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Simpson VU meter repair
Simpson VU meter repair
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Old 24th November 2020, 01:28 AM   #1
BossOrgan is offline BossOrgan
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Default Simpson VU meter repair

Hi all,
I am restoring a Raytheon RC10 tube broadcast console from the 1940s. The large (4") Simpson VU meter is not working.
I have taken the meter apart, and inside the meter there are two wirewound resistors. The resistor that attaches to the + input terminal is open. I am trying to find out the correct value for this resistor. Can anyone help me?
Thank you
Tyler
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Old 24th November 2020, 01:59 AM   #2
rayma is offline rayma  United States
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This RC-11 manual has some RC-10 info, but only this much on the meter:
VU Meter: 0-1 ma DC Weston Model 862
https://www.steampoweredradio.com/pd...e%20Manual.pdf

Since most such meter movements have a basic 50uA sensitivity, you should be able to calculate
the value of the bad resistor from the value of the good resistor and the 1mA full scale spec.

Last edited by rayma; 24th November 2020 at 02:11 AM.
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Old 24th November 2020, 02:18 AM   #3
HollowState is offline HollowState  United States
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These meters have an internal rectifier assembly like all "real" VU meters have. I just happen to have one of these near by. So I opened it and measured both resistors. The one on the right measures 1.099K ohms. So it's safe to call it 1.1K at probably 1%. The other resistor at the top goes across the rectifier and measures 718 ohms in one direction and 2.810K in the other. All values include roughly 3 ohms lead resistance. Hope this helps. (Had I used one of my Agilent DMMs I could have nulled that out, but the B&K DMM was more handy)
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File Type: jpg Simpson VU.JPG (127.6 KB, 115 views)
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Last edited by HollowState; 24th November 2020 at 02:24 AM.
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Old 24th November 2020, 02:24 AM   #4
BossOrgan is offline BossOrgan
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Hollow State, thank you very much!!!!
Tyler
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Old 24th November 2020, 09:26 PM   #5
PRR is online now PRR  United States
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Simpson VU meter repair
Quote:
Originally Posted by rayma View Post
This RC-11 manual has some RC-10 info, but only this much on the meter:
VU Meter: 0-1 ma DC Weston Model 862
.....
Since most such meter movements have a basic 50uA sensitivity...
Where do you see "1ma"?

IIRC, the customary sensitivity was 200uA. (They are not quite as fragile as the 50uA meters found in high-end VOMs.)
Attached Images
File Type: gif RCA-RC11-VU-42.gif (69.3 KB, 55 views)
File Type: gif VU-sensitivity-42.gif (17.3 KB, 53 views)
Attached Files
File Type: pdf VU.pdf (1.67 MB, 11 views)
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