Friday, 17 March 2023

FM Towns Marty SCSI card reproduction

This is the follow-up to my latest post about my work on reproducing a couple of rare thirdy-part add-on cards for the Fuitsu FM Towns Marty console.The first made was the 2/4MB RAM expansion :

FM Towns Marty 2/4MB RAM expansion card reproduction

Also the SCSI card has been now succesfully reproduced :



This card allows to install games on hard disk and play doujin/homebrew software developed for this console released in 1993 by Fujitsu exclusively for the Japanese market.A big thank again to the user 'parodius' who loaned me the original cards.

Monday, 13 February 2023

FM Towns Marty 2/4MB RAM expansion card reproduction

Some months ago the user 'parodius' kindly loaned me a couple of ultra-rare add-on cards for the FM Towns Marty console, a video game console released in 1993 by Fujitsu, exclusively for the Japanese market.

They were a RAM expansion and a SCSI cards :

Since these cards are extrely hard to find (they popped up on Yahoo Japan Auction very few times) I took the chance to reproduce them.I started from the RAM expansion which is a nice add-on since it allows you to play on Marty some games that require more than 2MB of RAM.While reproducing it I stayed as close as possible to the original board layout, here is a side-by-side :

 Here's the reproduction plugged into the rear expansion port of the Marty console :

 Successfully tested it with Super Street Fighter II :

Thanks again to 'parodius' for the loan.

Thursday, 3 November 2022

C'mon and join 'Caius Arcade Repairs & Engineering' Discord Channel!

Recently I have created a Discord channel, you are invited to join as many as possible to chat about arcade repairs, technical aspects and other topics related to the wonderful world of arcade.Guests can send messages too in the chat box you can see on the right, no account required.So, c'mon and join now!

Thursday, 27 October 2022

Double Dragon (bootleg with 3xM6809) repair log

Some days ago I receved for repair this bootleg of Double Dragon.The PCB is made of a CPU board :


 and a VIDEO one :

It's a 1:1 copy of the original hardware with the exception of the HD63701YOP MCU which has been replaced by a 6809 CPU (bringing the number of these CPUs to three) plus a RAM, a ROM and a PLD.

I powered up the board and it booted up, game was playable with sound but sprites were affected by jailbars :

I repaired different of these boards so I knew this is a common failure which most of times is caused by a bad RAM on VIDEO board.Specifically there are two 2K x 8-bit static RAMs (2018 or 6116) that are part of the line buffer.I probed them with a scope and found some unhealthy signals on some data lines of the RAM @5M :

You can see on below picture a comparison between a good signal (on the left) and a bad one (on the right)

Sure enough I removed the suspicious RAM :

It indeed failed the out-of-circuit test :

I installed a good RAM on a machine-tooled socket :

This fixed the sprite issue and board completely.Another successful repair.

Saturday, 15 October 2022

Gang Wars repair log and 'ALPHA-8921/PRO-CT0' reproduction

Some time ago I've been sent a Gang Wars PCB for repair.For the uninitiated this game is a beat 'em up developed by Alpha Denshi and published by SNK in 1989.The board was in fair condition (a little bit dusty perhaps...) 

 At power up I was greeted by a static garbage screen :


Checking the program ROMs with a logic probe revealed stuck data lines :

At visual inspection I found that one the two SIL custom ICs marked 'ALPHA-INPUT87' was missing :


Time ago I made replacement of this part therefore I know that it's used for inputs and it's connected to 68000 main CPU data bus.I promptly installed the reproduction :

The board finlly booted but backgrounds had jailbars through :

Graphics data are stored onto four 4Mbit MASK ROMs :

Checking them with a logic probe revealed that pin 19 (data line D3) of the one @16J was stuck low :

 I traced the pin back to the SDIP64 custom IC marked 'ALPHA-8921' :

After a quick research on the net I found that the 'ALPHA-8921' can be found also on NEO-GEO hardware but under different part name, specifically as 'PRO-CT0' on AES cartridges and 'SNK-9201' on MVS boards.Regarding the functions of this chip, it can be used as graphics muxer on Alpha68k hardware and security device on NEO-GEO hardware.

The chip on my board was likely faulty so I removed it and installed a SDIP64 socket :

I borrowed a 'SNK-9201' from a Fatal Fury 2 MVS cart :

This fixed the graphics so this confirmed that my chip was really bad :


The repair was done but, since 'furrtek' during his NEO-geo development made schematics of this custom IC (thanks to him for his always brilliant job!) , I decided to design a modern replacement :

 The reproduction was succesfully tested on the Gang Wars PCB and Fatal Fury 2 MVS cart :

Sunday, 14 August 2022

Mitsubishi 'MA7054' reproduction

Recently me and my mate "Hammy" worked together on a custom chip reproduction project.The chip is marked 'MA7054' (manufactured by Mitsubishi as logo proves) and it's found on some Tecmo PCBs like World Cup '90 and Tehkan World Cup  :

The package is SIL, same of the 'MA7053' (reproduced as well),  another custom IC found on Tecmo PCBs but pin counting and spacing are different ('MA7054' is 15 pin 2.54mm whereas 'MA7053' is 28 pin 1.778mm).You can read more about the 'MA7053' here :

Mitsubishi 'MA7053' reproduction

'Hammy' traced the connections of the chip on an orginal board and studied its behaviour making comparison with some bootlegs we sourced.He ended up in an equivalent circuit which I routed to a proper board :

The testing of the reproduction on a Tecmo World Cup '90 was successful :


Thanks again to 'Hammy' for his invaluable help.


