcomms at outlook.com>> wrote:
>
> Bill, I have the Navy book that shows solid-state rectifiers.  I will look
> it up in the morning...
>
> Jeep K3HVG
>
>
>
> Sent from my Verizon, Samsung Galaxy smartphone
> Get Outlook for Android<https://aka.ms/AAb9ysg>
>
> ________________________________
>
> From: mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net> <
> mrca-bounces at mailman.qth.net<mailto:mrca-bounces at mailman.qth.net>> on
> behalf of Bill Mellema via MRCA <mrca at mailman.qth.net<mailto:
> mrca at mailman.qth.net>>
> Sent: Thursday, January 22, 2026 8:23:33 PM
> To: Military Radio Collectors Association <mrca at mailman.qth.net<mailto:
> mrca at mailman.qth.net>>
> Subject: [MRCA] R390A dropping resistor value
>
>
>
> Guys,
>
>
>
> I'm in the process of solid stating the power supply on a R390A. I need
> the value of the series resistor listed in the field change.
>
>
>
> If anyone can help, I would appreciate it.
>
>
>
> Best 73's
>
>
>
> Bill N3WM
>
>
>
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> Message: 2
> Date: Sat, 24 Jan 2026 14:29:50 -0500 (EST)
> From: Doran Platt <jeepp at comcast.net>
> To: "mrca at mailman.qth.net" <MRCA at mailman.qth.net>
> Subject: Re: [MRCA] R390A dropping resistor value
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> End of MRCA Digest, Vol 261, Issue 41
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