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Atari 2600 Controller Port Repair

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Atari 2600 six-switch motherboard controller ports and J201
The controller ports J202 and J203 on a six-switch motherboard, with the small disc capacitors on their lines beside them (photo: Evan-Amos, public domain)

The two controller ports of the Atari 2600 are nine-pin connectors soldered to the board: J202 for the left player and J203 for the right.[1] Pins 1 to 4 carry the joystick directions to the 6532 (A202), pin 6 carries the fire button, pins 5 and 9 carry the paddles to the TIA, pin 7 is +5 V and pin 8 is ground.[2] Atari's tech tip 9 asks for every port to be checked for pushed-back or broken pins, and Best Electronics notes that one bad pin is enough to stop a joystick or paddle working.[3][4]

The steps apply to the six-switch CX2600 and the four-switch CX2600A in Atari's field service manual. On the CX2600, Atari's tech tip 12 checks the 4050 buffer first for any trigger fault; see Atari 2600 Static Protection Modification.[3]

Symptoms

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  • A direction or the fire button does not work with a known-good joystick. Best Electronics tests with Missile Command in the left port, checking all eight directions and the button; Atari's own joystick check uses Combat.[4][5]
  • The fault follows the port, not the joystick: it stays in one port with two different joysticks. Best Electronics points out that the chance of two unknown joysticks having the same fault is slight.[4]
  • Erratic paddles. Atari's checklist names the TIA, the paddle timing capacitors and the ports.[6]

If the ports look good and a known-good joystick still fails, Best Electronics suspects the 6532 (C010750).[4]

Tools and parts

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  • A known-good joystick and paddles, a multimeter and an oscilloscope for the paddle lines.[7]
  • Replacement port: Atari part C010448, or C010727 as the alternative, at J202 and J203 on both boards.[8]
  • Atari's blue shorting plugs (MA017602, ordered in pairs) and the Diagnostic Test Cartridge, if you have them.[9]
Joystick lines: port pin, 6532 pin and capacitor (Atari pp. 4-26, 6-22)
Port pin 6532 (A202) pin Capacitor, CX2600 Capacitor, CX2600A
J202 pin 4 15 C235 C230
J202 pin 3 14 C234 C229
J202 pin 2 13 C233 C228
J202 pin 1 12 C232 C227
J203 pin 4 11 C231 C226
J203 pin 3 10 C230 C225
J203 pin 2 9 C229 C224
J203 pin 1 8 C228 C223

The pin and capacitor numbers are from the connection charts in Atari's I/O line procedures.[10][11]

Procedure

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Inspecting the ports

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  1. Look into each port with a light. There should be two rows of pins, five and four. Look for bent, missing, broken or pushed-in pins.[4]
  2. Replace any port with a pushed-back or broken pin (tech tip 9).[3]

Tracing a dead joystick line

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Atari CX-2600A schematic, controller ports and 6532
The controller jacks on Atari's CX-2600A schematic: pins 1 to 4 to the 6532's port A, pin 6 (trigger) with its pull-up and filter, pin 7 at +5 V and pin 8 at ground

Atari's procedure, the same on both boards apart from the capacitor numbers:[10][11]

  1. Find which lines are faulty, from the test cartridge's matrix screen or by testing each direction.
  2. With the joystick unplugged, measure +5 V on each faulty line at the port (table above).
  3. If +5 V is present, swap the 6532 (A202), then the 6507 (A200), then the TIA (A201). If the fault remains, look for the line shorted to +5 V.
  4. If +5 V is missing at the port, measure the 6532 pin. If it is present there, repair the open track between the 6532 pin and the port.
  5. If it is missing at the 6532 pin too, check the track from that pin for a short to ground and repair it.
  6. If there is no short, swap the 6532. If +5 V is still missing at the 6532 pin, replace the capacitor on that line.
  7. If the line is now right but the fault remains, swap A200, then A201.

Fire button lines

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On the CX2600 the triggers pass through the 4050 buffer at A203 and the zener and capacitor pairs C236/CR202 and C237/CR203. Follow the trigger line checks in Atari 2600 Static Protection Modification#Checking the trigger lines.[1] On the CX2600A each trigger line goes from pin 6 of the port through a 220 Ω resistor to the TIA, with a 10 kΩ pull-up to +5 V and a 470 pF capacitor to ground; Atari's checklist names only the ports and the controller for a dead fire button on that board.[2][6]

Paddle lines

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Paddle connections (Atari pp. 4-34, 6-29)
Player TIA (A201) pin Port pin Capacitor (CX2600)
1 40 J202 pin 5 C215
2 39 J202 pin 9 C216
3 38 J203 pin 5 C217
4 37 J203 pin 9 C218

Atari's paddle lines test, with the shorting plugs fitted and the test cartridge in its matrix mode:[12][13]

  1. Look for the RC waveform of Atari's figure 4-10 at each port pin in the table.
  2. If it is present at the port, look for it at the TIA pin. If it is missing there, repair the open track between the TIA and the port; if it is present, swap A201, then A200, then A202.
  3. If it is missing at the port, check continuity from the port pin to the TIA pin, and look for open tracks and resistors.
  4. If there is continuity, replace the paddle capacitor on that line, then check for the waveform again.
  5. If it is still missing, swap A201, A200 and A202 in turn; if that fails, the paddle line is open or shorted.

