This is the sole motherboard revision for the Sega Mark III, the original Japanese version of the Sega Master System. Like most previous Sega console motherboards, it is a single-sided PCB made of phenolic resin, and reuses a number of parts from the SG-1000 line. By the end of 1987, Sega discontinued the Mark III in favor of a slightly upgraded variant of the international Master System, albeit one compatible with Japanese 44-pin cartridges.
In late 1988, a company known as Korea OACS began distributing the Mark III in South Korea, and this version of the console uses the 171-5304 board revision like its Japanese counterpart. However, it uses a different RF modulator and the card slot was completely omitted, meaning that Sega Card games and the 3D glasses adapter are incompatible.[1]
Parts List
All resistors are 1/4 W.
| Designation | Value/Name | Notes |
|---|---|---|
| C1 | 10 uF 16V | |
| C3 | NP | |
| C4 | 22 nF | |
| C5 | 100 uF 10V | |
| C6 | NP | |
| C7 | 22 nF | |
| C8 | 100 uF 10V | |
| C9 | 22 nF | |
| C10 | NP | |
| C14 | 33 pF | |
| C15 | 33 pF | |
| C18 | 10 uF 16V | |
| C22 | 10 uF 16V | |
| C23 | 22 nF | |
| C25 | 22 nF | |
| C27 | NP | |
| C29 | NP | |
| C30 | NP | |
| C31 | 22 nF | |
| C32 | NP | |
| C46 | 2.2 nF | |
| C47 | 2.2 nF | |
| C48 | 2.2 nF | |
| C49 | 2.2 nF | |
| C50 | 2.2 nF | |
| C51 | 2.2 nF | |
| C52 | 2.2 nF | |
| C53 | 2.2 nF | |
| C54 | 2.2 nF | |
| C55 | 2.2 nF | |
| C56 | 2.2 nF | |
| C57 | 2.2 nF | |
| C60 | 22 nF | |
| C62 | 82 pF | |
| C65 | 33 pF | |
| C66 | 18 pF | |
| C68 | 1 uF 50V | |
| C69 | 47 nF | |
| C70 | 1 uF 50V | |
| C72 | 270 pF | |
| C77 | 1 uF 50V | |
| C79 | 270 pF | |
| C84 | 1 uF 50V | |
| C86 | 1 uF 50V | |
| C90 | 1 uF 50V | |
| C93 | 1 uF 50V | |
| C96 | NP | Should be populated with 10 uF capacitor to GND to terminate pin 20 of BA7230LS |
| C98 | 10 uF 16V | |
| C99 | 22 nF | |
| C102 | 18 pF | |
| C106 | 47 uF 10V | |
| C108 | 22 nF | Has pads for an electrolytic cap, populated with non-polarized axial capacitor instead |
| C109 | 10 uF 16V | |
| C110 | NP | Has pads for either an electrolytic or non-polarized axial capacitor |
| C111 | NP | |
| C113 | 33 pF | |
| C114 | 47 uF 10V | Has a pad for a non-polarized axial capacitor, populated with electrolytic capacitor instead |
| C115 | 47 uF 10V | Has a pad for a non-polarized axial capacitor, populated with electrolytic capacitor instead |
| C116 | 47 uF 16V | |
| CA1 through 35 | 18-pin header (Japan) NP (Korea) |
Wire harness for 171-5305 board, odd-numbered pins |
| CB2 through 36 | 18-pin header (Japan) Wire link on CB2 and CB36 (Korea) |
Wire harness for 171-5305 board, even-numbered pins |
| CON1 | 9-pin D-sub connector | 2P port |
| CON2 | 9-pin D-sub connector | 1P port |
