I have recently got a Roadshow going that had been sitting for a number of years with a range of faults with an operator.

Played fine for 10 games once i got it going, then had a shutdown mid game and got a ground short error.

Replaced U20 and U23, problem fixed....for another 15 games, then same thing has just happened.

So I assume there is a loose/stripped/kinked wire somewhere (presumably from a coil or lamp) that is shorting through a switch or switch wire and taking out the U20 and U23 chips- is this correct?

Does the fact that it takes out 3 rows (5 ,7 andmean anything - ie: should i be looking at switches and wiring associated with those 3 rows, or could it be any switch.

I have had a reasonable look, and most switches look OK, and coils that are mounted near switches don't have any obvious loose wires near a switch wire.

Anything else i can look for, or quick tests that could narrow the search down (i am thinking not, since the problems appears very intermittent)?

Once it happened when i had 3 balls locked and preparing for multiball, the next time it was going for the blast zone - so different coils/switches at work both times.

I dont have any other wpcs games. Have spares of all other boards except mpu for wpcs.

To me, it is a board problem, caused by an intermittent wiring issue - if that makes sense?

Removing all the switch row and column plugs form the MPU - problem remained, so i replace U20 and U23 (now socketed), and problem disappeared for another 15 games or so. Then the game reset mid game (just as i hit the blast zone - although the previous time was starting a mutiball), then came up with the GND short error again.

So to me, i am assuming there is a wiring issue causing the problem, maybe there is an intermittent board issue though? That said, the board itself looks pretty good, no corrosion or previous work i can see.

Both times the reset and error occurred mid game was when the shaker motor was going - this may be pure coincidence, however i do wonder if the extra vibration is causing an intermittent short somewhere - keeping in mind the shaker has gone off plenty of times with no problem.

Ha ha -yes the smiley was row 8, followed by ).... nice pickup!

The only other further information i can think of was i first replaced u20, and the GND short error disappeared, however no switches in column 7 worked - which led me to replacing U23 - then it all worked fine. So i paid extra attention to checking all the switches and diodes and coils near those column switches to see if there was a leg of something that might be shorting....with nothing obvious.