Darwin 4078 repair log

Received from Austria this rare original Darwin 4078 PCB (there are only bootlegs around)

Owner told me that he bought the board as working but then it failed after few minutes of gameplay.When I applied power to the board I could not get almost anything but a dimmed rolling picture that sometimes turned in the title screen :

 

All the video timing signals are generated on bottom board :

They are derived from a 12MHz crystal :

The master clock is divided and then inverted several times by a couple of 74LS04.Testing the one @12H (from Fujitsu...) with a logic comparator revealed bad outputs : 

The scope confirmed the unhealthy output signals (on right on the below picture, inputs on left) :

The IC failed the out-of-circuit testing :

Replacing the IC allowed the board to boot up but there were still some loss of video:

 Sometimes it showed only a fuzzy screen :

 I decided to test in circuit with a logic comparator all other Fujitsu TTL.I found a bad 74LS08 @10H :

 And a 74LS04 @10A with a floating output :

It obviously failed when tested out-of-circuit:

After replaced the ICs I tested again the board,it was fully working.Repair accomplished.