Caius

Oct 072015
 

I thought this repair was the perfect opportunity to show you how to correctly servicing the ‘infamous’ Konami ‘054986A’ custom audio module (obviously this is valid also for the ‘054544’ one).Follow this guide at your own risk.I’m not responsible for any kind of damage!

Let’s start.

I got from my friend ‘supermik’ this Mystic Warriors PCB:

Mystic Warriors_PCB

Board played fine but had an orrible sound output, very loud and distorted:

Obviously the culprit was the ‘054986A’ module whose capacitors were replaced by thru-hole electrolityc ones:

054986A_recapped

But this was not enough to fix the issue.So, instead of troubleshooting the module (the 4558 OP-AMP and the AD1868R DAC undersneath were most likely bad), I opted for its complete replacement using a Premiere Soccer as donor board :

donor_board_054986A

The removal of a module consists in the following steps:

Prepare the board by covering the solderside with some aluminium foil leaving exposed only the pins of the module:

solderside_protection

Clamp an IC extractor on the sides of module:

IC_extractor

Put the board wrapped in a cloth or pillow  between your legs:

board_between_legs

Now, with an hot air rework station do a first preheating of a couple of minutes on the exposed solderside setting the temperature at 100 Celsius degrees.Then, set the station at 250 degrees for a minute or less:

preheating

In both cases, you have to move the hot air gun back and forth without stopping otherwise you could damage the board.

After done this preheating (needed to facilitate the solder melting and avoid heat stress) you have to use an heat gun for the last pass.Personally I use a 2000Watt model and set the temp to position ‘8’:

heat_gun

Keep moving the gun back and forth and at same time gently pull the IC extractor:

When the solder will arrive at the melting point, the module will come out easily from its seat:

removed_module

Next step is the sockets installation, use 1.78mm pitch ones (cutting a single socket in half):

sockets_installation

Lastly, mount your good module and you are set.

Ah, I forgot..board 100 fixed!

 Posted by at 10:45 pm

Flicky repair log #1

 PCB Repair Logs  Comments Off on Flicky repair log #1
Oct 062015
 

My friend ‘supermik’ sent me his Flicky PCB (released by Sega on System 8 hardware) for a repair:

Flicky_PCB

When I powered it up,I got this scenario:

bad_tiles

Sprites were fine but backgrounds were all wrong.Tiles data are stored in six 2764 EPROMs devices:

tiles_ROMs

When I removed them for dumping, I noticed a broken pin on one device which I promptly rebuilt:

pin_reworking

At same time I replaced four sockets of the tiles EPROMs (similar sockets are used also on Konami boards, they are beautiful but unreliable):

bad socktes

Backgrounds graphics were good now but still some glitches were present:

tiles_glitches

As I said, I dumped the six tiles EPROMs and they matched the MAME ROM set.But something still didn’t convince me so I used my video probe to check where the part of graphics affected was generated.For the uninitiated, the video probe is a small device that routes the green input from JAMMA to the video output allowing you to see on your monitor the signal captured with a probe.You can read more about here:

https://www.ukvac.com/forum/how-to-build-and-use-a-video-probe_topic328679.html

video_probe

So, in this way I could identify which EPROM generated the wrong graphics, it was the one @IC66:

Reprogramming a blank 2764 device with MAME ROM file fixed the board completely.

 

 Posted by at 11:32 pm

CPS1 PAL update

 PAL Updates  Comments Off on CPS1 PAL update
Oct 062015
 

Today I dumped and successfully tested the PAL marked ‘DM620’ @2A from a USA version of Ghouls’n Ghosts (CPS1 hardware) .Until now we had only the MAME dump which anyway matches this new one.The other PAL present on PCB is marked ‘LWIO’ and it’s already dumped since it can be found also on Final Fight board.

 Posted by at 10:18 pm

Ken-Go PAL dumps added

 PAL Updates  Comments Off on Ken-Go PAL dumps added
Oct 062015
 

Yesterday I dumped the four PALs from a Ken-Go PCB (an undumped revision on Irem M84 hardware, it will be included in the next MAME release).They differ to the ones already on database except for the one @IC5 which is the same.Dumps have been successfully tested on GAL16V8 targeting devices.

 Posted by at 9:18 am

Raiga – Strato Fighter repair log

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Sep 302015
 

I got on the bench this Raiga – Strato Fighter PCB for a repair:

Raiga - Strato Fighter_PCB

Game is a horizontal side-scrolling space shooter developed by Tecmo in 1991.Two were the issues I got when I powered it up.Sound was completely missing ( I got only some samples played randomly) and there were missing vertical lines all over the screen like a sort of scanlines effect:

missing_vertical_lines

All video related circuitry is located on he bottom board.Since involved EPROMs and RAMs were socketed I could test them out-of-circuit and they were fine.Then I noticed some dynamic RAMs in form of 12 Sharp LH2464 (64K*4bit) chips.I went to probe them with my oscilloscope and I found weak signals on two data lines of a couple of them (good signal on left, bad on right of the below picture):

data_lines_comparing

So, I removed the two chip and tested into my EPROM programmer where they both failed:

LH2464_failed

With two good DRAMs fitted, the graphics were completely restored:

GFX_restored

So I went to troubleshoot the lack of sound.Main CPU of the audio digital section is a Z80 which commands two YM2203 FM sound synthesis chips for the music and one OKI 6295 for the voice samples.Probing the Z80 revealed random activity/pulsing on all its pins.Besides, chip was wery hot to the touch so I decided to replace it.This was the right move.Board 100% fixed.

 

 Posted by at 10:59 pm