I had on the bench this Aliens PCB:

Board had sever sprites issue:

I performed a MASK ROM check which reported two bad 4Mbit devices @K2 and @K8:

I was able to exactly reproduce the issue by using two dummy ROM files in MAME:

So, without further delay, I went to remove these devices and install two 40 pin sockets for the 27C400 EPROM replacements:

With these replacements fitted sprites were perfect but I noticed that sound samples (like voices of main character or enemies) were missing:

Sound samples are stored in a 2Mbit MASK ROM @D5 (which is not checked by the self-test) and its data are processed by a custom marked ‘007232’ which is a PCM controller:

Probing the 2Mbit MASK ROM revealed no activity on data and address bus, all pins were stuck high so I removed it:

and replaced it with a 27C400 (with doubled content since no 2Mbit MASK ROM replacement exists).This restored all sound samples.End of job.

I got this CAPCOM CPS1 A-BOARD (the old hardware revision) from my friend Joachim for a repair:

He said me that board had some input problems.This was confirmed once I powered it up since most of player 1 and 2 controls were irresponsive but, after few times I cycled power, suddenly the board lost the red color:

I started to troubleshoot first the input issue.As usual I inspected visuallly the board and found some corrosion near the JAMMA edge, some of the traces from the involved input pins to custom resistor/capacitor arrays and 74LS245 were eaten:

This was confimed also using my multimeter in continuity test.With some patching work and jumper wires I restored the connections and after this all controls were correctly working:

As for the red color issue, schematics for this hardware are available so I went to look at the involved circuit:

I found weak data signals on the two CXK5814 SRAMs (compatible with the TMM2018 suggested by schematics and PCB silkscreening) @4D and 5D (good on left, bad on right) :

Since the data bus is shared between these two chips I could not know which was exactly the bad chip affecting the other so I piggybacked both them and when I did it on the one @5D, the red color was restored.So I desoldered the chip and it failed the test in my programmer:

Fitted a new SRAM chip fixed the board completely.

Another board from my friend Marco and another quick fix.Got from him this original Kaneko Blood Warrior PCB:

On power up the board showed the “RAM CHECK OK” message but instead of going into game it was resetting in a endless loop:

Boardset is made of a CPU board and ROM board.Having a Great 1000 Mile Rally which runs on same hardware I could verify that the CPU board was good so the fault was located on the ROM board:

So, I wen to dump the program ROMs and compare them against MAME files.When I tried to read the one @U124 (a 27C010), my programmer reported a bad contact on PIN32 (VCC) and gave me an empty dump:

Device was internally damaged so I reprogrammed another one.Once fitted it, the board successfully booted into game without any further issues and I could declare also this board 100% fixed.