[R-390] 390A Line Level meter replacement..?

Fri Nov 5 22:53:56 EDT 2021

Meter board discussion thread here:

https://mailman.qth.net/pipermail/r-390/2018-June/057208.html

On Fri, Nov 5, 2021 at 10:52 PM Bob Weiss <bobweiss1967 at gmail.com> wrote:

> I still have a few of the opamp PCBs I manufactured for converting
> ordinary panel meters for use in the R-390 carrier circuit. Info in thread
> here:
>
> https://live.staticflickr.com/1722/41820958175_fe8d826471.jpg
>
> Picture here:
> https://live.staticflickr.com/1722/41820958175_fe8d826471.jpg
>
> 73,
> Bob Weiss N2IXK
>
> On Wed, Nov 3, 2021 at 1:49 PM Jim Whartenby via R-390 <
> r-390 at mailman.qth.net> wrote:
>
>> David and the group
>> I have successfully used Pete Williams' meter modification published on
>> the Milsurplus list back in June of 2006.  I see that you and Dave assisted
>> Pete in fleshing out this modification.  For everyone else, here it is in
>> Pete's own words:
>>
>> "HiWhile some of you guys have been getting legless from taking the plate
>> caps off 807's, some of us at the other end of the  day have been active in
>> being practical in adapting surplus meters for the carrier level function
>> in R-390A.
>>
>> The original meter has an internal R of around 10 Ohms and
>> the replacement meter I have (ex W5cab) has an Internal R of around
>> 103 ohms.  It has a  FSD of 1 mA.  The scale plate changed per foto details
>> available on the net.
>>
>> Altho' it deflects, the reading is a fraction of the original.  Following
>> suggestions made by David Wise and Gary Gitzen,modifications made to the
>> meter bridge circuit gave identical results to that generated with original
>> meters.
>>
>> Not only was meter deflection approximately the same (Even readings from
>> original meters varied under same test  conditions) but the parameters of
>> linearity and AGC also remained identical to readings obtained with the
>> original meters during the tests.  Time constant values also appeared to be
>> the same as original.
>>
>> MODIFICATION.  Refer to Fig 22 on page 36 of manual TM 11-5820-358-35.
>> Replace R524 with a 600 ohm resistor.
>> Replace R548  with a 160ohm resistor.  Both are easy to get at.
>> Remove R537 a 22 ohm resistor from the  carrier meter adjust pot.
>> Remove the shorting link from the center wiper terminal of this pot and
>> connect the white - blue - orange wire to the  "hot end" of the pot.
>> The  white - blue - green wire stays on the center wiper and it
>> is already connected to the + side of meter M102.  The  white  wire stays
>> going to chassis.
>> Zero the meter as per the manual and that's it.
>>
>> NOTE:  Other meters of greatly differing IR's may require modification of
>> the resistor values.  None were available fortest.
>> Thanks to Dave and Gary for interest and assistance with these
>> modifications.
>> Purists can get on with evacuating 807's!
>>
>> Cheers
>> Pete D . Williams
>> METUNG 3904
>> Australia
>> jupete at bigpond.net.au"
>>
>> I always enjoyed Pete's posts, as you can see, he was a character!   He
>> and Nolan Lee made quite a few posts that were both informative and a joy
>> to read.  I miss them both.
>>
>> The meters I have used in the above modification came from perhaps a half
>> dozen SRR-13's and FRR-23's that I got at a local estate auction many years
>> ago.  I believe that all of the radios at this auction came from the estate
>> of Dr James Black but W5OR certainly has a better memory of this then I
>> do.  Most of these radios were damaged in a fire, some scorched, some with
>> smoke and fire extinguisher residue.  The VU meter was a drop-in
>> replacement, the Carrier Level meter responded well to the above mod.
>>
>> Let's hope that I have properly formatted the above so that it is
>> readable.  I think that this list does not like my browser!
>>
>> Regards,
>> Jim
>> Too much agreement kills a chat.  E. Cleaver
>>
>> -----Original Message-----
>> From: David Wise <David_Wise at Phoenix.com>
>> To: Jacques Fortin <jacques.f at videotron.ca>; 'Jordan Arndt' <
>> Outposter30 at shaw.ca>; 'R-390 Forum' <r-390 at mailman.qth.net>
>> Sent: Wed, Nov 3, 2021 10:53 am
>> Subject: Re: [R-390] 390A Line Level meter replacement..?
>>
>> Gary Gitzen and I developed a fairly simple IF deck mod that allows use
>> of virtually any 1mA or smaller meter movement for the Carrier function.
>> No op-amp required.  The mod also improves the action of the Carrier Zero
>> adjuster.  I believe it's in the Pearls of Wisdom archive.
>>
>> Dave Wise
>> SWL (inactive)
>>
>> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
>> On Behalf Of Jacques Fortin
>> Sent: Wednesday, November 03, 2021 7:46 AM
>> To: 'Jordan Arndt'; 'R-390 Forum'
>> Subject: Re: [R-390] 390A Line Level meter replacement..?
>>
>> Hello Jordan,
>>
>> Wow ! Good find !
>> If only there are also some matching style 1mA fs, 18 ohms meters with a
>> 0-100 dB dial for the RF Level, now...
>> But OK, I am asking too much...
>> Let us know how they work when you will have those in hand !
>>
>> 73, Jacques, VE2JFE
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