Ok so I’m getting some strange behaviour on my Medieval.
on start up after not playing for a few hrs I’m getting the same switch errors coming up.
left out lane left return lane
right out lane right return lane
right troll left loop high
left top lane
right bank top.

It’s these same switches every time. I do the switch test and remove the errors and they don’t come back until the machine has been off for a substantial amount of time. It does throw up a row 1 ground short every now and then at start up but goes away. Errors always stay.

Ive checked all switches and seem to be fine. No loose wires. Replaced u20 u13 u14 as per a few forum suggestions.
Any other ideas?

I’ll just add that once I clear the errors the game plays perfectly. No switch problems at all until the game has been switched off for a while. Usually takes about 4-5 hrs of the game being before The errors will turn up again. I can switch it on after an hr or two and no errors. One thing it did today was the left popper fired a few times after start up.

Thanks. I’ve been chasing the ground short for a while. It’s really intermittent so hard to find.

I’d checked all the switches but I’ll go through it again to make sure.
Oh and yes. Original.

No corrosion.

I’ve checked all wiring, diodes and switches three times just in case I’d missed something.
Frustrating thing is this morning for the first time it started with no errors. I’ve did nothing to it yesterday that could have changed that so it’s baffled me more.
Because it would only have the errors after a long period (6 or 7 hrs) of no use It has been like the car that won’t start cold. Fine once running and you could start it again when still warm but as soon as it’s cooled down the problem returns.
See what happens next start I guess.
I must say I haven’t seen the ground short for 3 or 4 days now.

Thanks. I’ll try that next time it pops up. Maybe I’ll tap a few switches and see if I can get it to pop up.
Being the row 1, would it definitely be in that row? Maybe I’ll just change all those switches out.

That’s the thing the switch errors aren’t all in the same row. The ground short when it appears is alway row 1 but very intermittent. Then when it does pop up it’s for 5 seconds and disappears.

I haven’t had a chance to do much with it lately but I did catch this behaviour at start up.
I went straight to switch test and had 2 ground shorts. Within a minute they slowly disappear without me doing anything.

So I pulled the opto board out and on close inspection I notice a tiny bit of the dreaded green fur on a leg of one IC.
Decided to pull all three and glad I did. Two had it under them.
Cleaned it all up and replaced ICs. Cross my fingers it seems to have stopped the ground shorts.

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