Got from Portugal five faulty G.I. Joe PCBs to repair (hopefully all of them…).I had a good start and could fix two of them.

The first board was in good shape with no missing parts:

It booted into game but colors were completely wrong and most of graphics missing:

I launched a MASK ROMs check which reported all the devices as good so the problem was elsewhere :

I remembered I had a similar issue in some of my past repairs, the culprit was the ‘053251’ custom ASIC which is present on my board too:

The Simpsons repair log #3

This custom takes on input different layers of graphics as well as some priority bits and outputs 11 bit of palette index plus two shadow bits (info taken from MAME source)

I went to replace the IC with no further analysis:

Graphics were completely restored and board perfectly working with no other issue :

The second board was in good shape and complete too :

But it booted to a static pink screen :

Also in this case my suspicions fell on the ‘053251’ custom ASIC :

I replaced it, it was really faulty.Now the board tried to boot but failed the power on self-test:

The bad reported devices were all part of the sound circuit : @7C (SOUND ROM), 6C (SOUND RAM), @3E (‘054539’), @2D (62256 SRAM)

The sound CPU is a Z80B, probing it revealed floating address/data lines:

Luckily the CPU was aready socketed so I swapped in a good known one (a Z80E with clock up to 8MHz)

The board got now past of the self-test and booted into game but sound was absent:

Obvioulsy the culprit was always him, the ‘infamous’ ‘054986A’ hybrid module:

As I usally do, I removed it :

and installed proper sockets:

Then I serviced the audio module replacing the OP-AMP underneath :

and electroytic capacitors on top:

Sound was fully restored and double repair accomplished.

Received today from Germany this Guardians PCB, also known as Denjinmakai II, a horizontally-scrolling beat-em-up released by Banpresto in 1995)

According to the owner the game played totally ‘bind’.I could confirm it as soon as I powered the board up :

But, as you can see from above video, I was able to restore some graphics by pressing down this surface mounted custom ASIC (QFP 208 pins)

Judging from the heatsink on its top this custom ASIC acts as a GPU generating most of the graphics and video signals too.At a closer inspection I found many lifted pins on all four sides.An example :

I promptly reflowed the IC, this gave me a steady picture but all the graphics were scrambled and, judging from the blueish screen, the RED color was missing too :

Looking at solder side of the PCB I noticed a long and quite deep scratch passing across some traces:

Inspecting the area with a microscope and doing a continuity check with my multimeter confirmed that some traces were severed and other caused unstable contact:

I patched and reinforced the traces with some AWG30 wire :

This lead to few improvements, graphics were still scrambled so I moved on to troubleshoot the lack of RED color.This was pretty easy to fix as the board had a quite clear damage that broke the trace which carries the signal to JAMMA edge connector :

As for bad graphics, I decided to double-check the previously reflowed custom ASIC and found a solder bridge shorting two pins:

Removing it fixed the issue and board completely.Repair accomplished.

Got from Portugal this Out Zone PCB, actually a low-budget korean version :

At visual inspection the board lacked of two 6116 SRAMs (but sockets were installed)

After fitting them I powered the board up and I got the usual black/white wavy striped screen but no boot into game, 68000 main CPU got stalled right after :

Multiple could be the reasons, in particular this Toplan hardware requires the sound circuit to be running otherwise the whole system can’t be initialized.A Z80A rules the sound system :

When I did piggybacking on it I got a ‘SUB CPU ERROR’ message on screen :

Once removed the IC I had confirm that it was really bad.With a good Z80 the board successfully booted into game but sprites were all blocky (it seems this is a common issue of this hardware…)

Sprites data are stored in four 1Mbit 28 pin MASK ROMs :

Devices were soldered in on my board and not socketed like usual so I was forced to remove all of them for dumping.Two of them gave different CRCs at each reading :

Specifically the ones marked ‘ROM1’ @1B and ‘ROM4’ @1L :

I replaced them with two 32 pin 1Mbit non-JEDEC EPROM devices.All seemed fine but while playing the game I noticed some sprites (like explosions) had lines through :

Looking at hardware I figured out that the sprite line buffer is made of four 6116 (2k x 8-bit) static RAMs:

 Probing them with a scope revealed some dead outputs of the one @12L :

The chip failed the out-of-circuit testing:

Installing a good RAM chip finished the job.Repair accomplished.