Jump to content

Sega Master System II Controller Port Repair

From RetroTechCollection
Sega Master System II controller port schematic
Sega's controller-port circuit for the PAL board 171-5922A: CN3 (player 2) and CN2 (player 1), each signal line through an EMI filter, with 330 Ω resistors in the TH and TR lines, beads in the ground lines, and the joypad inputs of the gate array IC4

The two control-pad sockets of the Sega Master System II are nine-pin D connectors, CN2 for player 1 and CN3 for player 2. On Sega's PAL schematic each signal line and the 5 V line of a socket passes through an EMI filter on its way to the board (EM11 to EM18 for CN2, EM21 to EM28 for CN3). The TH and TR lines (pins 7 and 9) also pass through a 330 Ω resistor (R5 and R6 on CN2, R7 and R8 on CN3), and the ground pin, 8, reaches the board's ground through a bead (FB1 on CN2, FB2 on CN3). The direction and button lines end at the gate array IC4.[1][2]

Sega's troubleshooting guide lists the parts on this path as the causes of a pad that does not respond: the socket, soldering, a cut track, the EMI filter, the 330 Ω resistor and the IC, with a continuity check from the socket pins to IC4.[3] The procedure below follows each line from the socket to IC4 and repairs the break or short.

Symptoms

[edit | edit source]

Sega divides the faults into two groups:[3]

Controller faults in Sega's guide
Symptom Kind of fault Where
Game does not start; a button does not respond; no response at all An open circuit Socket, joints, track, EMI filter, 330 Ω resistor, IC
Demonstration screen does not appear; a button stays pressed; a direction stays held; the game starts by itself A short circuit Socket, solder bridge, track, IC4

Rule out the pad first. Sega's own list for a pad that does not work names a cut cable, a bad connection at the plug, a cut track, faulty conductive rubber and soldering; for a pad that moves by itself, a shorted cable, greasy solder and stuck conductive rubber.[4] Try a pad that works on another console, and try the suspect pad in the other socket. A fault that follows the pad is in the pad; a fault that stays with one socket is in the console.

The Pause button is a switch on the console, not on the pad; see the Sega Master System II Troubleshooting Guide.

Tools and parts

[edit | edit source]
  • A known-good control pad.
  • Multimeter with a continuity range.
  • Phillips screwdriver, soldering iron, desoldering pump or braid.[5]
  • Replacement parts as needed: EMI filters (Sega 271-0007, STX222MB, for every position except EM17 and EM27, which are 271-0006, STB271KB), 330 Ω resistors, or a nine-pin D-sub socket (Sega 209-5017).[2]
Controller socket pins (Sega PAL schematic)
Pin Signal Player 1 (CN2) path IC4 pin, player 1 Player 2 (CN3) path IC4 pin, player 2
1 Up EM11 10 EM21 15
2 Down EM12 11 EM22 16
3 Left EM13 12 EM23 17
4 Right EM14 13 EM24 18
5 +5 V EM15 to Vcc – EM25 to Vcc –
6 TL (button 1) EM16 14 EM26 19
7 TH R5 (330 Ω), EM17 21 R7 (330 Ω), EM27 23
8 Ground FB1 to ground – FB2 to ground –
9 TR (button 2) R6 (330 Ω), EM18 20 R8 (330 Ω), EM28 22

Pin functions, parts and IC4 pins from Sega's schematic; filter values from the parts list.[1][2]

Procedure

[edit | edit source]

Open the console

[edit | edit source]
  1. Unplug the adaptor and all leads, and remove any cartridge.
  2. Turn the console over and remove the five Phillips screws around the edge of the bottom case.[5]
  3. Lift the board out of the case and its shielding. Wilson's board was held by five Phillips screws around its edge, two on the voltage regulator and two on each side of the cartridge port.[5]
  4. Find CN2, CN3, the two rows of EMI filters, R5 to R8 and FB1 and FB2 at the front edge of the board on Sega's parts-location drawing.[6]
Sega Master System II controller ports and filters
The controller sockets of a Master System II PAL board, with the orange EMI filters in a row behind each one (EM11 to EM17 visible behind the left-hand socket), bead FB1 and R5 at the left (photo: Evan-Amos, public domain)

Check for a break

[edit | edit source]

With the console unplugged:

  1. Check continuity from each pin of the faulty socket, through its EMI filter, to the IC4 pin in the table. Sega gives this continuity check from the socket terminals to IC4.[3][1]
  2. Where a line has no continuity, check each joint and track along it, and check the filter itself for continuity from its input to its output.[3]
  3. On pins 7 and 9, measure the 330 Ω resistor with one end lifted: 330 Ω.[2][3]
  4. Check pin 5 for continuity to the 5 V rail and pin 8 for continuity to ground through its bead. A pad gets no power if either is open.[1]

Check for a short

[edit | edit source]

If a direction or button is held on by itself:

  1. Measure between each signal pin of the socket and ground (pin 8), and between neighbouring pins. A line that reads short is the stuck one.[3]
  2. Look for solder bridges and damaged tracks between the socket pins and along the lines to IC4; Sega lists a shorted socket, a solder short and a shorted track.[3]
  3. Check the filter on that line for a short from its signal side to ground; replace it if it reads short.[2]
  4. If the line is clean all the way and still pulled low with power on, Sega's last cause is IC4.[3]

Repair

[edit | edit source]
  1. Reflow cracked socket joints; Sega also lists socket pins broken by excessive weight.[3]
  2. Repair a cut track with a wire link along the same path.
  3. Replace a failed EMI filter with the same type as the original: STX222MB in every position except EM17 and EM27, which are STB271KB.[2]
  4. Replace an open 330 Ω resistor.[2]
  5. If the socket itself is cracked or its contacts are damaged, replace it with a nine-pin D-sub of the same footprint. The RGB parts list shows each socket held by two tapping screws, PH 3 × 6 (012-0306), as well as its pins.[2][7]

