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

[David Wise]

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
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html