Irem M92

 Encyclopedia  No Responses »
Apr 132024
 
Last Updated: 4/19/2024
Article Credit: ShootTheCore, wickerwaka, ekorz, System11, Apocalypse

Main Board

The Main Board is largely identical across all Irem M92 games. It is labeled either M92-A-A or M92-A-B.

GunForce A Board
Photo Credit: ShootTheCore
Hook A Board
Photo Credit: ShootTheCore

Early boards have less Object RAM (16K) installed at locations IC43 & IC44 than later boards (64K) – selectable by jumper J2 – but all M92 games are confirmed to function correctly with the 16K board. Thus, the difference in RAM was likely determined by parts cost at the time of manufacture.

16K Object RAM on Mystic Riders A Board
Photo Credit: ShootTheCore
64K Object RAM on Major Title 2 A Board
Photo Credit: ShootTheCore

Notable ICs

ICFunctionSilkscreen LabelLocation
NEC D71036L V33Main CPUH8
Nanao GA20Sound FX SamplesIC32 GA20B6
Nanao GA21SRAM DMA and Address Generation for GA22IC42 GA21M7
Nanao GA22Graphics RenderingIC63 GA22M10
YM2151FM Sound ChipIC33C6
YM3014Sound D/A ConverterIC208 YM3014C5

Secondary Board

The Secondary Board layout varies across the M92 games.

The Sound CPU resides on the secondary board and utilizes an encryption mechanism – see “Copy Protection” below.

GunForce B Board – Model M92-B-A
Photo Credit: ShootTheCore
Hook B Board w/Repair – Model M92-D-A
Photo Credit: ShootTheCore
Ninja Baseball Batman B Board – Model M92-Z-C
Photo Credit: Ebay
GameBoard ModelSound CPU ModelNotes
Blade Master / Cross BladesM92-B-A
M92-D-A
Dream Soccer 94
GunForceM92-B-A
GunForce II / GeoStorm
HookM92-D-A
In The Hunt / Kaitei DaisensouM92-E-B
Lethal Thunder / Thunder BlasterM92-C-B
Major Title 2 / The Irem Skins GameM92-B-FOnly M92 game to utilize an EPROM for saving scores.
Mystic Riders / Gun HokiM92-B-B
Ninja Baseball Bat Man / Yakyuu Kakutou League-ManM92-F-A
M92-Z-C
Perfect Soldiers / Superior Soldiers
R-Type LeoM92-C-N
Undercover CopsM92-E-B

Notable ICs

ICFunctionSilkscreen Label
Nanao 08J27261A1 V35Sound CPUIC10
Nanao GA23ROM Addressing (Assumed)IC23 08J27504A1

Board Variants

M92 boards manufactured for the Korean region have several noticeable differences from boards manufactured for other territories:

  • The green silkscreen is a lighter shade of green.
  • The JAMMA connector does not have a key notch.
  • SRAM ICs on M92 boards for other regions are manufactured by NEC whereas on the Korean boards they are manufactured by Hyundai and Goldstar.
  • The amplifier heatsink is physically smaller, and is colored silver rather than black.
  • One or both boards may be missing markings for the board type on the silkscreen.
  • A metal serial number tag is not present in the upper-right corner of the A Board.
Korean Ninja Baseball Bat Man A Board
Photo Credit: ShootTheCore
Korean Ninja Baseball Bat Man B Board
Photo Credit: ShootTheCore

There are also single-board bootlegs of several M92. They are much smaller than original M92 boards and thus are easily distinguished. Compared to the original games, bootlegs often omit animation frames, shorten the music tracks and gameplay slows down more frequently.

Ninja Baseball Batman Bootleg
Photo Credit: ShootTheCore

Common Issues and Quirks

  • The factory-installed capacitors are colored green or brown. The ELNA brand brown-colored capacitors are notorious for leaking and should be replaced ASAP.
  • Video output is darker than average with this hardware.

