My TZ has developed a strange switch matrix problem on one row of optos. Essentially they flicker in Switch Edge test, when just standing in front of the machine.

The whole row doesn’t appear to activate, so I don’t think it is a short. The wiring and the mini playfield also hasn’t been touched which makes me think it’s not that (though it could be I suppose). I’ve owned it 4 years and the batteries have been off the board (and lithium) in all that time, so I don’t think it’s MPU corrosion either?

Sometimes it doesn’t do it for several minutes, other times it does it as often as the below video:

When it plays up like this it means the ball drains prematurely from the mini playfield because the game “sees” the mini PF exit opto trigger, so it’s quite annoying.

All of the optos on the row work, and activate when tested with my finger. The problem doesn’t seem to affect the other optos or rows. Only row 6 seems to be affected.

All of the optos on that row (and everywhere else) work, as in they trigger when I put my finger in front of the receivers etc.

I’ve pulled the 10 opto board (I assume this is what handles all these optos?) and it doesn’t look obviously damaged, but the solder looks a bit dodgy too to my untrained eye. The cap doesn’t look like it’s leaking? I cleaned all of the connector pins with a fibreglass pen and isopropyl but it’s made no difference. Are these boards prone to failure?

One other thing to note - and it might be my imagination - but I swear I can hear a high pitched noise around that area of the playfield, which might be the board itself? I can’t be sure of this though.
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Thanks @coyote. There is also Clock Hour on that row, not seen on Switch Edge test. I did initially power up to a Clock is Broken message which went away when I went into the rest menu (all clock optos tested fine)

Would a failing opto do this to everything on the row?

Interestingly it blinks whatever is activated - so the optos obviously, but also switches like Centre Trough if there’s a ball there.

Following this I removed the connectors from J208 and J206 and reseated them and the problem seems to have gone away, for now.

Very strange. It does look like the 10 opto board has got nothing to do with it though.

Not sure what state open and closed is on Switch Edge test..

It flashes the optos on that row that are normally closed (?), which is mini PF exit and right ramp I think? Trough prox is normally open (not shown on edge screen) unless metal ball present.

But if there are balls in the trough, so that Centre Trough and Trough Prox are shown on the edge screen, then it will flash those too.

It doesn’t flash any switch that isn’t closed - opto or otherwise.

Thanks again Coyote

I followed @pin_guy’s advice earlier and had a look at J206/7 and J208/9 (I can’t remember which pair they were on). There wasn’t an obvious problem with the connectors or the wiring, but after I removed them and plugged them again I went into Switch Edge test and didn’t get any phantom blinking.

I left it on that test screen for 45 minutes without any phantom activations so at the moment I’m considering this fixed.

Maybe I ought to get someone to repin those connectors though.

Thanks for your help!

Annoyingly I ordered a replacement 10 opto board thinking that was the source of the problem. Don’t know why I thought that, initially assumed that whole row was optos (thought the trough switches were, ala Stern)

The batteries have been off the board for all the time I’ve owned it (~4 years), though it’s possible it has/had corrosion from the previous owner. I don’t honestly know if it’s the connector or the wiring, since neither looked wrong - the blue/white wire was in the connector (I didn’t wiggle it though). All of the connectors are IDC though, quite possibly originals.

Still, 45 mins on Switch Edge test with nothing activating counts as a resolution in my book.