Check the PinWiki System 11 section:

https://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#System_11

Code 8 seems to mean: "General system failure. Check the 5VDC power supply as well as the integrity of game ROM 2 at U26."

Alternatively: An eight displayed during memory chip test (using the CPU board switch SW2) indicates that the blanking circuit is functioning properly.

If you remove the board from the game, does it go back to zero? When you booted it to a zero code, was that with the game power supply, or an external (ATX?) power supply?

Okay, so if you have the board installed, with only J17 connected, you get an 8. If you pull the batteries, you get a 0?

I wanna say I fixed a High Speed with a similar problem, and I had to swap the RAM chip at U25.

Scroll down the Wiki page a little further to the section that starts with "An U25 RAM failure". You may want to check some components first.

I'm also assuming your coin door is open when you're running these tests? Otherwise the Memory Protect switch will cause problems.

Check you memory and your rom sockets. I have also have a defective display that always showed 8 but was fully booting and playing fine.

The difference between "0" and "8" is the MSB of the 4-bit input to the 7447. The MSB in REV- boards is tied to ground. The MSB in REV-B boards is connected to the BLANKING signal through W16. Your board is a REV-B with W16 installed and therefore the MSB is connected to the BLANKING signal.

01_board.jpg
02_blanking.jpg
03_digit_input_msb.jpg

Check the ~BLANKING signal. There is a test point just above U20-2 that is connected to U20-2. It should be LOW when you see "8" and HIGH if/when you see "0".

Alternatively you can test 1J21-2 or 1J22-2. If you test at this point then it should be HIGH when you see "8" and LOW if/when you see "0".

If the signal matches the state then you likely have an issue with the blanking circuit. The Leon does not test the blanking functionality. The blanking circuitry keys to the constant strobing of the display (tied to bit 2 of the strobe input). If the processor is executing correctly and the software is correct then the software needs to continually strobe the display and will cycle through all 16 strobes (4 bits).

If you are using a 27128 then double the actual 2764 image. Since W2 is installed on your board you will need duplicate the image as the A13 address is active. If you remove W2 and install W3 then you can place the 2764 image in the "upper" half of the available storage as the A13 address line is tied to VCC with W3 installed.

If you are using a 27256 then quadruple the actual 2764 image - double the double. If you remove W2 and install W3 then you can place the 2764 image in the 4/4 "slot" of the available storage. The 27256 has $8000 bytes of storage. The 2764 image is $2000 bytes. Place the image at offset $6000 in the available $8000 bytes of storage. You will need to do this as A13 (pin 26) and A14 (pin 27) are tied to VCC with W3 installed.

It might not be in the manual, as sometimes later software revisions could require a larger EPROM chip. You can typically guess the proper EPROM chip based on the size of the binary image. The 32K image is a 27256, a 16K image is a 27128 and an 8K image is a 2764. At the time, a 2764 was likely notably cheaper than a 27256. These days if you can make a 27256 work (be sure to quadruple the image), it might be easier to just stock the one size of chip.

For High Speed:

• U27 should be 27256
• U26 should be 2764 but can be 27128 (double) or 27256 (quadruple)