Sunday, 3 July 2022

Namco 'CUS27' reproduction

The 'CUS27' (or simply '27' as part marking says) is another custom IC found on Namco arcade PCBs of mid/late '80 like :

  • Pac-land, Dragon Buster, Sky Kid, Metro-Cross and other pre-System 86 hardware
  • System 86 hardware (Rolling Thunder, etc)
  • System1 hardware (Splatterhouse, Galaga88, Pac-Mania, etc) 

The custom IC comes in a plastic DIP42 package :

As for its functionality, the chip acts as a clock divider  :

The journey towards the reproduction of this custom IC actually started some years ago when John Bennett from UKvAc forums made some preliminary work, you can read more here :

Then we had a cooperation together, he made some progress so I designed a proper replacement which worked only on Rolling Thunder PCB :


After that time the project halted due to lack of time and motivation.This state perdured until some months ago when I found that the chip had been decapped so I contacted 'Furrtek' for some help.He traced the silicon die of the chip from picture identifying all the cells and then drawing schematics.In this way he figured out the full functionality of the chip, in particular he found that the chip can have different modes.At this point, after the hardest part was done, I came in and designed another replacement board :

The testing was successful on all PCBs I could try :


Thanks again to John Bennett for the initial work and 'Furrtek' for the completion, without them we would not have now a replacement of the Namco 'CUS27'.

Wednesday, 15 June 2022

Konami '005924' reproduction

 The '005924' is another custom IC from Konami used on arcade PCBs of the mid / late 80s like : 

  • Nemesis hardware
  • Twin 16 hardware
  • Contra
  • Jackal
  • Combat School 
  • WEC Le Mans 24

The chip comes in a ceramic SIL package (11 pin) covered by epoxy :


Technically speaking the '005924' is for main CPU reset generation, it acts as watchdog timer and handles coin counters, too.

Recently I have been asked me too look at this chip in order to made a replacement that would help people to fix their boards with faulty '005924'.

An arcade collector friend of mine sent me a chip which he had started decapping (thanks to him!)  :


I continued the work and exposed all the ceramic package drawing the schematics at same time.Then I routed a board layout :

Gerger files were sent to manufacturer and, after received the bare PCBs, I populated one with the needed parts :

The test on an Hard Puncher PCB (Twin 16 hardware) was successful, here's a video showing that all functions of original custom chip  (including the watchdog timer feature) were correctly implemented in the reproduction :

Wednesday, 25 May 2022

Taito 'PC010SA' reproduction

Another reproduction of a custom IC :  the Taito 'PC010SA'.The orginal part comes in SIL14 package :

It can be found on N.Y. Captor, The Legend of Kage, L.S.A. Squad, Tokio/Scramble Formation, Darius, Big Event Golf PCBs.

 'RCAVictorCo' decapped the part and drawn schematics of the internal structure (it's basically a  volume/tone/balance IC) so the step to design a replacement was easy and I did it :


 Here's testing on a Big Event Golf PCB :

Thanks again to 'RCAVictorCo' for his work.

Friday, 29 April 2022

'SNK I/O' reproduction

Recently I've been contacted by a couple of arcade collectors, both had a not working 'Prehistoric Isle in 1930' PCB (a  shooter game originally developed and published by SNK in 1989) with a problem regarding a custom IC marked 'SNK IO'.In one PCB the chip was faulty, in the other it was totally missing, likely removed to fix another board :

They asked me to take a look at this custom IC in order to study a replacement.Since I have a fully working Prehistoric Isle PCB I gladly accepted the challenge.

The chip come in a plastic DIP42 package, as said it's marked as 'SNK IO' (numeric string does not matter as I think it's a simple production/lot code that changes from time to time) but silkscreening says 'SNK I/O'.Besides Prehistoric Isle it's used on the 'The Next Space' (and perhaps other SNK boards, further info are welcome)   

As part name suggests, this custom IC handles the inputs, specifically the player 1 controls and dispwitches.As always I do, I looked for and found a couple of bootlegs so I studied how the functions of this custom IC were reversed.With the help of the user 'tekno retro' who did some check on his board I was able to figure out the full equivalent circuit of the 'SNK I/O' so I routed it to a proper board layout :

After some time I got the blank boards from the manufacturer and assembled one :

The testing was successful, the replacement worked flawlessly at first try :


Another custom IC reproduced, thanks again to 'tekno retro' for his help.

Sunday, 21 November 2021

'The Thing' - a FM Towns Marty FDD emulator - final revision

A quick update about "The Thing", the FM Towns Marty FDD emulator I made some time ago :

'The Thing' - a FM Towns Marty FDD emulator

The project recently has undergone a redesign and now it's mature for a release.I changed the layout of the main board and added a control sub-board.Now everything can lie inside the console :

Like the previous version, the emulator is powered by the open-source Flash Floppy firmware and it loads disk images from an USB storage (thumb drive or HDD).

'The Thing' can be installed normally on Marty consoles modded with DocBrown, the optical drive emulator designed by Deunan :

DocBrown ODE

But you can dislocate the control sub-board externally therefore you can use 'The Thing' on stock consoles, too.