Sega Mega Drive / Genesis (Model 2)
 | |
| North American Genesis Model 2 with control pad | |
| Specifications | |
|---|---|
| Manufacturer | Sega Enterprises, Ltd. |
| Type | Home video game console |
| Released | 1993[1] |
| CPU | 68000 (8 MHz class) and Z80A (4 MHz class)[2] |
| Memory | 72 KB RAM; 64 KB VRAM[2] |
| Storage | — |
| Display | — |
| Sound | FM, PSG and PCM[2] |
| Graphics | Sega custom LSI VDP, 512 colours[2] |
| Media | ROM cartridge |
| Power | External DC adaptor, centre positive; 18 W[2][3] |
| Dimensions | 220 × 212 × 59 mm[2] |
| OS / Firmware | — |
| Predecessor | Sega Mega Drive / Genesis (Model 1) |
| Model no. | MK-1614, MK-1630 (Genesis II); MK-1630, MK-1685, MK-1686, MK-1695 (Mega Drive II)[3] |
The Sega Mega Drive II, sold in North America as the Genesis (Model 2), is the smaller and cheaper redesign of Sega's 16-bit console, introduced in 1993. It drops the Model 1's headphone socket and replaces the 8-pin DIN A/V socket with a smaller connector that carries stereo sound, and it has a simpler mainboard that uses less power.[1] Sega's service manual for the Genesis II and Mega Drive II, No. 001, is dated June 1993.[2]
Hardware
[edit | edit source]| Item | Specification |
|---|---|
| CPU | 68000 (8 M) and Z80A (4 M) |
| RAM | 72 KB |
| VRAM | 64 KB |
| Audio | FM, PSG, PCM |
| VDP | Sega custom LSI |
| Colours | 512 |
| Video outputs | Video and RGB |
| Control terminals | 2 |
| Power input | AC 120 V 60 Hz (Genesis II); AC 220 V or 240 V 50 Hz (Mega Drive II) |
| Power consumption | 18 W |
| Dimensions | 220 (W) × 212 (D) × 59 (H) mm |
| Operating environment | 5–35 °C, 20–80% RH, non-condensing |
The specification is from page 3 of Sega's manual.[2]
Main board ICs
[edit | edit source]| Position | Part | Notes |
|---|---|---|
| IC1 | 68000: HD68HC000CP8 or MC68HC000FN8 (PLCC) | |
| IC2, IC3 | 32K × 8 static RAM | Work RAM. On VA1, IC2 is a single 64K × 16 part and IC3 is not fitted[4] |
| IC4 | Z80: Z84C0006 or TMPZ84C00AU; or Sega 315-5676 (NEC µPD9033GB) on PAL and RGB boards | |
| IC5 | 8K × 8 static RAM | Z80 RAM |
| IC6 | Sega custom chip FC1004 (315-5660) | There is no separate VDP or YM2612 in the parts list |
| IC7, IC8 | 64K × 4 video RAM (ZIP) | On VA1, IC7 is a single larger part and IC8 is not fitted[4] |
| IC9, IC10 | LM324 or BA10324AF op-amps | Replaced by one 315-5684 on VA2, VA2.3, VA3 and VA4 boards[5][6] |
| IC11 | RGB encoder: MB3514PF, CXA1145M or KA2195D | See below |
| IC12 | 7805 regulator: µPC7805HF or TA7805S | |
| OSC1 | 53.693175 MHz (NTSC) or 53.203424 MHz (PAL, RGB) | |
| D2 | 1SR-35-100A | In the DC input |
The table is from Sega's electrical parts list.[2]
Encoder types
[edit | edit source]The first page of Sega's manual says that parts of the Genesis II circuit differ according to the RGB encoder fitted at IC11, and tells the technician to identify it first:[2]
| Type | Encoder | Sega part |
|---|---|---|
| F | MB3514PF-G-BND-EF | 313-5232-A |
| S | CXA1145M-T6 | 313-5213-A |
| SM | KA2195D | 313-5236-A |
The Mega Drive II (PAL and RGB) uses the type F encoder. The encoder type decides the value of CE14 (220 µF on type F and the Mega Drive II, 10 µF on types S and SM) and whether several coils, resistors and ceramics round the video output are fitted.[7]
Board revisions
[edit | edit source]| Revision | Changes | Source |
|---|---|---|
| VA0 | Boards 837-9602-F, -S and -SM (USA) and 837-9603 (Europe). Separate IC2 and IC3 work RAM, separate IC7 and IC8 video RAM | Sega[2] |
| VA1 | Boards 837-9793 (USA) and 837-9794 (Europe). IC2 becomes one 64K × 16 RAM and IC3 is deleted; IC7 becomes one part and IC8 is deleted; CE33 (47 µF 10 V) added on PAL boards; C11, C30, C61, C63, R42–R45 and R81 change | Sega[4] |
| VA1.8 | Console5 lists IC6 315-5660 and a single video RAM at IC7 | Console5[8] |
| VA2.3 | IC6 315-5786, a separate YM2612 at IC8, 315-5684 at IC9 and a CXA1645M encoder | Console5[8] |
| VA3 | USA boards 837-10150. "IC9 and IC10 have been integrated into one chip": a single 315-5684 (Rohm BA6166FS) at IC9, IC10 deleted, surrounding circuit changed and the board made slightly smaller | Sega[5] |
| VA4 | One ASIC, 315-5960, for the CPUs and sound; 315-5684 at IC4, CXA1645M encoder at IC5, 7805 at IC6 | Console5[8] |
Sega assigned four service part numbers for IC6, and its December 1993 supplement gives a table of which of C1, C4 and C15 to fit with each. Check it when replacing IC6.[4]
Connectors
[edit | edit source]| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | Blue | 6 | Audio (mono) |