Protection Mechanisms

The Nanao 08J27261A1 V35 Sound CPU on the B Board enforces a security scheme where each game’s sound CPU code is encrypted in ROM and then decrypted by a key specific to the model of CPU. Thus, if the game ROMs are swapped to another game without decrypting the sound CPU code of the new game and re-encrypting the code to match the encryption scheme of the old game, the sound CPU will crash and the game won’t have sound.

Changing jumpers J1 and J6 adjacent to the Sound CPU from “S” to “N” disables the decryption mechanism and allows the CPU to run decrypted Sound CPU code directly.

Capacitor List (credit: System11)

Main Board

LocationCapacitanceVoltagePart No.
C2011 uF50 VECA-2EM010
C202470 uF25 VECA-1EM471
C203220 uF10 VECA-1AM221B
C20422 uF25 VECA-1EM220I
C209100 uF25 VECA-1EM101
C2101 uF50 VECA-2EM010
C21347 uF16 VECA-1CM470I
C2151 uF50 VECA-2EM010
C2161 uF50 VECA-2EM010
C2171 uF50 VECA-2EM010
C2181 uF50 VECA-2EM010
C2191 uF50 VECA-2EM010
C236100 uF25 VECA-1EM101

Resistor List (credit: fuzzbuddy)

  • R201 – 1KOhm
  • R203 – 100KOhm
  • R205 – 4.7KOhm
  • R208 – 4.7KOhm
  • R209 – 2.7KOhm
  • R211 – 10KOhm
  • R213 – 10KOhm

ROM Details (credit: MAME Source, ekorz)

LabelLocationEPROM Part No.Function
H0B Board27C020 (256kb)Main CPU
L0B Board27C020 (256kb)Main CPU
H1B Board27C020 (256kb)Main CPU
L1B Board27C020 (256kb)Main CPU
SH0B Board27C512 (64kb)Sound CPU
SL0B Board27C512 (64kb)Sound CPU
C0B Board27C040 (512kb)Background Tiles
C1B Board27C040 (512kb)Background Tiles
C2B Board27C040 (512kb)Background Tiles
C3B Board27C040 (512kb)Background Tiles
000B Board27C080 (1024kb)Sprites
010B Board27C080 (1024kb)Sprites
020B Board27C080 (1024kb)Sprites
030B Board27C080 (1024kb)Sprites
DAB Board27C040 (512kb)Audio Samples

Schematics (credit: wickerwaka)

Original Irem schematics are unavailable for M92.
wickerwaka developed a MiSTer FPGA core for the Irem M92 platform, and generated the following schematics (Source):

Additional Resources

MAME M92 Driver Source Codehttps://github.com/libretro/mame2016-libretro/blob/master/src/mame/drivers/m92.cpp
wickerwaka MiSTer FPGA Sourcehttps://github.com/wickerwaka/Arcade-IremM92_MiSTer/tree/main
System 11 Blog – Irem Games and Leaking CapacitorsWebsite is offline – PDF Archived on August 2017

Under New Management

 General  No Responses »
Apr 092024
 

Hi everyone – I’m pleased to announce that JAMMArcade will no longer be shutting down in August as previously posted.

I’ve worked with Porchy to transfer the site over to long-term, sustainable web hosting, and I will also be taking over the reigns as “editor-in-chief” of JAMMArcade going forward. Porchy will continue to host and manage the PLD Archive, and I strongly encourage all of you to visit that page and donate to support the hosting of that site – it’s a valuable resource!

Who am I? My online handle is ShootTheCore, and I’m a lifelong video game enthusiast who first learned how to diagnose and repair arcade boards by reading the logs here on JAMMArcade. I’ve been active in both arcade and console repairs for some time, and even started documenting my own repairs last year at https://www.shootthecore.tech . I’ll be migrating those repair logs over to this site gradually over the next few weeks.

