[R-390] Measuring Resistance Values

[Jacques Fortin]

Hello Barry,
A modern DMM with a 10M input can make differences only with the read
voltages, but not for the resistances values.
The Allen-Bradley resistors used during your set construction are about 70
years old now.
Not surprising that they have raised in value and need to be changed.
The only good news is that most of the Sprague "Vitamin Q" used within
should still be good if they show no signs of internal oil leaks.

BTW, what is the serial and contract number of your set ??
Mine is a 14214-PH-51-93 sn 2074.

73, Jacques, VE2JFE in Montreal

-----Message d'origine-----
De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
part de Barry
Envoyé : 2 septembre 2024 10:31
À : R-390 Mailing List <r-390 at mailman.qth.net>
Objet : [R-390] Measuring Resistance Values

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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