For the last 6 months or so, I've been working on a project game that has been passed around upstate NY like a bad penny. It's a 1978 Playmatic Last Lap-- very cool and unique playfield layout, and the (few) videos on youtube of gameplay look like fun. It appears that working playmatic SS games in the US are frighteningly rare.

With scant, almost non-existent documentation, this project has proven difficult. A couple of friends and I have spent more time troubleshooting these board (and their totally obsolete parts) than I care to talk about... but I finally have some success to report. Last week, I was able to secure some replacement boards from someone who parted out another playmatic machine, and using the replacement MPU plus the decoder and thryistor boards that we have rebuilt, I was able to get the game to complete its boot sequence, it goes into attract mode, allows me to add credits, and start a game!

There are still however, issues that need to be overcome...
- upon starting a game, the ball is kicked into the shooter lane, but the kicker remains locked on.
- The drop target bank doesn't reset
- the flippers don't work
- the playfield switches don't work.
- the scoring displays either don't work at all or display gibberish. I know the voltage from the decoder board is good, as it operates the credit and ball in play displays.

I suspect that the first several issues may relate to the bridge rectifier under the playfield, which I will test tonight and replace as necessary.

Anyway, I just wanted to share some of the successes, I'm happy that it finally seems to be moving in the right direction.

If you've got any other ideas for things I should be looking at and testing, I'd welcome any and all advice.

It’s more alive!

Not sure what I jiggled, but I jiggled something, and the game started working! No displays, but everything on the playfield is working! I’ll have to track down whatever wire is broken and keep at it. There’s power to the displays, so I’m unsure on where to turn next with those.

Cleaned up the drop target unit last night and it’s working much more smoothly now. Stripped the topside of the playfield to shop it, and had to order the lane guides from Europe- shipping was more than double the price of the parts!

Still stumped on the displays and would welcome any ideas folks have.

Thanks! The displays operate on 10v. Very different from the US manufacturers who were using 170+ volts on their displays. Yes, it has electronic sounds. There's not much to the soundboard... it really only makes a half-dozen different sounds. The data for the displays comes from the decoder board, which is otherwise working (it's been rebuilt with all new caps and went through all the rest). There's a separate 4511 IC for each of the digits on the displays, and it's REALLY unlikely that they have ALL failed. The displays *are* getting power... so I'm a little puzzled as to why all I get is some random, occasional gibberish on the displays. It's possible that the individual digits of the displays aren't getting power.

With the second board set I picked up, I have four spare displays. I"m going to swap mine out for those this weekend and see if the condition changes. I may end up having to risk ruining one by tinkering with a test rig to see what I can get to light up. Hopefully it doesn't come to that.

Hush up Lonnie! You're just jealous of my awesome machine! (the couple of parts I ordered from a vendor cost me almost as much as what I got the machine from you for... and the boards cost me more, so I'm at the point where I'll probably always be underwater on this machine, but I'm still going to see it through).

Yes, I have one. I wouldn't consider myself an expert in using it, but I can sort of fumble my way through it. Part of the challenge is the lack of documentation on the machine. I've learned that the built in test probe is isolated such that I can poke around with impunity, and as long as I don't bridge two contacts, I won't hurt anything. I'm less sure of preventing harm using the logic probe.

I didn't see this until just now. I'll check on the chip numbers and report back.

I did do a bit of an experiment last night. The back of the display boards are marked with what each pin controls (if nothing else, I have to thank whomever at playmatic thought to do this... there's no documentation, but at least things are well marked and I'm not guessing!). When I hook power to the displays with my test rig, I can make each segment light. I know power is getting to the displays... so it simply has to be an issue I missed when rebuilding the decoder board.

I discovered something neat (but tough to achieve) in the ruleset. If you knock down all of the targets *except* the black ones, you get a special. If you knock down *only* the black targets and leave the rest standing, you also get a special! I've got some light sockets coming from Marco today, so I'm going to replace a bunch under the playfield-- several of the sockets for the feature lights are shot.

Yup. I've spent more time staring at the back of that board than I care to admit. Everything has been reflowed. Everything that I know how to test has been tested.

I'm decent at doing repairs when I've got some instruction or documentation to work with. Figuring this stuff out with no documentation isn't my strong suit, and part of the reason this project has taken so long to get working and why 3 other projects have been both acquired and restored in the same time.

Thanks! Time and persistence.... the actual repairs haven’t been that horrible once I figured them out. The irreplaceability of the boards has made me a little gun shy, so I proceed with extreme actuation. Lol.

I’m down to just a couple of feature lights not working, so I’ll be tinkering with the thyristor board this weekend.