Atari's chart for the CX2600A prints the same capacitor numbers, C215 to C218, as the CX2600 chart, but the CX2600A parts list and checklist put the 0.068 µF paddle capacitors at C218 to C221.[13][8][6] Identify them on the board by value.

Replacing a port

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  1. Open the console and lift out the board as in Atari 2600 Power Supply Circuit Repair#Opening the console. On the six-switch console, take the motherboard out of its metal case.[14][15]
  2. Desolder the faulty port and fit the replacement (Atari C010448 or C010727) in the same position.[8]
  3. Repeat the +5 V check on each joystick line at the new port before reassembly.[10]
  4. On a six-switch console, refit the dust cover for the joystick and power ports when the board goes back.[15]

Testing

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  • Run Atari's diagnostic matrix test: with the left difficulty switch at B, the matrix changes when the shorting plugs are fitted.[16]
  • Without the test cartridge, check all eight directions and the fire button in each port with a known-good joystick, as Best Electronics does with Missile Command, and check paddles in a paddle game.[4]
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References

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  1. ↑ 1.0 1.1 Atari, Field Service Manual FD100133 Rev. 02, "Trigger Line Troubleshooting Procedure", p. 4-27: J202 (left trigger) and J203 (right trigger), pin 6.
  2. ↑ 2.0 2.1 Atari, Inc., Video Computer System (Main Board) schematic, CX-2600A, sheet 2 of 4, 30 May 1982: the controller jacks, their wiring to the 6532 and TIA, the trigger pull-ups and filters, +5 V on pin 7 and ground on pin 8. Hosted as File:Schematic Atari2600A 2000.png.
  3. ↑ 3.0 3.1 3.2 Atari, Field Service Manual FD100133 Rev. 02, NTSC technical tips at the back of the manual: tip 9 (nine-pin connectors) and tip 12 (the 4050 and trigger faults), pp. 7-2 and 7-3.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Best Electronics, "What to look for when buying a used or third party reconditioned Atari 2600 / 2600A / 2600Jr console", tip 8: the nine-pin ports, the test with known-good joysticks, and the 6532 (C010750) when the ports are good.
  5. ↑ Atari, Field Service Manual FD100133 Rev. 02, Section 7, "Joystick (X-Y) Controller Check".
  6. ↑ 6.0 6.1 6.2 Atari, Field Service Manual FD100133 Rev. 02, Section 5 symptom checklists, controller failures, pp. 5-4 and 5-7.
  7. ↑ Atari, Inc., Video Computer System Field Service Manual, Domestic Model 2600/2600A, FD100133 Rev. 02, "Equipment Requirements", p. 3-1. Hosted as File:Atari 2600 and 2600A Field Service Manual.pdf; see Atari 2600 and 2600A Field Service Manual.
  8. ↑ 8.0 8.1 8.2 Atari, Field Service Manual FD100133 Rev. 02, Section 8 parts lists, pp. 8-2 and 8-6 to 8-7: controller sockets C010448 and C010727 at J202 and J203; epoxy-dipped 0.068 µF capacitors at C215 to C218 (CX2600) and C218 to C221 (CX2600A).
  9. ↑ Atari, Tech Tip 1, 23 April 1982, "Part Numbers, Diagnostic Tools": MA017600, MA017601 and MA017602. In Atari 2600 and Atari 5200 Field Change Orders, Upgrade Bulletins, Tech Tips, hosted as File:Atari 2600 and 5200 Field Change Orders and Tech Tips.pdf.
  10. ↑ 10.0 10.1 10.2 Atari, Field Service Manual FD100133 Rev. 02, "Defective I/O Lines Troubleshooting Procedure", p. 4-26, with its chart of A202 lines, capacitors and connector pins.
  11. ↑ 11.0 11.1 Atari, Field Service Manual FD100133 Rev. 02, "2600A Defective I/O Lines Troubleshooting Procedure", p. 6-22.
  12. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Paddle Lines Test", p. 4-34, with its connection chart.
  13. ↑ 13.0 13.1 Atari, Field Service Manual FD100133 Rev. 02, "2600A Paddle Lines Test", p. 6-29, with its connection chart.
  14. ↑ Vintage Gaming and More, "Atari 2600 4 Switch Tune Up Kit Installation Guide": opening the four-switch console.
  15. ↑ 15.0 15.1 Vintage Gaming and More, "Atari 2600 6 Switch Tune Up Kit Installation Guide": opening the six-switch console, the dust cover for the joystick and power ports, and reassembly.
  16. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Diagnostic Matrix Test", p. 3-11.


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