Another CPS1 on the bench, it’s a very unreliable hardware and it is prone to several failures over the ages. It come from the personal collection of Sasha a friend of mine, the board seems to play in the right way few days ago, but once on the test bench for a quick checkup with my surprise it perform a solid black screen.

The usual suspect in this case is the battery, a CR2032 button type, that keeps the decryption table alive on the “C” board. I picked up the multimeter and promptly tested it:

.. 0.8 volts are not enough to power up the RAM inside the CPS-B-21 custom chip on the underside of the small “C” board, so it must be replaced or removed at all. This is a clear sign that the board has been committed “suicide”.

To confirm my suspect and to be sure this is the only issue that prevent the game from running i swapped the encrypted program eproms with the proper decrypted and flashed ones and swapped the Three Wonders “C” board too with a ready-to-go one taken from a Pang3 on my personal collection. This must be done because as we can see later in this post its original “C” board needs an hardware modifcation to be able to run decrypted program code. Here we go …

Once feeded the power to the board i was greeted with the usual CPS1 startup RAM tests and then the game:

This is a good sign that the board is almost working in the right way, but sometimes the audio samples and FM music were wrong or they were missed at all. Power cycling the game bring the audio back, but after few seconds it goes away again. I’ll take care of it in the next post, because the culprit should be spotted on the main CPU board, now we must take care of our “suicide” battery.

So we can proceed by reprogramming the 4 EPROMs containing the encrypted program code, they are seated on 30, 31, 35 and 36 sockets on the “B” CPS1 game board. I gently and carefully removed the labels:

Once the UV EPROM windows have been exposed they can be cleared with an erasing cycle on my EPROM eraser:

The process will take about 20 minutes, so in the meanwhile we can take care of our “C” board and make the hardware modification required to let the CPU running the proper program code. You can find all the useful information about CPS1 de-suicide procedure in this site:

The Dead Battery Society.

Here is the suggested procedure taken from the above site:

“To fix your game, download one of the patched sets below and take a look at the file names. Find the EPROMs on your board that correspond to the file names and burn the new data onto an EPROM that is the same size as the original. Remove the original EPROM(s) and put the freshly programmed EPROM in thier place. Now you’ll need to make some modifications to your c-board. First remove the battery. Next, locate pins 45 and 46 on the CPS-B-21 chip. You’ll notice there are tiny traces connecting these two pins to ground. Carefully cut these traces with an exact-o knife or whatever works. Don’t cut the nearby traces. After cutting, it would be a good idea to measure resistance from ground to these pins with a volt meter’s ohms setting. If there’s still a connection, you’ll get a reading of near zero ohms resistance to ground. However, once severed, the pins still won’t read open because of the CPS-B chip’s internal connections. You should read a few mega-ohms of resistance to ground. If you are working on 3 Wonders, or a similar c-board, you may think there are no traces connected to pins 45 and 46 to cut. They are still there, they are just connected to the pins from under the chip where you can’t see them. You will have to snip the bottoms off those pins, leaving enough to solder to. Do not connect +5v to these pins until you are sure they’re no longer connected to ground or you will be making a very short path from +5v to ground and smoke and fire will be sure to follow if you apply power. Once these pins are cut, add a blob of solder to the two pins and run a wire to a nearby source of +5v to pull them high. Here’s a picture. If your game works but the graphics drop out and disappear at certain points, you might want to test pin 40 to make sure it’s also being pulled high. This is the pin that formerly was supplied power by the suicide battery. It should normally be pulled high when the game is on, but you may have a bad diode or something causing it to not get pulled high.”

I removed the battery:

… and than i made the required modifications to the board, i secured the patching wire with some hot glue too:

Once the EPROMs are cleared and tested blank they have been programmed with the decrypted code, original labels were applied in place, and than i re-seated the ERPOMs on their sockets.

The modified original “C” board has been plugged in and now we must proceed with the smoke test … finger crossed as usually:

… and the board il playing fine, but now the audio is totally missed. I swapped for a known good “A” main CPU board, and with this board the audio is playing flawlessly so the “B” and “C” boards are fully working .. good news for my friend Sasha.

