(Topic ID: 223525)

Playmatic SS Transformer/General Tech Help (Last Lap)

By zacaj

3 years ago

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  • 2 posts
  • 1 Pinsider participating
  • Latest reply 3 years ago by zacaj
  • Topic is favorited by 2 Pinsiders


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#1 3 years ago

A friend brought me over a Playmatic Last Lap he'd picked up, hoping I could get it working. No idea if anything works, so I wanted to try going one step at a time like I would on bally/williams/etc games. Transformer first, then PSU, the MPU, etc, but not much info available on these.

First thing I noticed was that it still had a european plug on it. Luckily it looked like there were some jumpers on the transformer, so I think it should be convertible to 120v. I replaced the power cord, and tried to find a description of the jumpers in the manual, but it's got nothing beyond a note that it's adjustable for different line voltages. IMG_20180818_190355 (resized).jpg

I found the transformer on the schematic:
IMG_20180818_190348 (resized).jpg

But I'm not having much luck making sense of it. 7V winding for GI makes sense. 10V-0-10V winding sounds like it's used for a two-phase light system like Bally 6803s... I also see an adjustable coil voltage, 28-32v, which is cool.

I assume all those connections on the bottom with the arrows correspond to the plugs on the transformer, but the numbering isn't quite the same, and it's hard to tell on both the plugs on the schematic which connection each label refers to. Examining the wiring, I found two plugs coming out of the transformer wiring harness, one with four wires that seem to correspond to the four wires going into the bottom of the transformer on the schematic (although colors are hard to tell) and one with a lot more wires that seems to correspond roughly to the output wires on the other side of the schematic. So I figure if I don't plug in that connector, I won't have the voltages going into any of the boards, and I can make sure they're all what they should be.

I took the jumpers and moved them to my 'best guess' (pictured) of what the setting for 120v would be, and plugged it in to the wall. Nothing exploded, which is good. I measured the windings on the transformer for the 10Va and 10Vb, and got 11VAC on each, which seemed good. 7v windings give 6.5VAC, white to ye-rd gives 30.5VAC. Everything seems good so far, looks like I guessed right regarding the jumpering. But!

with the game off, measured voltage at the service outlet. 120VAC, as expected. With the game on: 210VAC. What? And I look at the schematic. Why is the service outlet wired through a winding of the transformer? It's a more US-style plug too, not european style. Very confused. Can anyone explain what's going on with that?

Does anyone have a Last Lap or comparable Playmatic SS machine working on US voltage levels they could check the jumpering on?

Any other tech tips as far as setting up and testing the game/boards?

#2 3 years ago

Reading more of the manual, it claims the MPU has overvoltage protection, which is cool. Not sure how well it works, but that combined with getting the proper AC voltages out of the transformer convinced me to just plug the transformer output plug in and see what happened. Usually I'd like to disconnect everything and then connect bit by bit, but there's no overall wiring diagram, so it's nearly impossible to actually figure out what any plug does. I was able to make out that the MPU gets the two 10VAC feeds sent directly into it. There's no rectifier or regulator board, the MPU does a half-wave rectification and then regulates it down to 5V (and -5V for the weird rom chips it uses) itself, so there wasn't really any way to test voltages supplying the MPU. I would have pulled the HV fuses, but since the playfield isn't even in the game right now, there's no coils hooked up, so that should be safe. The controlled coils are all just AC, energized by a 'relay board' in the back. The non-controlled ones are DC, and function just like they would on an EM:
IMG_20180819_121900 (resized).jpg

Also of note is the drop target reset coils. Like many EMs, they're powered off line voltage to give them enough power to reset the giant drop bank on the game. But unlike most EMs, these seem to be rectified! So probably looking at ~140VDC powering the drop target reset, wow. Strangely it looks like the rectifier is hooked up backwards on the schematics, not sure what's up with that.

Anyway, I turned it on, and amazingly it went through the self test sequence and got to attract mode! Some scores are flashing on the displays, at least. The backbox GI is dead. Circuit seems to be just fuses and connectors though, not controlled or anything. None of the controlled lamps on the backbox seem to be working, but I'm not sure what they even are since I don't have a backglass, so no way to say whether they're supposed to be on or not.

Next step will be to install the playfield and see if it powers up.

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