Re: Results for Resistance Check on the Control Board; testing a resistor pack?

[Vic Dively]

Thanks Don,
I looked at Appendix B and redid several solder joints.  I'd like to
think my resoldering solved things, but it is probably the fact that I
was reading the pin numbers wrong that caused my problems.  Looking at
the schematics I finally figured that one out.

Now I'm getting 85.3K for U6 pins 29 and 30, with and without U6; just
right.  U3 pin 8 is 1.008M, and the U8 pins 15 and 16 are still open, but
that may be OK.

As far as resistor pack 4, I remember an "incident" while I was
installing RP4, after soldering all the pins, I tried to straighten it
out a little on the board - it wouldn't bend, but I did feel a little
"snap".... so even though I am getting the correct readings for U6 pins
29 and 30, I'm wondering if I possibly damaged some of the resistors in
RP4.  Is there a way I can check RP4?  I tried going along the row,
putting the DMM probes on adjoining pins and moving up the pack.  Some
readings were about 85K resistance, some read short.  

It's on to the front panel.  Thanks again.

Vic KG4HTT


On Wed, 16 Jun 2004 23:52:02 -0400 "Don Wilhelm" <[hidden email]> writes:

> Vic,
>
> There is not much on the Control Board that connects to pins 29 and
> 30 -these are the DOT/PTT and DASH lines and they connect directly to
> pins 17and 18 of P3 (they also connect to 2 resistors of RP4).
> Check carefully for any solder bridges at the pins of P3, the U6
> socket and RP3.
>
> If you suspect U6 itself, you can remove it from the socket and
> check the resistance on the board itself (you should see a high

resistance
> similar to the values indicated in the manual) - use static protection
when
> inserting and removing U6, and put it into the black anti-static foam
(or the
> antistatic tube) when it is removed.
>
> 73,
> Don W3FPR

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[Brian Mury-3]

> Now I'm getting 85.3K for U6 pins 29 and 30, with and without U6; just
> right.  U3 pin 8 is 1.008M, and the U8 pins 15 and 16 are still open, but
> that may be OK.

Pins 15 and 16 are supposed to be >100k - if you're reading open, then
they're >100k! I get about 37M for both of these - perhaps this is too
high for your meter.

> RP4.  Is there a way I can check RP4?  I tried going along the row,
> putting the DMM probes on adjoining pins and moving up the pack.  Some
> readings were about 85K resistance, some read short.  

You often need to take components out of the circuit to measure them,
otherwise you are not measuring the value of the component, but the
value between the two terminals of the component. The measurement can be
affected by other components (imagine two resistors in parallel).

However, a quick look at the control board schematic suggest that you
should be able to measure RP4 in-circuit, and my DMM confirms this.

--
73, Brian
VE7NGR

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