STAGE 1 CLEAR … stay tuned for the next “audio fixing” stage …

Get ready for next stage!

Troubleshooting issues on CPS1 A board is sometimes quite difficult because the stacked ROM board covers the CPU board, prevent accessing the chips, especially with the “short” board which is populated by SMD (surface mount) ICs.

By the way you can use special cable extensions with 64 pins IDC connectors, so you can put aside the B and C boards.

In this way the chips are exposed so you can use against them your favourite tools 🙂

Here is a close-up of the audio section of the board:

I started checking control signals on the Z80 audio CPU, pinning the probe on the clock line on pin 6 reveals a totally silent line, an healty cpu clock should be a sqare wave with rising and falling edges for each clock period like this:

this can be due by a very bad cpu, a broken trace or a bad crystal clock oscillator. It’s very rare to find a bad cpu with an internal short circuit on the clock line i think, i never found one, so i checked the trace from the oscillator to the cpu and it was good, so the coscillator should be damaged, i removed it …

… and replaced with a good one …

I powered up the game and the audio was fine! Board fixed!


A friend of mine, Daniele, gave me this board from his personal collection for a quick check-up and maintenance. As all we know CAPCOM uses on these CP SYSTEM II (CPS2) boards an anti-piracy measure protecting the game. The game code is encrypted and it’s decrypted on-the-fly by the main CPU using a special decryption key stored on a battery powered RAM. So if the battery is running out of power the decryption key is lost and the board “dies” preventing the CPU running the correct program code and obviusly the board stops working. This is why the battery who powers the special RAM is better known as “Suicide Battery”. So before the board commits its “programmed” suicide, the battery should be replaced.

Like Mr.Ozzi (a friend of mine) said, speaking about his personal arcade boards collection: “a suicide battery is like a cucumber in the a*s, the more batteries, the more cucumbers you have!“.

Here is the CPS2 board, a Japanese SUPER STREET FIGHTER 2X :

The CPS2 system is a two parts sandwich, a bottom mainboard with a black case and a top game board with a coloured case, which holds the game EPROMS and the SUICIDE BATTERY too. This game board is made in green plastic because is a japanese CPS2 but you can find them in different colours for each different region :

Region Case Version Screen
Japan Green plastic White text
U.S.A. Blue plastic Red text
Euro/Etc./World Blue plastic Blue text
Asia Grey plastic Yellow text
Hispanic Orange plastic Green text
Brazil Orange plastic Magenta text
Oceania Blue plastic Orange text
Rental (any of above) Yellow plastic (Any of above)
(Any of above) Black metal “all-in-one” (Any of above)

This table is taken from CPS2 page on Wikipedia.

Once opened the game ROM board we can see its PCB and the battery, the red one on the bottom right side, on the following photo:

Measuring the battery reveals it’s not in so good condition to power the security RAM anymore, it’s around 3.48 Volts. It’s enough to keep the game working but a new one should be around 3.6V and this is a clear signal that the battery which served this board for over 10 years il slowly depleting its power. So we must replace it, here is the new battery ready to be soldered on the PCB:

We must proceed to remove the old one desoldering its leads on the pads in the back side of the PCB:

Now there will be the “hardest” part, once removed the old battery the special RAM will remain with no power and we must hurry replacing the battery, because the battery-powered RAM will loose its contents in minutes. Some guys says 10 minutes, other guys says over 1 hour, by the way i don’t want to discover it for sure …

So if you are going to replace it tremendously really slowly you must use a helper battery for the process, but if you are a PRO there should be enough time to take a shot too … LOL !

Once removed the old battery, the new one can be soldered in its place, but be careful to install it in the proper way, the positive (+) side of the battery must go on the left side, the negative (-) side instead goes close to the edge of the PCB, like the photo below:

Solder the battery on the underside of the PCB, cut the exceding length of the leads off and make ABSOLUTELY sure that the battery is soldered properly and in the right way.

