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Undercover Cops repair log #1

Aug 152015

Got two Undercover Cops PCBs (a native and a Alpha Renewal version converted one):

Both had sound issues.

The first one had all music but sound FXs were missing.In this kind of hardware (IREM M92) music is generated by YM2151 sound synthesis chip while audio samples from a “NANAO GA20” ASIC custom chip (QFP 80)

Probing the pins of the latter revealed no activity on its DATA/ADDRESS bus (it addresses and read data from the MASK ROM ‘W42’ on ROM board)

I dumped this device and it matched the MAME ROM set so problem could be elsewhere.Tracing back the connection from GA20 to the MASK ROM I found that some address lines were not in continuity like the other.I could pinpoint the break in interconnect ‘CN3’ which carryes signals from/to the two device:

A simple reflow was enough to restore the full sound.

The second board was totally silent, no audio at all.All the analog audio circuit was fine.I started to test ICs with my HP10529A logic comparator and when I put the clip on a 74LS74 @IC24 on CPU board, suddenly I got sound.So I inspected the solder side of this IC and found some evident dry joints , in particular pin 16 was not soldered on its pad, (probably I restored connection when I put the clip on it):

Also here a quick reflow was enough to fix the board.

Quick ROM ident program

General Comments Off

Aug 152015

I loved the old WinROMident program for its quick usage but unfortunately it hasnt been updated in a long time.
Ive made a new drag and drop program that uses Romcenter .DAT files

It doesn’t yet support zip files, only single files.
As with everything I make it requires .NET (v4.5) installed on your computer and it probably has a load of bugs too.
Its minimal and quick which is exactly what I need.

Can be found in the Downloads/Software section

64k expansion dump added & Rastan dumps tested

PAL Updates Comments Off

Aug 152015

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

Gun Smoke repair log

PCB Repair Logs, Repair Logs 2 Responses »

Aug 102015

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.

Rolling Thunder repair log #1

PCB Repair Logs, Repair Logs Comments Off

Aug 092015

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.

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