Bogey Manor repair log

Got always from Austria for repair a rare Bogey Manor PCB.It's an oscure game released by Technos in 1985 :

As said, the board was faulty as graphics was totally scrambled, sometimes you could only see some sprites:

Although released by Technos actually the game runs on Data East hardware which has similarities with other 8 bit games from same manufacturer as MAME source suggests:

Data East 8 bit games

This hardware uses some custom ICs:

The ones marked 'HMC20' (DIP28 package) and 'TC15G032AY' (PGA135 package) seem to be involved in clock dividing and sprites generation while the 'VSC30' (DIP40) appeared to be related in some way to the tilemap/backgrounds.After some check I found nothing abnormal on the rest of the board hence I was quite sure one of these custom IC was faulty.Since the issue concerned the background graphics I focused on the 'VSC30' :

I found its pinout on the Express Raider schematics :

Probing the outputs revealed they were mostly stuck HIGH :

I piggybacked a good chip and got all the graphics back (although not correctly displayed due to not perfect piggybacking) 

This lead me to remove the part and replace it with a spare taken from a donor board :

In this way graphics were completely restored.At this point, as always I do, I launched the game under MAME and did some comparison to see if everything was correct.I immediately noticed some music tracks were missing on my board :

Here how it should be from a MAME recording :

Sound is generated by a couple of AY-3-8910 :

Swapping them with good ones revealed one was bad.Replacing it restored full sound and fixed board completely.The two culprits in the dock :

Another repair successfully completed.

P.S.

It seems this board, along with other ones from Data East of same era, the image is upside down from factory and no dipswitch is present to flip the screen.