So I’ve hit an issue where running the cabinet with the Stargate boardset installed, crashes with the ROM board error code 1-3-4 (the display counter flashes 1, then 3, then 4 in a repeating sequence until it reboots).

According to the manuals this represents a RAM error (the one) in RAM row 3 (the 3) at chip 4 (the 4)

So I’ve tried replacing the RAM with a new chip and even swapping the chips around with earlier in the sequence (Row 2 for example) memory chips but the same error seems to persist.

What I’m now thinking, and from reading a number of good blogs including this one here on a Williams Joust restoration:

Is that actually the fault is being caused when the power supply is under load, not having enough power to power all the RAM chips and hence the last in the line (*or could be the first in the line, not sure!) doesn’t get a high enough solid +5V so an error occurs.

Luckily one of my acquisitions from a fellow restorer included an un-used Williams Power Supply rebuild kit like this one from Coin-Up

So I think the next job is to take back out the power supply board, rebuild the main capacitors and parts with the rebuild kit, and in a variable resistor to fine tune the +5V as per here:

I’ll document as I go although there is a fairly nice looking Williams Robotron power supply unit for sale in the US which are meant to be even more reliable, so I might just snaffle that one too… 🙂