Monday 2 October 2023

'ZILOG' - a MSX2+/turbo R FDD emulator

'ZILOG' is an internal floppy disk drive emulator I designed for the MSX2+ and turbo R computers ( equipped with built-in FDD).You can read more details about these machines here :


MSX turbo R

Like for 'The Thing' (the FM Towns Marty FDD emulator), 'ZILOG' (which I named like this in honor of the Z80 CPU that equips these home computers) replaces the internal mechanical floppy drive with a board able to emulate the floppy interface reading disk images stored on a USB flash drive :

'ZILOG' emulator is powered by the great Flash Floppy firmware and can be controlled by a small external rotary/OLED board :

Testing of the emulator on my MSX2+ Panasonic FS-A1WSX :

Thursday 21 September 2023

Mitsubishi 'MN50005XTA' and 'M60002-0118P' reproduction

The Mitsubishi 'MN50005XTA' and 'M60002-0118P' are two custom chips found on Tecmo arcade PCBs of mid/late '80 like Rygar/Argos no Senshi, Silk Worm, Gemini Wing, Solomon's Key and few other boards.

The Mitsubishi 'MN50005XTA' is a DIP28 .600mil plastic part :

Whereas the 'M60002-0118P' is DIP42 .600mil (always with plastic case)

I had these two custom ICs in my reproduction TO-DO list since some time, it was only matter to find some bootleg boards to study how the function of these custom ICs were reverse-engineered.

As soon as I found them I extracted the equivalent circuit and then designed the replacements with simple TTL gates :

'MN50005XTA' reproduction :

'M60002-0118P' reproduction :

Both replacements worked at first try when tested on my boards (Rygar and Silk Worm)




Since the designs have been validated a CPLD version of the TTL reproductions will follow later.

Sunday 10 September 2023

Altered Beast repair log

Got for repair an original Altered Beast PCB (on Sega System 16B hardware)

Board was in decent condition :

 It was marked with 'GFX issue" and, indeed, at first power up I could see it :

There were missing horizontal lines all over the screen.The fault(s) was located on motherboard since the ROM board was successfully tested with a known good motherboard.

At first glance this issue appeared to be related to backgrounds graphics, indeed someone previously replaced in vain the '315-5197' PGA custom tiles generator and a couple of RAMs connected to it.

I ran a memory test which reported all RAMs as good.But on motherboard there are other memory chips not addressed by main CPU therefore these are not covered by the test, in particular these RAMs are tied to the '315-5196' PGA custom sprites generator.Here is a RAMs chart for reference :

The sprite RAMs ICs were all Sony CXK5814 (2K x 8-bit), I know from my experience that these are quite prone to failure.I started to probe the two @G2 and G3, the signals on most of data pins looked like unhealthy compared to a good one (on the right of picture below)

I pulled both chips :

Actually only the one @G2 failed the out-of-circuit test (the other was good)

I installed a good RAM chip on socket :

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

Monday 4 September 2023

Irem 'KNA65005-17' reproduction

Another Irem custom IC has been defeated and successfully reproduced.

After the 'KNA70H015(11)' and 'KNA70H016(12)'  

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

I took into account the 'KNA65005-17', a DIP48 part found on M72 and later hardware like M81, M82, M84 and M85 (although with scratched-off part name)

The functions of this custom IC were reversed by analyzing and comparing the signals between original and bootleg hardware.As always I ended up with a prototype made with TTLs gates:

After some tweaking, it worked fine on all PCBs I could try.

Here's testing on R-Type (M72 hardware) and Dragon Breed (M82 conversion) 


Since the design has been validated a CPLD version of this TTL reproduction will follow later.And a full re-engineering of the entire Irem PCB is more possible now.