Job done … now we must test the board …

Yeah! Repeat the test and power up the board again after few hour to make sure the new battery is doing it’s job …

… if the board has committed suicide is a clear sign that something has gone wrong, but thanks to the effors of Eduardo Cruz, Artemio Urbina and Ian Court few months ago they announced the successful reverse engineering of CPS2 security protection, allowing to DE-SUICIDE and restoration of any dead games without hardware modifications.

Here is the links to their site … follow them, it’s a very interesting reading:

Eduardo Cruz (30 April 2016). Arcade Hacker: Important Capcom CPS2 Announcement.

Eduardo Cruz (13 September 2016). Capcom CPS2 Security Programming Guide.

… another case closed!


A friend of mine, Enrico, bought this boards it was sold as working but it suffers some kind of colors issue. Wrong colors are displayed on the screen, the board graphics seem to be too green and too blue. Here’s the PCB:

… and this is a video shot of the issue:

This is due to a lack of the red component in the video signal, it’s a quite common issue on mvs boards. Usually missing or incorrect colors can be caused by a damged part in the video DAC circuit. The digital part of the video output section shouldn’t be guilty this time. The parts involved causing the issue should be spotted between a pair of 74LS273 latches, a resistor network and a 74LS05 hex buffer-inverter IC.

The usual visual inspection reveals damage in a resistor in the video DAC circuit, it’s a common issue seeing this resistors failing, it’s due to Ohm’s law: the lower the resistance the higher is the current flowing through the circuit, so the resistors with lowest values are the ones which fails first:

The 150ohm resistor is burned and must be replaced, but this may be the consequence of the culprit and not the damage itself. So take a look at the video DAC circuit taken from the schematics at NeoGeoDev.Com site:

On the following picture you can also look how the RGB colors are mangled by the board:

Measuring the resistor value reports a too low value around 24ohm instead of the 150ohm needed by the circuit, but this damage should be caused by something else, so it needs further investigations.

Once replaced the resistor …

… diplaying color bars and measured the output signal intensity of the RED component with a scope the resultulting measurements reveals an unsuitable peek-to-peek value compared to other color (RGB) signals, the BLUE signal is in yellow and the RED signal is in green (LOL), it should be a perfect match:

If you look at the color bars too you can spot a slighter low brightness of the RED color signal:

Also measuring with an ohmmeter the connection between one lead of the 150ohm RED video signal resistor and ground reveals a short circuit, instead of (about) 10Mohm resistance of the GREEN and BLUE signals, this high resistance should be the internal resistance of an IC probably damaged.

Looking at the schematics only one IC can be responsible of this bad connection, so we must take care of it, it’s a 74LS05 Hex Inverter. Promptly removed from the board:

… promptly tested, ad promptly failed, the output at pin 6 is shorted to ground (pin 7) and obviusly the relative logic unit fails the test:

I replaced the IC and tested the board …. SUCCESS!

For correct color balancing i replaced all three 150ohm resistors too:

… another case closed! Enrico should be happy this time too! 🙂

By continuing to use the site, you agree to the use of cookies. MORE INFORMATION

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

To make this site work properly, we sometimes place small data files called cookies on your device. Most big websites do this too. A cookie is a small text file that a website saves on your computer or mobile device when you visit the site. It enables the website to remember your actions and preferences (such as login, language, font size and other display preferences) over a period of time, so you don’t have to keep re-entering them whenever you come back to the site or browse from one page to another.

How do we use cookies?
to remember users' actions, to identify the user login also with third-party cookies (facebook, twitter, google+, etc...) for social related tools, to enhance the performance of the website, they are session cookies, and third-party ones are used for google analytics tools. The cookies will not be used for any purpose other than the one stated.

How to control cookies:
You can control and/or delete cookies as you wish – for details, see You can delete all cookies that are already on your computer and you can set most browsers to prevent them from being placed. If you do this, however, you may have to manually adjust some preferences every time you visit a site and some services and functionalities may not work.