Today I added a PAL dump from a 64k memory expansion module for the Amstrad CPC. I dumped this a long time ago but it never got added so I cannot really recall the details. I *think* it was a Datel device.
Yves M has converted the tw PAL dumps for Rastan that were in PAL16L8 format into GAL16V8 format and tested them successfully on his PCB.
Thanks to him
Another board from my friend Alexander.It’s time for an original Gun. Smoke PCB:
Board booted fine but had a graphical fault where backgrounds were totally wrong (MAME screenshot on the right) :
In absence of schematics, MAME source is always a great help.Looking at it I was able to identify the ROM cointaining the backgrounds data:
ROM_REGION( 0x8000, “gfx4”, 0 ) /* background tilemaps */
ROM_LOAD( “gs14.11c”, 0x00000, 0x8000, CRC(0af4f7eb) SHA1(24a98fdeedeeaf1035b4af52d5a8dd5e47a5e62d) )
I dumped it and it matched the one in the MAME ROM set.So, problem had to lie in the external circuitry.Tracing back connection from this ROM I figured out the its address lines were connected to outputs of some 74LS283 whose inputs were tied to some 74LS273.So, I started to test them in-circuit using my HP10529A and BK Precision 560A.All was fine until my equipment reported a problem on the 74LS273 @8D:
Piggybacking this cleared the issue:
IC failed when tested out of circuit reporting trouble on PIN2:
Fitted a new IC fixed the board completely.
Got this original Namco Rolling Thunder from my friend Alexander for a repair :
Board didn’t boot up but got stuck on this screen which repeated itself in a endless loop sign that the watchdog circuit was active :
My friend Alexander gave me an hint to troubleshoot this fault pointing me to a bad custom ‘130’
As I swapped in a know good one from a board of mine, game successfully booted but showed a strange graphical fault where the main character didn’t disappear when entering in a door:
As usually I started my troubleshooting with a visual inspection and found a deep scratch on the solder side and after checking with a multimeter I could notice that involved trace was severed:
After consulting the schematics I was sure that the broken trace was indeed in the sprites circuitry :
Restored the trace cleared the sprite issue.Job done.
Today I dumped one PAL from a Major Title 2 PCB (M92 hardware) which has been converted into Undercover Cops.PALs on CPU board (M92-A-B) are the same for all M92 games but the ones on ROM board are specific by game with some exceptions though.In particular this Major Title 2 ROM board (M92-B-F) has two PAL16L8.The one labeled ‘MT2_B-2L-‘ can be found also on Gunforce (and maybe others) under different label but same equations, the other one ‘M72-B-7H.D’ was undumped until now.Dump has been tested as working in a GAL16V8 targeting device.
Some days ago Dragos sent us some pictures of his Konami hybrid sound modules reworking.As most of you already know, this customs are used in many Konami arcade games.Specifically the ‘054986A’ is used on Lethal Enforcers, G.I. Joe, Metamorphic Force, Run & Gun, Premiere Soccer, Bucky O’ Hare, Violent Storm, Monster Maulers, Martial Champion, Mystic Warriors, Gaiapolis and Wild West C.O.W. Boys of Moo Mesa while the ‘054544’ is present on X-men and Xexex.A common fault on these customs concerns the SMT electrolytic capacitors that after some time start to leak ‘eating’ traces of the module.What Dragos did was to literally ‘undress’ the modules by removing the black paint using this paint stripper (that you can find in your country under a different name) revealing in this way all the traces and connections on top and bottom layer.Needless to say that this is really useful for everyone who wants to troubleshoot the modules.But, here are the pictures for a better understanding.Let’s start with the ‘054544’:
A nice black repaint is what it takes after a recap…
Here is below the ‘054986A’ in all its glory:
Above, a close up of jumper wires needed to patch some broken connections
In the picture above you can see the ‘054986A’ top layer exposed.The small IC on the bottom left between the two 10uF 16V capacitors is a 78L05 voltage regulator (SOT-89 package) which powers the 4558 OP-AMP and the AD1868 DAC on the underneath of the module
Now Konami hybrid sound modules have no more secrets!Thanks again to Dragos.