Double Dragon (bootleg with 3xM6809) repair log

Some days ago I receved for repair this bootleg of Double Dragon.The PCB is made of a CPU board :

 

 and a VIDEO one :

It's a 1:1 copy of the original hardware with the exception of the HD63701YOP MCU which has been replaced by a 6809 CPU (bringing the number of these CPUs to three) plus a RAM, a ROM and a PLD.

I powered up the board and it booted up, game was playable with sound but sprites were affected by jailbars :

I repaired different of these boards so I knew this is a common failure which most of times is caused by a bad RAM on VIDEO board.Specifically there are two 2K x 8-bit static RAMs (2018 or 6116) that are part of the line buffer.I probed them with a scope and found some unhealthy signals on some data lines of the RAM @5M :

 

You can see on below picture a comparison between a good signal (on the left) and a bad one (on the right)

Sure enough I removed the suspicious RAM :

 

It indeed failed the out-of-circuit test :

 

I installed a good RAM on a machine-tooled socket :

This fixed the sprite issue and board completely.Another successful repair.