I've got a wide body Williams Contact pinball project that I just set up to work on. It's been in storage for quite some time and is in unknown condition.

Time to inspect the boards first.

It has a system 4 board in it (1D-2001-133-4). This was originally a system 3 game. The original game/flipper roms were still in the game and a couple of them had broken legs. The original scanbe sockets were still present. Obviously, it's not going to work like that.

Time for an upgrade.

I purchased a set of new game/flipper roms which only use IC14, IC17, and IC20. Of course this is the perfect time to go through the boards as well. All connector pins were cleaned and re-flowed. The scanbe sockets were removed and new sockets were installed for the game/flipper roms at IC14, IC17, and IC20. The CPU at IC1 and the clock at IC5 were also in scanbe scokets so those were removed and replaced with new sockets as well.

My main question is this:

Are there modifications that need to be done to the system 4 board to run a system 3 game (Contact in this case)? System 4 already has the IC14 socket to accommodate the new set of roms, but does anything need to be modified, or is this a plug and play adventure?

I understand there are some small modifications to be done on a system 3 board that you are using the updated roms for (add the missing IC 14 socket and converting the selection circuit). But this is a system 4 mpu that already had a socket at IC14. I'm guessing you don't need to do the selection circuit modification, but could be wrong.

I'm thinking this should be plug and play, unless the mpu has issues of its own. Just wanted to make sure first.

Thanks!

Excellent! What are the stock positions for jumpers on a system 4 board? I can't find any info about this, only info about jumpers on a system 6 board, which this is not.

I know that the sound board also has jumpers on it, which shouldn't need to be changed in this case.

I did find brian_G's pinwiki link 4.2.6 states: "A System 4 MPU is backward compatible with a System 3 MPU with no modifications performed." Perfect. Just need to make sure there are either no jumpers on a system 4 or that the jumpers are in the stock positions and I can fire this baby up to see what I've got.

I did also have a spare nvram in the shop so I removed the 5101 at IC19 and replaced it.

There is ZERO battery damage on the MPU witch is great. I did remove the battery holder a well since it's got nvram on board now.

I'm also wondering about the flipper roms.

System 3 games used the "white" flipper roms and system 4 games used the "yellow" flipper roms.

I'm wondering if since this is a system 3 game, that the set came with "white" flipper roms, but I'll actually need the "yellow" flipper roms for it to work properly on a system 4 board.

Is that a correct assumption?

Sorry, that's just ignorant. Game still has to have the same flipper roms no matter the board.

Thanks for the jumper info. I didn't see any, but that doesn't mean they didn't use some resistors in place of them like other boards.

I went ahead and fire the game up. No displays, GI comes on and that was it. Both lights on the mpu come on and stay on solid. Sometimes one or the other will come on and turn off while the other stays solid. So, I pulled out the driver board and just booted the mpu with the same result. After checking out some other threads about issues with new roms, I pulled the 2 new flipper roms that I had gotten from thatpinballplace and replaced the original flipper roms back on the board. Got the proper 1 flash on each led so I put the driver board back in, bingo! Something wasn't compatible with those new flipper roms.

Game is now up and running. There look to be some lamp issues as a couple aren't on and some look like they are twice as bright as they should be, but I'll address that after I order a rubber kit and new lights for the whole machine.

For now, everything else is working after a few small switch adjustments on the playfield, and replacing a broken ring on one of the pop bumpers. Seems like it might be a challenging game with the way the flippers are set up. There's not really a good way to cradle the ball on this one.

So, System 4 works in a system 3 with no modification.

Just finished this one up last night. There was a full column of lights that were twice as bright as they should be and some were on all the time. In diagnostic mode the column of lights all flashed on and off as they should, they were just brighter than everything else. Replaced the associated transistor on the driver board and all is good.

Finished up with a new rubber kit and all new lights throughout the machine. There was one bad lamp socket on the ball save post between the flippers. Contact is now up and running 100%.