TZ opto board row shorts.

[Wombat]

Hi All,
My TZ is reporting complete rows being shorted. I think I’ve isolated it to the opto board. When unplugged the switches are fine. When plugged in it reports multiple rows as shorted. When I take out the 339s (I’ve socketed them) it reports row 4 only as being shorted.

Not sure where to go from here so any guidance greatfully received.

thanks in advance,
Simon

 

[DRD]

I had a broken track on my TZ opto board. Needed a magnifying glass to spot it

 

[Wombat]

I had a broken track on my TZ opto board. Needed a magnifying glass to spot it

Thanks, so this also registered a row short ?

 

[DRD]

I can't remember what the fault was, it was years ago. Opto boards can get hot so well worth looking at at connectors/ dry joints/ tracks etc.

I checked everything for continuity with a multi meter

 

[Wombat]

Thanks for your suggestions.
I have been around with a MM to checked continuity as far as I can tell. I’ve also replaced all three 339s. As mentioned, the shorts don’t appear when I disconnect the main jumper.

 

[Pick Holder]

Just remove the clock using the plugs that go into the back of it.

If the short goes - then it is in the clock.

There is a chance you could have a bad connection on one of the tracks underneath the socketed chips.

 

[pinballmania]

I think the OP is referring to the 10 opto logic board not the clock board.

Just because the unplugging of the 10 opto board makes the ground short disappear doesn’t mean the problem is on that board.

You need to put it in switch test, unplug all the plugs for switches to the cpu, and then test all switch input combinations by linking each column with each row in turn with a wire link. Only if each combination gives one switch closure can you say the cpu is good.

It doesn’t take very long. Just connect to one row then move the wire along the 8 column pins. Then repeat on each row.

 

[pinballmania]

If you see a fault on the switch matrix whilst doing this, then most likely the 2803 is blown on the cpu.

 

[Wombat]

If you see a fault on the switch matrix whilst doing this, then most likely the 2803 is blown on the cpu.

Thanks for this. I have tested with this method with no issues.

 

[drhex]

You can send me the 10 opto board and I’ll test it in mine (and repair if needed).

 

[Wombat]

Thanks so much for the offer ! I’ll pm you.