In a nutshell, here is what to know about JAMMArcade.net going forward:

  • This website will continue to operate for the foreseeable future.
  • All of the prior content and downloadable files have carried over.
  • The login accounts that prior contributors used when writing for the site are still active.
  • If you’re interested in contributing fresh content to JAMMArcade.net, please contact me here.
  • If you find any broken links, please let me know.

Thank you for visiting JAMMArcade.net!

[4/9/2024 UPDATE – Site No Longer Closing]

 General  No Responses »
Apr 032024
 

After many years of arcade repairs, the time has finally come to hang up my soldering iron and move on. Its probably obvious that my interest in arcade repairs has dwindled over the last few years and with this site still taking up a lot of my space and file count, I think its time to close it down.
It will remain up until August which is when the hosting is paid up to. After this time the site will disappear so if there is anything on here that you want to keep, please make a copy of it before August.
The money saved from this will allow me to keep the PLD Archive Wiki up and running at a reasonable cost for a hobbyist.

Its been a great ride and I’ve loved most of my time in this hobby but the time has come to move on. Thank you to everyone that has ever supported me and this site and I wish you all the very best for the future.

Stay safe
Jon

 Posted by at 8:06 am

Crude Buster repair log #2

 PCB Repair Logs  1 Response »
Jul 082023
 

Hello,

This is my first repair log on an arcade board, i hope that my text will not be too long and useful to anyone having problems with their own PCB of the same game.

The preambule of this repair :

First thing first, i bought this PCB sold as broken with repair required, paid 130 euros.

On reception :

After pluging the board on my jamma system, i noticed that the board has at least 4 problems to fix.

The first is that i get japanese characters on screen. After reading each eproms and socketed maskroms, i see that FU-05 is from the wrong set. The solution was easy peasy : i bought a 27512 brand new on ebay, and burn the right content from the world set.

Once this first problem is fixed, i get this screen :

This error has already been solved by Porchy, this message appear when the routine that check the presence of the TC4 PAL chip fails. It indicates that the TC4 chip is wrong or toasted. And indeed, by checking with the magical finger touch, the chip is very hot.

So as a solution, i bought a replacement GAL 16V8 on ebay :

Now, the game boot correctly.

Let’s check the next problem to fix :

I see that the graphics are simply flashing constantly on the screen, it’s a mess. The culprit are the sram located here :

Those are TMM2063, and when i passed my finger on them, they were incredibly hot on touch, and the graphics were going crazy on screen. In order to confirm they are shot, i piggyback with new sram replacements bought on ebay : graphics are now fixed !

Let’s remove the buggers :

And install the brand new SRAMs :

Last problem to fix :

I noticed that jump button and start button for PL1 are not working. this board seems to have been connected backwards, so the RC1 custom components are shot. So i contacted Caius, who sold me 4 replacement RC1 pcbs, that i replaced on the board :

It was not easy to remove properly the dead RC1 components, i got 2 traces cut, that i patched after checking them with my multimeter.

Thanks to Caius on a few tips and hints here and there, the PCB is now fully working.

Another board saved ! 😀

Dlfrsilver

(With many thanks to Caius for the help and the replacement parts).

Duratool Desolder station repair log

 Equipment Repair Logs, Repair Logs  2 Responses »
Apr 142023
 

I’ve used this cheap desoldering station for many years now. Despite its quirks and constant demand for cleaning its been a great work horse.

The an immovable blockage happened recently and I just couldn’t clear it so decided it was time to replace the element. I thought I had a spare from years ago but turns out I have ordered the wrong part.
Looking for the correct part I found it was almost the same price to buy a new gun part itself and I wouldn’t have to mess around slicing the wired inside.

New gun came and all was well in the world for around 5 minutes when the unit got stuck in a reset loop.
Obviously there was a short somewhere so set to work checking resistance until I found a shorted element.
All the wires for this thing are very tightly routed and when i pulled them out I found this

Those small breaks in insulation from being sandwiched together so tight caused my issue. A little bit of insulation tape later and I was back in business

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