NEO GEO AND XRGB-3
First, it's necessary to install the LM1881 on video circuit. I chose to plug it on the RGB cable, but this may also be done on the Neo Geo itself or on the XRGB-3 board. Simpler and less risky, I highly recommend you to choose the solution of soldering it on the cable.
Question: what is exactly this LM1881 and why is do we need it? On many Neo Geo machines, the video signal is often too strong and can cause losses of sync (image jumping, unstable picture or black screen for a few seconds) and it happens when displaying a very clear or white picture, or simply when the screen flashes (King of Fighters, or just a lightning in a game). This does not necessarily happen on most of our CRTs, but more frequently on our flat screens devoid of sync separator (unlike monitors). This small chip, once introduced into the circuit of our video installation, will permanently resolve this problem.
Below you will find the assembly plan for the LM1881 sync separator, plus the diagram showing the position and role of the different pins on the japanese RGB, and a photo of the finished assembly. There is very little welding to do, and you can put the installation in a small plastic box for a more 'clean' result, it's up to you.
PRISE RGB 21 PIN JAP PLAN
1 Left audio output 2 Audio input ground 3 Audio output ground 4 Right audio input 5 Right audio output 6 Sync input ground 7 Sync output ground 8 Sync input 9 Sync output 10 AV control signal 11 RGB video signal mask (Ym) 12 Red ground 13 Ym/Ys ground 14 Red 15 Video signal switch (+5v) 16 Green ground 17 Blue ground 18 Green 19 BlueGround 20 Ground
LM1881 ASSEMBLY DIAGRAM
Another important step, is the update of the XRGB-3 and installation of the firmware in English (except for lucky people who can read Japanese, of course) and especially the B1 firmware to enable the use of scanlines on the picture.. . Essential!
The process is quite simple. Connect the XRGB to your PC via an USB cable. Windows will detect and install the upgrade tool automatically. You see, the interface buttons are in Japanese, but you just have to confirm with the highlighted button every time. To set your interface in English, update with the "B0 FIRMWARE v2.12 file (ENGLISH). Then also update the "B1 FIRMWARE v1.00 file (JAPANESE). This will integrate the scanlines into the picture settings menu. Restart the XRGB for the changes to take effect.
Once the XRGB-3 LM1881 Update and installed the equipment is complete and ready to be used. Connect the SCART changed with the LM1881 in the entry "IN GAME" in front of the camera. At the back of it, connect the VGA cable OUT ANALOG DISPLAY (see photo). On your TV, plug the VGA on the socket. Then plug the power supply 3 X-RGB converter on your 110/220. Well, it's ready! It is now that we will play a bit with the remote ...
Turn the XRGB, switch your TV on RGB channel (or VGA, depending on screens) and turn on the console. If your connection is correct, you should have an image, even a bad one. If this is not the case, try other resolutions by navigating with the buttons corresponding to the green arrows on the front. The remote is fully translated on the XRGB guide that we printed at the beginning of the procedure, consider the use if needed. The first step is to switch the XRGB-3 on B1 mode, which will allow us to use scanlines and reduce the lag within one frame, ie totally imperceptible. Rendering performance will also depend on your screen at this level, the response time being of course an important part on the outcome. For the moment, let's make the basic adjustments. A single row of four buttons will allow us to perform all our settings with the remote control: