[R-390] Measuring Resistance Values

[Bob Camp]

Hi

Ok, I’m guessing we have a typo. 

We’re measuring voltage at the test points rather than resistances. Let’s see, I’ve probably only made about 10 typo’s in this message so far … :) :)

Some of the old VTVM’s had pretty crazy input impedances. It would a bit unusual to find one that was above 10 Meg *and* something you would use in a radio with hundreds of volts running around in it.

Something like a Simpson 260 would be a much lower input impedance device when set up for looking at test point voltages. Simple answer in this case, grab that Simpson and see what it reads.

Bob

> On Sep 2, 2024, at 10:31 AM, Barry <n4buq at knology.net> 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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