Edward Randy repair log

I got an Edward Randy with a black screen (but partial sound).

After a few checks with my scope, I quickly found a PAL @ location N5 with no signals on all of its outputs (BUT signals on its inputs).

As PALs from this game are not available yet online, I looked for other games that possibly shared the same hardware/system in order to try using a similar PAL.

And yes, that system is listed as “Data East Caveman Ninja Hardware” in MAME and some of these games got their PALs dumped. It was the case of Caveman Ninja and Robocop 2 that shares an almost identical PCB layout than Edward Randy (there are only a few differences in the GFX ROMs part).

So I burned the PAL at location N5 from Robocop 2 and plugged it on my Ed Randy board and here is what I got:

Well, at that time I was thinking it was due to an incompatibility between Robocop 2 and Edward Randy PALs and I temporarily gave up, waiting to get a dump from a working Edward Randy to be sure…

Then Shoestring confirmed me Caveman Ninja and Robocop 2 PALs @ N5 were strictly identical. It leaded him to believe that perhaps they are all common to each other and maybe there is a different problem with my board, which pushed me to have a look back at my board for possible other faulty chips. And he did well…

I started looking for other issues on the PCB and noticed that bending the board made the garbled graphics changing, even making them better looking at some point.
So I suspected the two SMC Data East customs labeled “55” having bad solder joints and reflowed the solder on them.

It then went way better. I had clean backgrounds in game, full intro with clean texts and pictures, title and Data East logo appearing (didn’t have all of that before) but no sprites in game. I noticed a square on the bottom-right corner that seemed containing garbled parts of sprites.

I then managed to find where the sprites part was located on the board and found two 6116 RAMs @ locations N9 and M9 that had suspicious signals on their data lines (pulsing but weakly and at low voltage). Piggybacking a known good working compatible RAM made parts of garbled sprites randomly appearing on screen.

I then desoldered one of the two RAMs (at location N9). With no big surprise it was tested bad on my programmer. I soldered a socket and put a new RAM in place. There was still no sprites but the garbled square on the bottom-right corner was not there anymore. Data lines on the new RAM were looking pretty much better though with strong pulses at 5V. The RAM located at M9 still showed weak outputs so I replaced it with another good known RAM:

Then sprites magically appeared !

Only one thing was remaining: the voice generating chips (2x OKI M6295) were missing so I replaced them and got the sound fully working.

I played the game several times since that and it is working perfectly.