Back after a decade - Williams Joust Video Problems

[daeven]

I've been gone from here for a long time!  I just moved and decided it was time to revisit my arcade game hobby after moving the heavy cabinets around.  I think I had a HDD failure on my MAME system, but I'm most interested in getting my original Williams Joust game working again.  Last time around, I believe I did repair on the power supply and initial troubleshooting lead me down the path of needing new DRAM chips.  I opted for ordering a multi-Williams board, but never installed it. 

The game was just displaying a static rug pattern.  Standard troubleshooting is to look for the numeric code on on of the boards, but first I changed the batteries, inspected everything, unplugged and reconnected all ribbon cables.  Now the game boots completely and plays, but the video has a doubled pattern.  I struck out with Google searching looking for similar issues.

A picture of the screen is attached.  Does anyone have any ideas or pointers one where more of the Williams games troubleshooting details are located?

[bperkins01]

Double screen like that is an issue with the board I would guess  w/o looking at the schematic.. I would think in the vsync counters.  I had a very similar issue with a Centipede board I repaired.  A logic probe checking the vsync counter chips is where I would start.  Does it play double too?  and the guys scroll off of one part and into another like they are stepping through folds in the screen? 
Based on just that pic.. I'd be looking in that area of the board.

[daeven]

Everything is normal left to right.  The game seems to play just fine.

I got some feedback from an Arcade Repair group on Facebook.  It seems the chips referred to as "Special Chips" are likely to blame.  I popped them off and reinstalled and it didn't help.  Everything in there looks very clean, but I'll try cleaning it up before looking for replacements.

[bperkins01]

I don't know the Joust boards all that well - there is a vertical decoder rom.. (3C)
I'd look there.  It appears the vertical sync comes off of that chip?

Even a logic probe on it pins 1-8 may show a stuck signal.  They should all be toggling.
Press on the chip to see if the screen moves or see if its hot to the touch..  It would give you some info...
Although - It says its a ROM - not sure if its part of the ROM check since its not on the ROM board...