[Milsurplus] looking for R-390 and -A meters

Fri Feb 15 15:47:11 EST 2019

I still have a fair number of the Weston 1011  1-3/4” square 0-1mA meters as described by Pete.  Price is still $15 plus shipping.   As Pete mentioned, the scale on these will need re-doing if you want actual numbers on it.

I have also sold these for use in other sets such as T-195 and R-392 but have had no feedback from anyone on how they adapted it electrically.

Robert Downs

From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Jim Whartenby
Sent: Friday, February 15, 2019 13:51
To: milsurplus listserv
Subject: Re: [Milsurplus] looking for R-390 and -A meters

Brian

A VU meter is a VU meter so if it fits, it is good to go.

The Carrier Level meter is a different story.  I have used meters from other military radios as replacements  The meters used are the same physical size and appearance of the original Collins meters so if you didn't know beforehand, I doubt that you would notice any difference.  

Here is a note from 2006 by Pete Williams from "the land down under" on the procedure to go from the original 10 ohm meter movement to one that uses a 100 ohm / 1 mA meter movement.

"Hi... While 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 the 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 160 ohm 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 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 for test.

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 have used the above procedure with great success on several R-390As.  The meters I used were from several SRR-13 receivers that had I scrapped due to physical, smoke and fire damage.  Most of these receivers were missing modules and would have required much more effort to bring back to life then I was willing to expend.  The more complete receivers I have repaired or have saved for a rainy day.  The SRR/FRR series of receivers are good performers and don't deserve the reputation they seem to have, IMHO.  Plus the fact that they used mechanical filters, long before the non-A R-390 receiver entered inventory.

If you cannot find appropriate meters, let me know and I'll check my box of SRR/FRR spare parts for meter sets.

Regards,

Jim

I wonder why people argue over the 10% of their differences and ignore the 90% they agree on?

On Friday, February 15, 2019, 8:35:45 AM CST, Brian Harrison <briankn4r at gmail.com> wrote: 

Hi all,

I’ve come into a few R-390s and -As with no meters

Would anyone on the list have any for sale?  Or know of a quantity source?

Tnx and please email me off list

briankn4r at gmail.com

(also I’m good on QRZ)

Tnx and all the best,

brian

kn4r

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