Neo Geo CD 50/60Hz Mod
This mod is for the NEO GEO CD top-loading unit and allows you to switch your unit from NTSC to PAL or vice versa. It has been tested, and it works neatly.
** Before opening your Neo Geo CD console please read the whole document to avoid serious damage to your machine! **
PAL -> NTSC conversion
[ STEP 1 ] Open up your Neo Geo CD unit by unscrewing the four screws found on the bottom of the machine. Use a Philips screwdriver to avoid damaging the screws. Remove the cover by carefully lifting it on the back (where the video ports are) and pay attention to the controller ports. After the cover is loose, remove the white plastic cable connect ing the top cover (which includes the CD ROM unit) and put the cover aside.
[ STEP 2 ] Look at Picture 1 below. You see resistor slot R47, resistor slot R52 and jumper wire JN1 on the left to R52. These three spots on the video pcb (pcb = printed circuit board) have to be modified in order to adjust the color sync from PAL to NTSC.
[ STEP 3 ] Disconnect all interface cables connecting the video pcb with the main board which resides underneath a brownish plastic shielding. Unscrew the video pcb (Picture 1) and remove it from the console. Then solder out the 16K resistor R47 and replace it with a 20K one. You should be able to get these resistors from any shop for electronic supplies.
[ STEP 4 ] Cut the jumper wire JN1 with a pair of scissors or nippers. Be careful not to damage the pcb, and don't use too much force.
[ STEP 5 ] Unscrew the connector pcb (where the joy ports are). Unscrew the brownish shielding and carefully remove the main board. On the back of the main b oard you will see the tiny jumper bay R26 (see Picture 2 below). Remove the jumper (which is in fact very tiny!). This sets the display ratio from 50Hz to 60Hz thus eliminating the PAL borders.
[ STEP 6 ] Replace the main board, tighten the screws, then reattach the shielding, the control and video pcb, and reconnect all interface cables to the main board. Finally, put the top cover back on and connect the white plastic interface cable from drive unit to the console, and tighten its screws.
Done.
NTSC -> PAL conversion
[ STEP 1 ] Open up your Neo Geo CD unit by unscrewing the four screws found on the bottom of the machine. Use a Philips screwdriver to avoid damaging the screws. Remove the cover by carefully lifting it on the back (where the video ports are) and pay attention to the controller ports. After the cover is loose, remove the white plastic cable connect ing the top cover (which includes the CD ROM unit) and put the cover aside.
[ STEP 2 ] Look at Picture 1 above. You see resistor slot R47, resistor slot R52 and jumper wire JN1 on the left to R52. These three spots on the video pcb (pcb = printed circuit board) have to be modified in order to adjust the color sync from NTSC to PAL.
[ STEP 3 ] Disconnect all interface cables connecting the video pcb with the main board which resides underneath a brownish plastic shielding. Unscrew the video pcb (Picture 1) and remove it from the console. Then solder out the 20K resistor R47 and replace it with a 16K one. You should be able to get these resistors from any shop for electronic supplies. Now solder out resistor R52 and discard or save it for switching back to NTSC.
[ STEP 4 ] Insert a jumper (a short piece of wire) into slot J N1 thus closing the connection between the two holes.
[ STEP 5 ] Unscrew the connector pcb (where the joy ports are). Unscrew the brownish shielding and carefully remove the main board. On the back of the main board you will see the tiny jumper bay R26 (see Picture 2 above). Insert a jumper here or attach a small wire which connects the two poles of the jumper. The jumper has to be closed (position HIGH (H)) in order to switch your console from 60Hz to 50Hz.
[ STEP 6 ] Replace the main board, tighten the screws, then reattach the shielding, the control and video pcb, and reconnect all interface cables to the main board. Finally, put the top cover back on and connect the white plastic interface cable from drive unit to the console, and tighten its screws.
Done.
N.B.: If you don't care for a color adjustment or your TV shows blurry graphics after the mod, just open/close jumper R26 on the back of the main board without fiddling with the resistors. This way, only the display ratio gets converted from 50Hz to 60Hz or vice versa, without modifications to the color sync.
History of the Neo Geo CD
In the mid 1990s SNK corporation found itself with an extremely popular and successful arcade system in the Neo Geo MVS. Its games were hot items and arcade ops were buying lots of them! However, do to the high price tag of the home console games, they were never as successful as their arcade counterparts.
On Sept. 4, 1994 in Japan SNK decided to try and change all that. Enter the Neo Geo Cd-rom system.
Although the units price was still high at $500, SNK hoped that the inexpensive compact disc format would bring in the buyers. Instead of charging $200+ per game SNK would be able to sell CD versions for a fourth of the price. This allowed them to compete with the more successful consoles of the time. It was released in limited numbers with a front "power" loading CD tray. This version was quickly replaced with the less expensive "top loader". The CD system is almost the exact same hardware as its cartridge based counterparts. It had only two really noticeable limitations. The first was that since it wasn't using a ROM cart it had to use direct memory to store data that it read off the game disks. SNK decided on 56 Mbits.
This was a lot of memory for the time, but no amount of memory can compete with the speed of ROM access. This resulted in the larger games having some animation and scenes being cut out so that the games could work within the systems limited memory space. A limitation not shared by the cartridge based Neo Geo systems. To make up for this, SNK usually did a nice job remixing the audio for CD releases. They also sometimes add in artwork galleries as another bonus. This is a very nice feature that Home cart & MVS users miss out on. The second problem with the CD system was that it came with a single speed Cd-rom drive. Since Neo games tend toward large megabit sizes, the result was very long load times. Most of the older, smaller games have less loading time and play fine. The newer larger games (especially fighters) tend to have longer loading time. This delay is enough that many feel it detracts so much that the games are just not worth the frustration. SNK recognized this too late, but they did try to correct it.
Their efforts took form as the Neo Geo CDZ system. This console is the same except that it has a larger cache and better CD head controller. This has the end result of faster/shorter load times.
A blessing for CD fans, but unfortunately this console was released in limited numbers in Japan only.
Therefore it is a hot import item. I have heard many say that the CDZ is not as mechanically reliable as its slower sibling, but as I have never owned one I really can't say for sure.
Specs:
Processor: Motorola 68000 (12 Mhz), Zilog-80A (4 Mhz)
Resolution: 320x224
Color Palette: 65,536
Maximum Colors On-Screen: 4,096
Maximum Sprites On-Screen: 380
Minimum Sprite Size: 1x2
Maximum Sprite Size: 16x512
Maximum Planes: 3
Sound Channels: 15 (7-Digital, 4-FM synthesis, 3-PSG, 1-Noise channel)
Internal RAM: Work RAM: 56 Mbits + 64 kb cache, Video RAM: 512 Kb Z80 RAM: 2 Kb
Cd-rom Drive: 1X (Cdz version has bigger/faster cache)
Save Memory: 56 Mbits
