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side question for you guys -- this seems like a valid thread to ask this in...

I was just probing a board where the z80's address lines didn't seem to be flickering. Since I don't have one of those sweet audio probes yet, I was wondering if piggybacking another z80 would be a good way to see if the original is bad, or if that wouldn't work for some reason(s). What do you think?
 
Piggybacking a CPU is always problematic due high number of pins and due the fact it takes very little for crashing the whole system.Anyway, you can try.I had some success some times, I remember once I repaired a G.I. Joe with bad 68000, piggybacking a good one did boot into game.
 
The MAME dev who took care of the dumps asked me for better pictures of the GFX ROM board, he is not able to read the EPROM labels.I don't wanna to bother you so feel free also to not do it and tell me (and the MAME dev too) to go to hell :)
 
The MAME dev who took care of the dumps asked me for better pictures of the GFX ROM board, he is not able to read the EPROM labels.I don't wanna to bother you so feel free also to not do it and tell me (and the MAME dev too) to go to hell :)
:D

Some of them are indeed very faded. No way to read them from any photograph.

I'll examine them with my eyes and magnifying glass from different angles to figure out whats written. I'll take a note and upload an updated photo. I'll put the rom label markings on the photo ;)
 
Here is the picture of the ROM board. I examined the labels and written the marking on the picture for convenience ;)

Aliens_ROM_Board.jpg


And these are the check-sums of the ROMs. Notice the Gfx mask ROMs are indicated as if they are single big mask roms on the main board rather than individual small roms.

IMG_4433.jpg



IMG_4434.jpg
 
Fantastic job, many thanks.Yes, the test routine is the same of the single layer version so it treats the splitted ROMs as they were single ones.Thanks again, I will forward info to Dumping Union.
 
side question for you guys -- this seems like a valid thread to ask this in...

I was just probing a board where the z80's address lines didn't seem to be flickering. Since I don't have one of those sweet audio probes yet, I was wondering if piggybacking another z80 would be a good way to see if the original is bad, or if that wouldn't work for some reason(s). What do you think?
rather than piggybacking the Z80 check the reset and halt pins. it is more likely that a failed component which touches to those pins than a failed z80 ;)


Fantastic job, many thanks.Yes, the test routine is the same of the single layer version so it treats the splitted ROMs as they were single ones.Thanks again, I will forward info to Dumping Union.
I'm glad to contribute to MAME even with such small things which is nothing compared to what those guys are doing :)
 
This write up here just helped me fix my Aliens pcb today. Some static sounds present and humming but no actual sounds. A bad 74LS74 @ F9 was the cause.replaced it and sound came back.

Also had 4 bad mask roms. 3 came up as bad (J2, K2, J8) after replacing all 3 I still noticed some faint glitches in the characters and enemies. I removed K8 and reburned that as well. Now it is a fully functioning board.
 
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