Metamorphic Force repair log

Got a Metamorphic Force PCB for repair :

The board was in very good overall shape but, when I powered it up, I got only a solid black screen,no video output.Checking with a logic probe the RGB colors revealed they were inactive :

The 68000 main CPU was running so I made some check with a video probe (a simple device that can display data on screen by using one of the RGB colors, in my case I used the GREEN one).I went to touch with the probe the GFX EPROMs and I got parts of graphics displayed on screen :

In this way I was able to figure that out the board was actually alive but playing 'blind' (with no sound, too).The final stage of the RGB colors generation is accomplished by some DACs in form of custom SILs marked '054573' (plus the '054574' that acts as filter/mixer).They converts into analog the digital signals of the '054338' custom ASIC (in QFP160 package) that receives, in turn, the digital bits from the three palette RAMs.

The outputs of the '054338' to the custom SILs were obviously inactive but also many of the inputs were in same state.Looking at Lethal Enforcers II schematics (which run on System GX hardware but shares same design) I figured out the '054338' receives some color bits from the '055555' custom (in QFP208 package) :

On schematics these signals are labeled 'PCOL' :

Probing them revealed they were all stuck so likely the chip was faulty.Having some spare I decided to replace it :

 The spare was soldered and area was cleaned from flux :

 

At power up I was finally greeted by the POST screen, the '055555' was really bad :

Board successfully booted, game was fully playable but, as previously said, the sound was missing at all :

Obviously my first suspicions fell on the '054986A' hybrid audio module which was in rough state :

I could have tried to replace the electrolytic capacitors on top but I settled things once and for all and opted to replace it with a reproduction of mine.The original module came off quite easily using hot air :

The reproduction was installed on a pair of header pin strips :

This gave sound back to this cool game.Board 100% fixed and another repair successfully accomplished.

'The Thing' - a FM Towns Marty FDD emulator

Some years I made some work on the Fujitsu FM Towns Marty, a home video game console released in 1993 by Fujitsu, exclusively for the Japanese market.Specifically I found the way to use a FDD emulator (HxC or Gotek) with this console, you can read my past article here :

Using the HxC Floppy Emulator with a Fujitsu FM Towns Marty

At same time I also designed a simple adapter to connect an HxC floppy emulator (or a real 3-MODE floppy drive) to the FM Towns Marty :

The adapter was really popular among enthusiasts (to the point that someone cloned it...) but it was not an immediate all-in-one solution.So, recently, I decided to design my own FDD emulator for the Marty console.I called it 'The Thing':

The emulator is based on the Gotek design and powered by the excellent FlashFloppy firmware so fully customizable and configurable (the settings can be specified in a configuration file called placed in the root folder or the USB drive).

Testing of the first prototype was successful, the emulator properly loads and format disk images :

Stay tuned for further update.

Irem 'KNA70H015(11)' and 'KNA70H016(12)' reproduction

Recently I have been working on reproducing the custom chips found on Irem M72/M82/M84 hardware.

Often these chips have scratched-off part number (especially in later hardware like M82/84) but on my R-Type PCB (M72) they were visible so I started my work with the 'KNA70H015(11)' (SDIP64) and 'KNA70H016(12)' (DIP48)

Functions of these chips are not really clear due to scarce info available, we have only the pinout from schematics so I studied them at 'low level" looking at previous hardware and trying to guess their functions.TTL thru-hole prototypes were done after some time :

Testing of both prototypes was successful on different boards :

 

This achievement opens obviously the way to implement the equivalent circuit on complex programmable logics for proper replacement of the original chip as well as making possible a multi board or a FPGA emulation.Stay tuned for further updates about reverse engineering of the other Irem custom chips.