Reassemble

[edit | edit source]

Refit the board in the bottom case with its screws and shielding, then the bottom case and its five screws.[5]

Testing

[edit | edit source]
  • With a known-good pad in each socket, every direction and both buttons respond in a game.[3]
  • The demonstration screen appears and the game does not start by itself.[3]
  • +5 V between pins 5 and 8 of each socket with the console on.[1]

Revision notes

[edit | edit source]

The circuit and parts are from Sega's documents for the PAL board 171-5922A. The French RGB board, 171-5926A, lists the same resistors R5 to R8, the same filters and the same sockets in angled form.[1][2][7] The Sega Master System (Model 1) has a similar circuit with different designators; see Sega Master System (Model 1) Controller Port Repair. Later Master System II boards are not in the 1991 manual; check the positions on your own board.

[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Sega Enterprises, Ltd., Sega Master System II Service Manual, April 1991, schematic diagram for the PAL version, "IC BD M4JR PAL" 171-5922A, sheet 2 (p. 12, PDF p. 19): CN2 and CN3 (connector D9), pins 1 UP, 2 DW, 3 LE, 4 RI, 5 Vcc, 6 TL, 7 TH, 8 ground, 9 TR; EMI filters EM11 to EM18 (CN2) and EM21 to EM28 (CN3); 330 Ω resistors R5 (CN2 pin 7), R6 (CN2 pin 9), R7 (CN3 pin 7) and R8 (CN3 pin 9); beads FB1 (CN2 pin 8) and FB2 (CN3 pin 8), FBA04; decoupling capacitors CP2 and CP3, 0.022 µF; player 1 lines to IC4 pins 10 (1UP), 11 (1DW), 12 (1LE), 13 (1RI), 14 (1TL), 20 (1TR) and 21 (1TH); player 2 lines to IC4 pins 15 (2UP), 16 (2DW), 17 (2LE), 18 (2RI), 19 (2TL), 22 (2TR) and 23 (2TH). Hosted on this wiki as File:Sega Master System II Service Manual April 1991.pdf.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Sega Enterprises, Sega Master System II Service Manual, April 1991, parts list for the PAL version (pp. 19 to 21, PDF pp. 13 to 15): CN2 and CN3 209-5017 nine-pin D-sub connectors; IC4 315-5237 gate array µPD65005C-114; R5 to R8 479-0331 330 Ω 1/6 W; EM11 to EM16, EM18, EM21 to EM26 and EM28 271-0007 EMI filters STX222MB; EM17 and EM27 271-0006 EMI filters STB271KB; FB1 to FB6 271-0005-1 bead inductors FBA04; CP1 to CP13 151-0170 0.022 µF.
  3. ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Sega Enterprises, Sega Master System II Service Manual, April 1991, repair procedures, p. 8 (PDF p. 10), "In event controls do not respond normally": for a game that does not start, a button that does not respond or no response at all, CON2 or CON3 faulty (disconnection), soldering, cut track, IC faulty, EMI filter faulty, 330 Ω resistor faulty, and a continuity check between the CON2 and CON3 terminals and the terminals of IC4; for a demonstration screen that does not appear, a switch that stays pressed, a direction stuck on, or a game that starts by itself, CON2 or CON3 short-circuited, solder short, shorted track, IC4 faulty. Connector check (p. 5, PDF p. 7): connector pins broken from excessive weight, soldering, cut track, dirty terminals, with controls that do not respond among the symptoms. Symptoms by fault (p. 6, PDF p. 8): a faulty IC4 can stop the controller and pause responding properly.
  4. ↑ Sega Enterprises, Sega Master System II Service Manual, April 1991, p. 10 (PDF p. 12), "Controller related, control pads": controller does not operate, does not move as it should, game does not start (cable cut, faulty connection at connector, cut track, faulty conductive rubber, soldering); moves by itself, switch stays pressed in one direction (cable shorted, solder greasy, conductive rubber stuck).
  5. ↑ 5.0 5.1 5.2 5.3 Adam Wilson, "1992 SEGA Master System II Restoration & Modification", Adam's Vintage Computer Restorations, 13 February 2024: the bottom case is held by five Phillips screws around its edge (the sentence begins "The Game Gear is easy to dismantle", evidently a slip in an article about the Master System II); the main board is held into the bottom case and the RF shielding by five Phillips screws around its edge, two on the voltage regulator and two on each side of the cartridge port.
  6. ↑ Sega Enterprises, Sega Master System II Service Manual, April 1991, parts location drawing "IC BD M4JR PAL-G" 837-7367 (p. 15, PDF p. 22), with sister drawings for the other regional boards on PDF pp. 21 to 26. Hosted on this wiki as File:Sega Master System II M4 Jr PAL-G parts location.png.
  7. ↑ 7.0 7.1 Sega Enterprises, Sega Master System II Service Manual, April 1991, parts list for the RGB version (pp. 25 and 26, PDF pp. 16 and 17), PCB 171-5926A: CN2 and CN3 209-5017-01 D-sub 9P angle type; CN2L, CN2R, CN3L and CN3R 012-0306 tapping screw PH 3 × 6; R5 to R8 330 Ω; EM11 to EM18 and EM21 to EM28 EMI filters, EM17 and EM27 STB271KB.
Retrieved from "https://retrotechwiki.com/index.php?title=Sega_Master_System_II_Controller_Port_Repair&oldid=30369"