| 2 | Vcc | 7 | Red |
| 3 | Green | 8 | Stereo left |
| 4 | Composite video | 9 | Stereo right |
| 5 | Composite sync | Shell | Ground |
The pin assignment is from Sega's Mega Drive II schematic and matches the A/V OUT connector (CN4) in Sega's 32X service manual.[9][10]
The other connectors are CN3, the 64-pin edge connector (Sega 209-5061, PSB4D32K-7R); CN5, the two controller ports (D-sub 9-pin × 2); and CN7, the DC jack, an EIAJ-3 type (Sega 212-5353).[2]
Power
[edit | edit source]The DC jack CN7 feeds the common-mode filter CF1, the power switch S2 and the diode D2 to CE16 (220 µF 16 V) and the 7805 at IC12.[9] The plug is centre positive, the opposite of the Model 1, and smaller; Model 1 adaptors must not be used.[11]
| Part | Rating | Market |
|---|---|---|
| 400-5135A (and -01, -02, -03) | AC 120 V in, DC 10 V 0.85 A out | Genesis II |
| 400-5209 | AC 230 V 50 Hz in, DC 10 V 0.85 A out | Mega Drive II except UK, Australia and New Zealand |
| 400-5208 | AC 240 V in, DC 9 V 0.85 A out | Mega Drive II, UK |
| 400-5211 | AC 240 V in, DC 9 V 0.85 A out | Mega Drive II, Australia and New Zealand |
The adaptors are from the accessories lists in Sega's manual.[3] Sega's 32X manual lists the same part numbers for the 32X, but gives 400-5208 as 10 V DC.[10] Read the label on your own adaptor.
Servicing
[edit | edit source]The Model 2 numbers its electrolytic capacitors in a separate CE series; plain C numbers are ceramics.[2] Lists for each board are in the Sega Mega Drive / Genesis (Model 2) Capacitor Replacement Guide. There is one 7805 regulator (IC12). See also the Sega Mega Drive / Genesis (Model 2) Maintenance Guide and the Sega Mega Drive / Genesis (Model 2) Troubleshooting Guide.
Documentation
[edit | edit source]- Sega Service Manual - Genesis II / Mega Drive II - June 1993: the full manual, No. 001
- Sega Service Manual Supplement - Genesis II / Mega Drive II - August 1993: No. 001-1
- Sega Service Manual Supplement - Genesis II / Mega Drive II - December 1993: No. 001-2, differences between Ver.0 and Ver.1
- SEGA Genesis Model 2 VA3 Service Manual: No. 001-3, August 1994
- Sega Mega Drive 2 / Genesis 2 VA0 Service Manual
Gallery
[edit | edit source]-
Genesis Model 2 main board, PC BD MD2 VA0 USA -
Sega's parts-location drawing for the PAL VA0 board
References
[edit | edit source]- ↑ 1.0 1.1 Sega Genesis, Wikipedia (accessed 2026-10-01), section on the Model 2.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 Service Manual, Genesis II / Mega Drive II (PAL-B/I/G, RGB), No. 001, Sega Enterprises, June 1993, section 1 "Specifications" (PDF p. 3), "Before using this service manual" (PDF p. 2) and section 8-3 electrical parts list (PDF pp. 29–36). See Sega Service Manual - Genesis II / Mega Drive II - June 1993.
- ↑ 3.0 3.1 3.2 Service Manual, Genesis II / Mega Drive II, No. 001, June 1993, section 8-4 accessories and package lists (PDF pp. 37–38).
- ↑ 4.0 4.1 4.2 4.3 Service Manual Supplement, Genesis II / Mega Drive II (PAL-B/I/G, RGB), No. 001-2, Sega Enterprises, December 1993, section 1-2 "Difference Table and Parts List" (pp. 3–4). See Sega Service Manual Supplement - Genesis II / Mega Drive II - December 1993.
- ↑ 5.0 5.1 Service Manual, Genesis II VA3, No. 001-3, Sega Enterprises, August 1994, section 1 "Differences" and parts list. See SEGA Genesis Model 2 VA3 Service Manual.
- ↑ Darren Wershler and Ace, "Forensics: Genesis 2 with original Mega Amp", Residual Media Depot (accessed 2026-10-10): the 315-5684 replaces the two quad op-amps of the VA0, VA1 and VA1.8 boards and is used on VA2, VA2.3, VA3 and VA4.
- ↑ Service Manual, Genesis II / Mega Drive II, No. 001, June 1993, section 5-3 schematic diagram 3 with the difference table for diagram 4 (PDF p. 10), and the electrical parts list (PDF pp. 29–36).
- ↑ 8.0 8.1 8.2 Mega Drive II / Genesis 2, Console5 TechWiki (accessed 2026-10-01): chip lists for VA1.8 (USA and PAL), VA2.3, VA3 and VA4, and capacitor lists for VA0 to VA4.
- ↑ 9.0 9.1 Service Manual, Genesis II / Mega Drive II, No. 001, June 1993, section 5-4 schematic diagram 4 (PDF p. 11): CN1, CN5, CN6 and the DC input CN7.
- ↑ 10.0 10.1 Service Manual, Genesis 32X / Mega Drive 32X, No. 012, Sega Enterprises, June 1995, schematic (PDF p. 12): A/V OUT connector CN4; parts list: CN8 DC jack 212-5353 and AC adaptors. See Sega Genesis 32X / Mega Drive 32X Service Manual.
- ↑ Dave Farquhar, "Sega Genesis power supply specs", The Silicon Underground, 24 July 2019.