| CON3 | 44-pin edge connector, 3.18 mm pin pitch | Same as used in the SG-1000 II |
| CON4 | 37-pin edge connector | Mounted on 171-5305 |
| CON6 | 8-pin DIN connector, 262 degree | Carries composite video, mono audio and (unamplified) RGBS |
| CON7 | 5.5 x 2.1 mm barrel jack | |
| D21 | 1S2473 | |
| IC1 | NEC D780C-1 (Japan) Goldstar Z8400A PS (Korea) |
CPU |
| IC2 | NEC D4168C-15 | Z80 RAM |
| IC3 | Sega 315-5124 / Yamaha YM2602 | VDP |
| IC4 | NEC D4168C-12 | VRAM |
| IC5 | NEC D4168C-12 | VRAM |
| IC6 | ROHM BA7230LS | Video encoder |
| IC7 | 7805 | |
| IC8 | Fujitsu MB74LS257 (Japan) Goldstar GS74LS257 (Korea) |
|
| IC9 | Fujitsu MB74LS257 (Japan) Goldstar GS74LS257 (Korea) |
|
| IC10 | Fujitsu MB74LS32 (Japan) Goldstar GS74LS32 (Korea) |
|
| J1 | NP | |
| J2 | Wire link | |
| J3 | NP | |
| JG | Wire link | |
| JV | Wire link | |
| L64 | 56 uH | |
| PAUSE SW | Sega 509-5031 | Same as used in the SG-1000 line |
| POWER SW | Unknown | Same as used in the SG-1000 line |
| Q13 | 2SC1740 | |
| Q74 | 2SC1740 | |
| Q81 | 2SC1740 | |
| Q103 | 2SC1740 | |
| R1 | 220 ohm | |
| R2 | 68 ohm | |
| R11 | 10k ohm | |
| R12 | 560 ohm | |
| R17 | 2.2k ohm | |
| R19 | 270 ohm | Mounted vertically |
| R20 | 100k ohm | |
| R24 | 2.2k ohm | |
| R26 | 2.2k ohm | |
| R28 | 2.2k ohm | |
| R58 | 3.3k ohm | |
| R59 | 10k ohm | Mounted vertically |
| R61 | 1.2k ohm | |
| R63 | 270 ohm | |
| R67 | 470 ohm | |
| R71 | 1k ohm | |
| R73 | 3.3k ohm | |
| R76 | 270 ohm | |
| R78 | 1k ohm | |
| R80 | 3.3k ohm | |
| R83 | 270 ohm | |
| R85 | 3.3k ohm | |
| R87 | 3.3k ohm | |
| R89 | 3.3k ohm | |
| R91 | 3.3k ohm | |
| R92 | 3.3k ohm | |
| R94 | 3.3k ohm | |
| R95 | 1.5k ohm | Mounted vertically |
| R97 | NP | Should be populated with at least a wire link to GND to terminate pin 20 of BA7230LS |
| R100 | 560 ohm | |
| R101 | 10k ohm | |
| R104 | 8.2 ohm | Mounted vertically |
| R105 | 560 ohm | |
| R107 | 2.2k ohm | |
| R112 | 1.2k ohm | |
| RA1 | 4.7k ohm 7-pin array | |
| RA2 | 4.7k ohm 7-pin array | |
| RF.MOD | Mitsumi VJ1221 (Japan) Jalco MGB3-VU3401 (Korea) |
|
| XTAL | 10.7386 MHz | |
| Unmarked | 0.1 uF | Soldered across IC5, unmarked footprint is unpopulated |
| Unmarked | 180 pF | Soldered near IC1 |
171-5305 Parts List
This is the small board which has the card slot, and is connected to the motherboard through two wire harnesses on connectors CA and CB. It is screwed into the top case, with the card slot being secured with screws and nuts. This board was entirely omitted on the Korea OACS Mark III and CB2 and CB36 on the main board were bridged.
| Designation | Name/Value | Notes |
|---|---|---|
| C3 | NP | |
| C4 | 47 uF 16V | |
| C5 | NP | |
| CON4 (on motherboard) | Sega 209-5020 | |
| D2 | Red rectangular LED | Power LED, has a small plastic spacer |
| R1 | 220 ohm |