[R-390] Measuring Resistance Values

[Glenn Little WB4UIV]

Carbon composition resistors drift up in value as they age.
You can leave as is if the radio performs well.
You can replace with modern carbon film, metal film or others to get the 
voltages back where they were designed to be.
The performance may improve and tube life may be extended.

Glenn
WB4UIV

On 9/2/2024 10:31 AM, Barry wrote:
> Did Collins specify what input impedance a meter should be to properly read the resistance values in the manuals?  I did see where a TS-352 was mentioned but that's selectable between 20,000 ohms/volt and 1,000 ohms/volt.
>
> I started checking the RF Deck in my R-390 and, starting with V201, I noted a few values that are significantly high.  I was using a modern DMM with 10M input impedance so not sure if that could be the problem but I doubt it would account for that much difference but who knows.
>
> The voltages were off a bit as well but not nearly as much as the resistance values.  I suspect the radio will still work with wacky voltages but the R values really have me thinking I have work to do.
>
> Thanks,
> Barry - N4BUQ
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-- 
-----------------------------------------------------------------------
Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
Amateur Callsign:  WB4UIVwb4uiv at arrl.net     AMSAT LM 2178
QTH:  Goose Creek, SC USA (EM92xx)  USSVI, FRA, NRA-LM    ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"