I bought this faulty Point Blank PCB for cheap on Ebay:

Seller said it had graphical corruption and was missing a primary color and sound.When I powered it up I actually had sound but the other two issues were there:

The missing color was the green, tracing the pin 12 solderside back from JAMMA connector I found the culprit : one of the three SMD transistor ( each of which drives a color output) was missing:

Green was so restored :

but graphical troubles were still there.Inspecting the board I found that some pins of the custom C355 were smashed:

This custom handles the motion objects (sprites) and my issue concerned this part of graphics.Having a spare Namco NB-1 board I opted for a replacement of this ASIC :

 

After some work and pads rebuilding, I ended up with this result:

In this way graphics were completely restored but sprites had jailbairs:

Pressing down the board fixed the issue temporarily, inspecting again the board revealed a liften pin on a TC51832 (62256 compatible)RAM @12R:

Resoldered the pin and board 100% fixed.

I had a spare Sega System16B ROM board type ‘171-5797’.Originally it mounted the E-Swat ROM set but I decided to convert to Golden Axe since I missed this game in my collection :

Atter burning the Golden Axe MAME rom set, I powered the board up and game was fully playable but with a noticeable sprites issue:

Judging from fault, I immediately thought about an addressing trouble of the sprite EPROMs (27C020 devices) so I went to check for continuity of their address lines.They were properly daisy-chained each other but the pin 30 (A17) of all of them was not connected to any pin of the ‘CN2’ interconnect (signal to address lines come from motherboard) :

Lack of signal on this A17 address line was confirmed also by my analog scope (good signal on left, bad on right of the picture below):

So, the trace had to be broken under the ‘CN2’ interconnect.Being not available schematics and wanting to avoid to desolder the whole connector, I soldered the end of a wire to PIN 30 of a sprite EPROM and with the other end I touched each pin of the ‘CN2’ interconnect that gave me no continuity until I hit the right one restoring correct sprites:

Lastly, I made the fix permament holding the wire with some hot glue:

That’s all for today.

I had this rare Irem Ken-Go PCB (an undumped version included in latest MAME release) from my friend Joachim for a repair:

The board played fine except for an issue where all sprites were formed but missing all colors appearing like black shape:

Sprites generation circuit is located on top board where some customs lie:

Documentation for this specific game was not available but luckily I could know function of the various customs by looking at the R-Type schematics and so identity the one involved in the sprites palette generation:

The custom itself was marked ‘KNA91H014’ in 60 pins QFP package:

Probing it revelead that inputs were fine but outputs had irregular signals:

So I opted for replacing this custom (taking a good one from a dead Vigilante board)  :

This was the right move since sprites were correcly restored:

End of job.