(Topic ID: 269467)

Williams Sys3 / Lucky seven - severely burning driver board


By Edenecho

40 days ago



Topic Stats

  • 9 posts
  • 6 Pinsiders participating
  • Latest reply 38 days ago by Inkochnito
  • Topic is favorited by 1 Pinsider

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#1 40 days ago

Hi! I hope someone familiar with system 3 boards or boards in general could give me some insight on what might have caused this catastrophe :O
Short version:

I picked up a Lucky Seven (ss),cleaned it and made sure all fuses were replaced with correct value. It booted and seemed to work except the different reel combinations did not light the corresponding lights (only for a couple combinations), and dropping the targets did not award the value. I cleaned the reel circuit boards with some rubbing alcohol, without much change. Upon troubleshooting with the game in-play, suddenly i notice (and heard) the center reel coil was being locked on by itself. I pressed a switch to advance it, and it got unstuck. But at that time it was REALLY hot. I turned off machine and let it cool down. Then i turned on and started a game to trouble shoot. Now the lights were all wonky, blinking or being on when they shouldnt, and the coil at intervals locked on again. Thats when we started smelling burned electronics. Turned off machine, opened the backbox and HOLY CRAP, all of the...resistors (?) / Capacitators on the MPU board was literally black and melting, looks almost like it was fully burning!

Very severe, and i am kinda scared because I dont know what might cause this extremity?
Dont want to plug in a new rottendog board if the same might happen to it.
If you look at the pre toast photo, the column that burned seems a little brittle, so maybe they were already failing`?

The reel circuit boards should not affect the reel coil, as it only indicates what lights and value should be lit. Can there have been failing components on board from earlier, making it lock on by itself?

Any help appreciated!
Morten
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#2 39 days ago

It seems you may have some interconnect problems.....
Not saying this is the main cause, but it could be one of the causes.

I would also recommend adding fuses to the bridge rectifiers in the back box or use one of my Bridge Boards.
Just to prevent your game going up in flames is case of a rectifier problem.
Look on my website http://www.inkochnito.nl for more information (click on the Bridge Board image).

Peter

Pre-Toast (resized).jpg
#3 39 days ago

That's the driver board not MPU board.

First thing is check the DC output voltages of the power supply board.

Next thing is replace the 40 pin interconnect connectors. A lack of proper communication between the MPU board and driver board can cause things to lock on and burn up.

Your driver board is an early one and needs some updates.

One or more of the 6821 chips may have gone bad.

#4 39 days ago

The feature lamps strobe 18v quickly. What can happen is when the CPU gets locked up it can cause the lamp column drivers be permanently on instead of strobing. This makes the resistors heat up and turn into wire wound toasters. The board will burn and they can desolder themselves. Blanking is supposed to save you from this, but it is obviously not fool proof.

The busted pin in the interconnect pointed out above could be the reason the CPU locked up on the lamp column drivers got locked on and burned your board. I would replace the 40 pin interconnect the lamp column resistors (use 27R 5W) and see where you are.

The picture makes it look like one of the 7408 chips above the resistors may have a crack in the case. If it really does it needs replaced. Otherwise the damage might just be cosmetic to the plastic case of the chips.

#5 39 days ago
Quoted from Inkochnito:

It seems you may have some interconnect problems.....
Not saying this is the main cause, but it could be one of the causes.
I would also recommend adding fuses to the bridge rectifiers in the back box or use one of my Bridge Boards.
Just to prevent your game going up in flames is case of a rectifier problem.
Look on my website http://www.inkochnito.nl for more information (click on the Bridge Board image).
Peter
[quoted image]

Yes thanks, my boards are on the way from you as we speak!

#6 39 days ago

Thanks for the answers, it is helpful into understanding what is happening. I changed the title to "driver board" now,not MPU.
As there are severely burnt components, and also an early version of the board and the horrible interconnector is there (the game had been in storage since 1989, until i picked it up some weeks ago), I am thinking of just doing the safe thing and buy a new combo mpu/cpu board.

Any thoughts on these three, which seems to be the options?

PinballPCB:
http://pinballpcb.com/products/williams-system-3-thru-7-driver-board/ (there is also an mpu there,for a bundle)

Rottendog:
https://littleshopofgames.com/shop/boards/rottendog-boards/mpu327-williams-pinball-machine-system-3-system-4-system-6-mpu-and-driver-combo-board-rottendog/

Pinball Dreams all-in-one board:
https://www.pinball-dreams.com/flipper-pinball-flipperautomaten-modding-shop/verschiedenes/all-in-one-nw7.html?fbclid=IwAR2r3whhKWV9lasiLbNS0t3DRrAoN0_osFD5Dy9AhAfLDkp1K-aWHDE-YHY

inkochnito I have the bridge and the solenoid board coming from you as mentioned, are those boards compatible with the reproductions above? I guess your boards are an added safety measure outside those boards in any case?

#7 39 days ago

Pinball PCB is closest to originals and my choice.

Pinball dreams would be my second choice (and possibly first choice if I need to replace the sound boards as well).

Third choice would be original WMS boards.

I wouldn't buy the RD board at all. There's issues with some system 7 games with that board and you can't change the software on it if you need to (for custom versions for instance).

#8 39 days ago

Those resistors are a very common failure point, the circuit drives them VERY hot even when everything is working properly. The conventional fix is to replace them with much higher wattage ceramic resistors. You can also swap the driver transistors with mosfet's, which cools them down considerably.

Of all the choices, I'd suggest the PinballPCB above the others. Already has the mosfet change integrated in, among other things I really like about his boards.

-Hans

#9 38 days ago
Quoted from Edenecho:

inkochnito, I have the bridge and the solenoid board coming from you as mentioned, are those boards compatible with the reproductions above? I guess your boards are an added safety measure outside those boards in any case?

My Bridge Board is compatible with all games from System-3 up to System-11A.
It does not matter which System is in the game, Williams, Rottendog, anything....
The fault is in the wiring of the cabinet/game.

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