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Mega Drive Maintenance Manual - PAL-G, August, 1992, Rev. A

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The Mega Drive Maintenance Manual, PAL-G (Germany) is Sega Enterprises, Ltd.'s 107-page maintenance manual for the original Mega Drive, dated August 1992, Rev. A. It covers the German PAL-G machine on two main-board revisions, IC BD M5 VA4 and IC BD M5 VA6.5 (the latter Sega part 837-8779), with the two sub-boards fitted to them. The scan has a text layer, though the OCR of the parts lists is poor.

Contents

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Sega's contents list is on pages 2 and 3 of the PDF. The scan does not follow its order exactly; the PDF page on which each section starts is given here.

Section PDF page What it covers
1. Block diagram 4 The whole machine on one sheet
2. Assembly drawing 6 2-1 general reference number list (with VA4 and VA6.5 quantity columns); 2-2 assembly lists for 1001 top case assembly 1, 1002 top case assembly 2, 1003 shield plate top assembly and 1004 main board assembly; 2-3 disassembly and assembly procedure (p. 18)
3. Spare parts list 20 Headed "for PAL-G & PAL-I"
4. Accessories list 22
5. PCB repair procedure 24 Repair flow chart and a phenomenon-and-cause list: no power, picture problems, sound problems (including the VER.0 power-on drum sound blamed on the IC7 static RAM) and pad faults. It names the custom chip at IC4 by board version: VER.0, 1 and 2 use 315-5308, VER.4 315-5364, VER.5 315-5402 and VER.6 315-5433 (pp. 30-31). For pad faults it names 315-5409 on VER.0, 1, 2 and 4 (p. 35); the VA4 parts list has IC4 as 315-5364 (YM6045C) and IC5 as 315-5309 (YM6046) (p. 84)
6. Soft and hard check manual 36 Check-cartridge procedure and the Genesis hard checker error list (p. 44)
7. Parts specification 46 Pin and function data for IC1 (SCN68000C8N64), IC3 (µPD42832C-15), IC6 (Z80A), IC7 (µPD4364C-15), IC8 (YM7101, 315-5313A), IC11 (YM2612) and IC13 (CXA1145P)
9. Schematic diagram 64 PC BD M5 PAL-G VA4 main and VA6.5 main, four sheets
11. PCB design spec. 69 Component-side and solder-side marking and copper layers for the VA4 and VA6.5 boards
10. Mount diagram 74 Main and chip mount diagrams for the VA4 and VA6.5 boards
8. Parts list of PCB 83 Electrical parts lists for IC BD M5 VA4, IC BD M5 VA6.5 (837-8779, from p. 99), ASSY SUB BOARD3 M5 (839-0262) and ASSY SUB BOARD M5 (839-0199)

What this manual settles

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  • The M5 main board numbers its capacitors in one interleaved C sequence and has no CE series. Electrolytics sit in the same run as ceramics: on the VA6.5 list C41 and C57 are 10 µF 16 V (Sega 150-0023), C44 and C61 are 1 µF 50 V (150-0009), C52 is 100 µF 10 V (150-0047), C63 is 47 µF 10 V (150-0062) and C50 and C51 are 220 µF 10 V (150-0126). The Model 2, 32X, Saturn and Dreamcast use a separate CE series instead.
  • The parts lists state the dielectric twice: the description reads CAP E or CAP CER, and the part number is in Sega's 150-xxxx series for electrolytics and 151-xxxx for ceramics. Neither depends on the designator.
  • Sega describes every electrolytic on the board as "U-TYPE".
  • The PCB repair flow chart (PDF p. 28) gives the go/no-go checks in order: voltage at the power switch; VCC1 and VCC2 at +5 V from IC15 and IC17 (both 7805); the crystal oscillating; VREF at about 2 V from IC13 (CXA1145); and MRES reaching 5 V within 1.6 seconds.

What this manual does not contain

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  • Coverage of NTSC Genesis boards or of board versions other than VA4 and VA6.5. The title page reads "PAL-G (GERMANY)".
  • Anything on the Model 2 console, the Mega CD or the Sega 32X.
  • A table of rail voltages or tolerances. Beyond the checks in the flow chart, the repair procedure names suspect parts without measured values.

Pages that cite this document

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Download: Mega Drive Maintenance Manual - PAL-G, August, 1992, Rev. A.pdf

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