Friday 18 August 2023

Renegade repair log

 Bought some time ago from US an original Renegade PCB :

I was after this board since years because I like the game, a beat'em up developed by Technōs Japan and published in 1986 by Taito.You can read more about this game here :

Renegade : an immediate predecessor to Double Dragon

The board was marked as faulty with a sprite issue like stated on the sheet that was inside the package :

But, actually, when I first powered board up I was greeted by a static garbage screen :

I reseated the ribbon cables and gave a clean to the pins of the connectors, the board finally booted up and I could see sprite issue that affected some of the enemies :

The sprites data are stored in twelve 27256 EPROMs located on bottom video board :

I dumped them and noticed that my programmer gave a different checksum on each reading of the device labeled 'ND-5' @IC79 :

This is the clear symptom that the EPROM is faulty.Indeed, any of the dumps of this device was not recognized by MAME :


Out of curiosity, I tried one of the bad dumps in MAME and got exactly the same issue of the PCB :

I programmed a good 27256 EPROM with MAME ROM file, this fixed the sprite issue :


No other issue found therefore board 100% working and another classic added to my collection.

Thursday 3 August 2023

Seta 'X1-007' reproduction

Recently 'Furrtek' decapped the Seta 'X1-007' custom chip donated by me (this part, in SDIP42 package, is used on many Taito/Seta PCBs as RGB latch and video SYNC generator)

I took the chance to put his (always) brilliant work into practice and made a replacement of this custom IC using a +5V CPLD to embed all the logics that 'furrtek' extracted from the silicon die :

Testing of the reproduction on Insector X PCB was successful :

A huge thanks again to 'Furrtek' for his invaluable work.

Tuesday 25 April 2023

Data East double repair log (Bogey Manor & Last Mission) and 'RCDM-I4/RCDM-I5' reproduction

Some months ago I finally found a Bogey Manor PCB,I was after this board since ages.For the uninitiated Bogey Manor is an obscure game released from Technos in 1985 (but actualy running on Data East hardware), you can read more about here :

Bogey Manor review

The board was in quite good condition ( a little dusty though...) but marked as faulty

Indeed, at first power up, it was completely dead, no sign of life.As always I do, I did a visual inspection of the board and found that the black SIL component marked 'RCDM-I4' was loose, almost detached from the board :

After a quck check on schematics of similar Data East hardware I realized that this part is responsible of main CPU RESET generation :

I managed to resolder the component to the PCB and board sprang to life :

Game was fully playable but sound was missing, I promptly pinpointed the fault to a missing amplifier (Fujitsu MB3730) in the sound section :

 I installed the amplifier :

This restored sound and fixed the board completely (screen upside is not an issue but a behaviour of the board as there is no dipswitch to flip it)

Happy of the result I decided to take a look at another board from Data East from my pile of faulty boards : Last Mission, a top-down multidirectional shooter released for the arcades in 1986.

The board was in fair condition :

It booted up but background graphics were bad and sound FXs were missing, too :


From a quick check I figured out that the circuit that handles this part of graphics is located on top board so, for first, I dumped the ROMs and they were good.My attention was caught by the presence of some Fujitsu TTLs :


Well all know they are very prone to failure and fail always in the same way with floating or stuck outputs.I went to probe them and, indeed, found the one @12B with a stuck output :

This was also confirmed by a scope (input signal on left, bad output on right of below picture) 

 The IC failed when tested out of circuit :

Replacing the IC restored the graphics completely:

The lack of soud FXs was pretty easy to troubleshoot.The sound effects are generated by a Yamaha YM2203 sound chip (while a YM3526 handle the music)  and then routed to the serial data input of the YM3014 DAC :

Checking this input with a scope revealed few activity :

So, sure enough, I pulled the YM2203, installed a rounded socket and a good IC:

This restored full sound and fixed board completely.Before archiving this yet another repair I noticed that Last Mission PCB used a similar black SIL component to the 'RCDM-I4' used on Bogey Manor, this was marked 'RCDM-I5' :

Looking at schematics, this part has same pinout of the 'RCDM-I4' but it's used for coin input hadling :


Anyway, I tried to swap the parts and they resulted perfectly interchangeable.Therefore, having a broken part, I thought it was nice to decap ad analyze this in order to have a replacement.The part was not really complicated inside so a reproduction was pretty easy and quick to do :


Testing was successful on the freshly repaired Last Mission PCB :

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.