Since its intermittent, it is probably a connection issue - a ribbon cable likely, but could also be a lead of a PIA or something on the CPU board.

Could be something like when the game warms up, a connector warms up and completes a circuit, or the opposite, once it warms up, it loses connection.

That analogy could apply to the ribbon cable, either end of it, or anything along the way in the circuit.

The segment that is out in the pictures is segment 'g'

Look at page 63 of your manual, which is in the fold out schematic section, and trace segment g back through the display board to the CPU.

Note that you are looking for segment g - not segment g' - the ' means it's on display 3 and 4

It looks like segment g goes back through U12 to connector J1, which mates to the ribbon cable that runs to 1J22 (the ribbon cable) on the CPU. Specifically, 1J22 Pin #25. It also goes through SRC2 to pin 16 of U41, a 6821 PIA.

So, somewhere along the way, I would guess you have an intermittent connection. I'd start with the ribbon cable. Wiggle each end of it carefully with the game on, and see if the segment goes away and comes back as you wiggle it. If it's not that, then I'd carefully pull the display and check for cold solder joints along the path as listed in the schematic, as well as the CPU.

Nice write up John.

My taxi does this too. Upon turning on, the displays are usually scrambled for a few minutes. After the game is on for awhile, the display correct themselves.

Same thing happens with the music/sounds too. Warming up corrects things.

Strange. I should just pull the board and resolder the connectors for both.. I think the sound issue is something different though.

The displays and the sound board are controlled by PIAs on the CPU board. Perhaps there's something in common where one has a cold solder joint, or works fine once it warms up. Looks like U10 controls the sound, and U51 the displays. They have some components in common downstream.

Do you have a can of freeze spray? Fire the game up, and once everything warms up, hit the PIAs with a little freeze spray, and see if the problem returns... once you find what causes the problem to return, you know where the bad connection is.

How's your power supply output? In spec?

Hmmm... never tested the power supply. I should though, as the game reset the other day.

I generally just send boards out to Clive for repairs. This board set has never been out for repairs. Probably time.

Interesting idea about the freeze spray..

On my space station both two and four player are completely out. Does anyone have any suggestions on this I found in the manual there was one display fuse on the power board and it looked blown so I replaced it, but still no luck. Both are still not working.. Are there any other display fuses?

Thanks,
Cory

Did you switch the displays with working ones to see if it was the actual display first? Had one out on mine, I did this and realized the display itself was dead.