Rejumpering your WPC CPU


This page describes the procedure for rejumpering an early WPC CPU board to accept larger eproms used in later games and software revisions.

It specifically applies to Funhouse and Bride Of Pinbot, but may apply to others.




WMS switched to their new WPC (Williams Pinball Controller) board set with Funhouse. Technically, it was tested in 100 Dr Dude machines, but the first machine to be sold with 100% WPC is Funhouse.

When Funhouse was made, the 'standard' size CPU ROM was a 1 megabit EPROM, such as 27c010 or 27c1001. The 1 megabit chip could 128Kb of data, double that of the largest System 11 CPU ROMS combined!

The WPC-89 CPU could address larger capacity EPROMs, but WMS went with the 1 megabit EPROM likely to keep costs low.

As the programmers started adding more and more features to the games, and started using Dot Matrix Displays instead of alphanumeric displays, the 1 megabit rom image very quickly filled up, and the switch was made to larger chips, such as the 2 megabit 27c020 (or 27c2001), and even the 4 megabit 27c040 (27c4001). The White Water Home ROM (LH5) actually uses an 8 megabit 27c080 (27c801) eprom! As time progressed, the larger chips became more reasonably priced.

The only catch? The early CPU boards were jumpered to only address a 1 megabit EPROM. You have to make a jumper change to address anything larger. Unfortunately, jumpering these boards isn't as easy as making a hard drive a master or a slave, or moving a jumper cap like on a computer board - you have to desolder one jumper, and solder another one in.

Maybe you've seen this table in the front cover of your manual, but had no idea what it referred to:

Display W1 W2
1M / 2M/ 4M ROM In Out
512K / 1M ROM Out In

The table refers to how your CPU board must be jumpered to boot, depending on what software you have installed. The 'display' column indicates the size of EPROM chip being used, the W1 and W2 columns indicate which jumper is to be installed.

Earlier versions of Funhouse software used a 1 megabit ROM image, but as the title was enhanced, WMS moved it to the 2 megabit part.

I get asked about this pretty regularly, so I took some pictures and put this document together.

Now, for a disclaimer

Rejumpering a CPU board involves using a soldering iron on an expensive printed circuit board.

If this is done incorrectly, you risk burning yourself, starting a fire, or damaging a very expensive circuit board.

Many components on these boards are easily damaged by heat and mishandling. They are ESD sensitive.

Many board repair shops will not touch a board that has been previously repaired by an amateur.

If you are not experienced with doing printed circuit board level repairs, you do not need to learn on your pinball machine's circuit boards - find a broken VCR, alarm clock or something else to practice with first.

I am NOT responsible if you burn yourself, damage your game or its circuit boards, burn your house down, fall asleep while soldering etc. You are using the information contained within at your own risk!




Click on any image to open a larger copy in another window

Funhouse - Revision L-2

Here's the CPU board, with the original L-2 ROM installed.
L-9 CPU ROM Installed - but does not boot

(here is where I usually get the phone call...)

Time to pull the CPU board and rejumper it!

CPU Board is on my workbench
An overhead shot of the eprom size jumpers on WPC-89 CPU boards - W1 and W2.

There will always be a jumper installed in one of these positions!

A closer shot. You are looking at the white component in the center of the screen - a zero ohm resistor or jumper wire.
I've desoldered the jumper - you can see where W2 has a dashed line connecting the right most of each set of holes, and W1 has a line connecting the left most of holes.
The jumper has been moved from W2 to W1. The board should now boot!

I carefully removed the jumper and reused it, nothing is stopping you from using a new one - I just wanted it to look more 'original'.

Note the new battery holder - I assure you this is the same PCB. The original battery holder contained 3 corroded AA batteries - the holder was junk and needed to be replaced. Luckily, the batteries leaked no further than onto the battery holder itself.

Don't believe me? Click the picture and it will open full size, and you can compare the serial # label to the board picture above!

Batteries installed

Note the lovely corrosion on the terminals (greenish white goo)

This Funhouse spent the last 10 years in a barn - it's a miracle the corrosion did not continue on to the PCB itself!

Batteries Removed - look at all the corrosion. The parts laying in the holder are the 'pads' that make contact with the batteries. This item must be replaced, it can not be refurbished or cleaned!

CPU board reinstalled. Success! Funhouse is now running the latest software!

At this point, you are ready to play!

Questions? Comments?

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Last updated Wednesday June 13, 2007