[R-390] R-390/URR - Resistance Checks

[Barry Scott]

That makes sense and is just what I did.  I just haven't seen anything
that shows what resistances should be at a given plug.  Maybe I just
haven't seen it yet.

Thanks,
Barry - N4BUQ

On Fri, Nov 22, 2024 at 10:57 AM David Wise <d44617665 at hotmail.com> wrote:
>
> I think it means that if you are measuring a receptacle contact (not something else), you do it by pulling out the plug then probing the exposed contact.
>
> Dave Wise
>
> ________________________________
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on behalf of Barry Scott <72volkswagon at gmail.com>
> Sent: Friday, November 22, 2024 8:43 AM
> To: R-390 Mailing List <r-390 at mailman.qth.net>
> Subject: [R-390] R-390/URR - Resistance Checks
>
> I've been measuring the resistance values at the various pins at V701
> and I am wondering about the proper way to do this.  There's a note at
> the bottom of Figure 82 and Figure 83 that states:
>
> "RECEPTACLE RESISTANCE READINGS ARE TAKEN WITH PLUG DISCONNECTED."
>
> Is this supposed to mean that if I'm measuring the resistance between
> the tube pin and GND, that the plug for a given module (e.g. IF
> chassis, PTO chassis, etc.) should be disconnected?  If so, I have
> always gotten values that are very different for some/most of the pins
> that way.
>
> Of particular interest is V701, Pin 6.  Figure 83 shows that to be
> 40k.  Without P715 inserted, that value is 0 on my PTO.  If I reinsert
> P715, then I get 59k.  From what I can tell, an additional 19k is at
> J155A to GND which (I believe) comes from R623 and R618 in the power
> supply.  If that's the case, then the resistance at V701 Pin 6 should
> be R702 (33k) + R703 (2.2k) + 19k from the power supply which totals
> 54.2k so I don't know how Figure 83 shows that as 40k.
>
> Is it possible some changes were made in the circuits that were not
> updated in Figure 83?  If not, then I'm pretty puzzled.
>
> Thanks,
> Barry - N4BUQ
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