Williams Slugfest

In-Home Repair

Peoria, Arizona

Switches were intermittently registering. ¬†You couldn’t always select
the desired pitch even though it was set up that way in the
adjustments. Would sometimes throw the wrong pitch . Some of the out
switches wouldn’t register until you pressed them up further. Home run
switches wouldn”t always register.

Everything worked 100% in switch test.

So after swapping MPU’s, checking the optos, checking the opto
boards( lm339 and diodes and resistors), checking the 7812 12V
regulator and cap and various other checks I found the culprit under
the control panel.

On slugfest the diodes for the switches on the control are on a
seperate diode board (all of these diodes had already been checked).
This means that every switch under the control panel only has 2 lugs
occupied and the third is empty.
Well someone has accidentally put the lamp matrix wire (forgot if if
was a row or column) on the empty switch lug so the lamp voltage was
feeding into the switch matrix (but only when the lamps are on, so
that explains why the issue wasn’t persent during the switch test).

So two lessons learned here.

#1 always physically check every single switch before checking for
exotic fixes
#2 lamp power into the switch matrix will cause this weird hesitation
on the switch matrix, but was not causing any false hits (at least
none that I could tell, except maybe the wrong pitches)