I'm in the process of putting a TAF back together. I was getting opto errors on two optos: Bookcase 3 (#55) and Thing up (#85). All other switches, mechanical and opto, worked fine. I started by replacing the Thing opto, but it was still showing as being bad. Removed the LM339 ICs from the opto board under the playfield and replaced them with sockets and new ICs. Going into the switch levels test now, it continually cycles through all optos along with #24 (Always Closed). Strangely though, if I go into the switch edges menu, now all of the book case optos activate fine as do all the other optos except for Thing up - that one still tests bad. What would cause that strange behavior in the switch levels test though?

During testing I did unplug all the switch row/column switches from the CPU board and they started freaking out (same behavior as I described above in switch levels test), but I powered the game off and pulled the batteries so I'd have thought that would reset any issues that may have caused.

Not sure, but I believe so - it's a replacement board I bought from BAA. Both the original and the replacement test bad for Thing up, so it seems likely that it's something other than the opto (or it's a heck of a coincidence). I have the board hanging and was manually trying to activate the switches but no difference. Both switches are getting power to the transmitter (can see the glow when viewed through a digital camera).

Kyle

Hmm, something seems really odd. I swapped the two row wires on the IDC connector that plugs into the Thing opto board like you suggested. When I booted I still got the switch up error, but when I went into switch edges and tested, both optos seemed to be working fine (just opposite of where they should be obviously: up was 84, and down was 85).

So I switched the wires back to the way they are supposed to be and now the up one isn't working again. What would cause that behavior?

Kyle

Thanks. That's pretty much where I'm at too. But I'm not sure how to proceed with the switches. Why would both work when I swap the wires but when I put them in the right place the up opto doesn't work? I'm not sure where to look for that problem.

So right now I have been testing with a business card. The opto board is all wired up but not attached to the Thing assembly for ease of reaching it. When the IDC connector is wired correctly the opto for Thing down (sw 84) opens when the beam is broken by the card, but switch 85 (Thing up) does not. When I pulled the two row wires on the Thing opto board IDC connector and reversed them (I.e. put the wht/yel one where the wht/grn one was and vice versa) both opto switches worked. If the up opto switch.itself was bad I'd expect it to consistently fail, not work when the wire for rows 4 and 5 were swapped on the IDC connector. So that's where I'm currently stuck.

No replacements of the opto on Thing - I ordered a whole new 2 opto board from BAA to replace it completely since it wasn't that horribly expensive. But both boards (the original and the replacement) act the same way so I'm thinking the problem isn't the opto but something else.

I did swap out the LN339s on the 7 opto board under the playfield - installed sockets and added new chips. Prior to doing that both Thing optos were showing as being bad as was one of the book case optos. After I replaced those chips two of my 3 opto problems cleared up. But other than that, no electronics were replaced anywhere.

HighSpeed1: Yes, sorry I didn't see the wiring info you had posted before. Mine is the same as yours

Terryb: No, I have not tried it several times. Good point I will try it again today and verify that I get the same results. One thing I notices is that the end of the molex where the wires attach was kind of "crushed" like someone may have squeezed it with a pliers or something at some point. This would be where the row wire for the up opto connects. So I thought this was probably the issue, but reseating it with a proper IDC insertion tool didn't help and when I swapped the wires the other one worked fine like I said. Still, I suppose I could replace the whole molex just to be safe.

Regarding the switch levels, what I mean by that is that when I go into the switch levels on the test menu (T.2), the game starts cycling through the switches and alerts/displays them in the following order: 24, 53, 54, 55, 56, 57, 82, 84, 85. At first I thought this was a problem since I didn't recall this test working this way before, but after looking at the manual I see it is just cycling through all the switches that are closed. Makes sense for the optos, except that both 84 and 85 should not be registering as closed at the same time.

Arcade: Yep, I've checked that a bunch of times as I've already made that mistake in the past

Thanks a lot for all the responses. This project has really been a pain but I am so close now. I truly appreciate all the comments because as one person pointed out, when you're trying to troubleshoot these problems there really are no bad ideas.

Anyway, I think this has to be some kind of wiring issue. First I tried switching the wires around like I said I did earlier and this time it worked both ways. Then I removed the Thing assembly from under the playfield and just held it in my hand with the wires connected. When I did that and booted the game I had no switch errors and the Thing test registered both optos properly. But as soon as I installed it back under the playfield the up opto switch is stuck closed again.

At this point I'm not really too sure what to do other than try using a new IDC connector in case the "crushed" end of the original is somehow causing these intermittent issues. Unless anyone has any better ideas based on what I've been able to describe.