On 9/27/2010 11:40 AM, Karl Townsend wrote:

(...)

Yep, this is the point everybody missed. The operator panel is all
soldered up and I don't want to take anyting apart in there. it would
ruin it. I don't need to just trace a wire from one end to the other,
I need to know which wire is connected to which switch.

Well, not *everybody* missed the point.

Quoting me:

Does your ohmmeter have a 'beep' continuity mode?

(This goes a lot faster than my explanation implies.)

Start by shorting the two probes together to confirm the
meter will beep properly.

Place one probe on pin 1 and move the other probe to pin 2 - 50
in sequence. Record all beeps. Move your probe from pin 1 to pin 2
and repeat your scan with your other probe.

If a pin beeps to any other pin, write that down.
'Pin 5 to pin 32' for example.

Eventually you will find a pin that beeps to a lot
of other pins. (Often, many of the even - numbered pins or odd -
numbered pins.) If these pins also beep to a ground point on the
control panel, you have good evidence to support the theory that
you found your ground connections.

Confirm this by switching to normal 'ohms' mode and check the
'beeping' connections once more. You should see that there is
no difference in resistance between 'shorted probes' and your
suspected connections. Remove any connection from your list that
appears to exceed that resistance by say 0.7 ohm or more.

Example: With probes shorted together, you see that the meter
reads 0.2 ohm. All the valid connections will read no more
than say 0.9 ohm. (Practically speaking, your valid readings
should also be in the 0.2 ohm - 0.5 ohm range).

A pin reading higher resistance should be dropped from your
list (unless it is just a dirty connection that you can polish
and bring under 0.9 ohm).

Use alligator clips to connect your beeping ohmmeter to your
ground connection and hold the other probe in sequence to each
of the pins that did not beep.

Press each button on the control panel till you hear your meter
beep. Write down the pin number and button logo.

You can run this inspection in about 1% of the time it would take
to build your terminal strip.

That is how I do it.

Unquote.


--Winston