Sega 32X Service Bulletins

The Sega 32X service bulletins are four service bulletins issued by the Quality Assurance Division of Sega between December 1994 and April 1995, scanned as one 8-page PDF with a text layer. Three of them deal with Sega 32X faults that Sega traced to the host Mega Drive Model 1 board and fixed there; the fourth records a change to the 32X's own main board. Each names a fault, gives Sega's stated reason and prescribes a board modification, with a drawing.

**Bulletins in the PDF**
No.	Date	Model	PDF pages	Subject
008	13 December 1994	Mega Drive 1 VA4, PAL	1-2	Screen shake, slowed game sound and lock-ups with the 32X
011	16 March 1995	Genesis 32X and MD 32X	3-4	Two capacitors, C96 and C97, added when IC4 is the standard cell array version
012	28 March 1995	MD 32X / MD 1 (VA4)	5-6	Lock-ups with the 32X on a VA4 Mega Drive
014	12 April 1995	32X / MD1 (VA 6.0, 6.5, 6.8)	7-8	Lock-ups with some 32X units on VA6 Mega Drives

Bulletin 008: Mega Drive 1 VA4 (PAL) screen shake

Sega says that with a VA4 Mega Drive and the 32X at room temperature, some ICs and capacitors warm up and the screen shakes, game sound slows down and games freeze. The fix improves the shape of the EDCLK signal on the Mega Drive board:

Change C92 from a 51 pF capacitor to a 33 pF ceramic capacitor, located next to IC4.
Remove FB7 and fit a jumper wire in its place, or short it out.
Remove C112, a 33 pF ceramic capacitor added to the back of the board and connected to the top of C19.
On the back of the board, add a jumper from the top of C10 (electrically the same point as IC4 pin 31) to ground. Sega recommends the middle pin of EM16 and wire slightly heavier than AWG28 (0.38 mm).

Bulletin 011: C96 and C97 on the 32X main board

A standard cell array (SCA) version of IC4 replaced the gate array originally fitted to the 32X, and two capacitors, C96 and C97, were added with it. Their value depends on the part number of IC1 and IC2:

IC1 and IC2	C96 and C97 with SCA IC4	With gate array IC4
315-0922	47 pF	Not installed
315-0922A	47 pF or 100 pF	Not installed
315-0988	100 pF	Not installed

The 32X VA2 board has two 100 pF capacitors built in; on VA0 and VA1 boards they are added according to the table. The drawing (on IC BD MARS MAIN VA0) shows C96 fitted between IC1 pin 72 and C51, C97 between IC2 pin 72 and C47, and a track cut near pin B8 of the ribbon cable connector CN2.

Bulletin 012: lock-ups on Mega Drive 1 VA4

Sega identifies the VCLK signal as the cause. Remove C78 and C100 from the VA4 Mega Drive board, and also carry out the bulletin 008 screen-shake modification, which Sega says helps with the lock-ups too.

Bulletin 014: lock-ups on Mega Drive 1 VA6.0, 6.5 and 6.8

Again the VCLK signal. Remove C78 from the Mega Drive board and fit a jumper from IC1 pin 15 to the signal side of the C78 pad. The drawing is captioned in Japanese as the modification for MD1 VA5 and VA6.

What these bulletins settle

Screen shake, slowed sound or lock-ups on a 32X used with a VA4 or VA6 Mega Drive are, in Sega's account, a host-board problem, and the fixes are made to the Mega Drive. Identify the host board revision before working on the 32X.
On the VA4 Mega Drive C92 is 51 pF as fitted at the factory and 33 pF after bulletin 008.
C96 and C97 are present only on 32X boards with the SCA version of IC4 or on VA2 boards.

What these bulletins do not contain

Schematics, parts lists or a general fault tree for the 32X. Those are in the Sega Genesis 32X / Mega Drive 32X Service Manual.
Modifications for Mega Drive boards other than VA4 and VA5/VA6, or for the Model 2.

Pages that cite this document

Download: Sega 32X Service Builletins.pdf

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