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Atari 5200 Controller Flex Circuit and Potentiometer Repair

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Atari-5200-Controller
The CX52 controller supplied with the Atari 5200 (photo: Evan-Amos, public domain)

The CX52 controller of the Atari 5200 (Atari assembly CA018107, used with every 5200 model) reads its keypad, four fire buttons and three select buttons through a flex circuit, and its joystick through two potentiometers in the bottom case that are moved by two actuator plates in the top case.[1][2] The flex circuit and the pots are the parts that fail: iFixit's flex board guide calls faulty controller wiring, with buttons that stop responding, one of the most common 5200 problems.[3] Atari's field service manual gives a test without a console, a continuity table for the cable and flex circuit, a pot alignment procedure and the disassembly order, and three Atari tech tips cover the boot, the knob puller and a firmer fire button.[4][5][6][7][8][9]

Atari CX52 controller exploded view (FSM figure 6-1)
Atari's exploded view of the CX52: keypad, function key pad, flex circuit pad and flex circuit above, fire buttons at the sides, and the two pots in the bottom case (field service manual figure 6-1)

Symptoms

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  • One keypad key does nothing: Atari's first step is to clean the 12-key switch set, then to replace the flex circuit pad.[10]
  • Several keys, the joystick or the fire buttons fail: Atari checks the cable first (Table 6-1 below), then replaces the flex circuit pad or aligns or replaces the pots.[10]
  • The joystick reads at the extremes or jumps: with the Diagnostic Cartridge 1.1 on the Pokey Adjust screen, a good controller in port 1 reads less than 25 at position 1 and more than 190 at position 2, and the reading changes evenly in between.[11]

Try the controller in another port and another controller in the same port. A fault that stays with the port is in the console: Atari's trigger, soft-fire, keyboard and pot-line charts are summarised on the Atari 5200 Troubleshooting Guide.[11]

Tools and parts

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  • An ohmmeter, a Phillips screwdriver for the three case screws, and a flat-blade screwdriver for the select switch bezel.[4][12][3]
  • Atari's controller knob puller, FC100214, or another tool that does the same job.[8]
  • For the console test: a known-good 5200 and controller, a colour television and the Diagnostic Cartridge 1.1.[11]

Atari's part numbers for the CX52 (all models):[2]

CX52 controller parts
Part Atari number
Flex circuit C018124
Flex circuit and key pad assembly CA018989
12-key switch set C018126
Auxiliary function keys C018128
Fire button switch set (two buttons); Tech Tip 10's firmer button C020501
Top and bottom actuator plates C018112, C018113
Slide block C018114
Boot and retaining ring C018115, C018116
Pivot shaft and knob C018120, C018121
Pot and arm assembly CA018987
Cable pot assembly CA018988
Controller cable assembly CA018145
Top housing assembly CA018223

Procedure

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Testing without a console

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Atari CX52 controller joystick positions 1 and 2 (FSM figure 6-2)
Joystick positions 1 and 2 used in the pot tests (field service manual figure 6-2)
Atari CX52 controller cable connector pins (FSM figure 6-3)
Pin numbers of the 15-pin controller plug (field service manual figure 6-3)

Measure through the cable at the 15-pin plug.[4]

  1. Move the joystick to position 1, towards the upper left in Atari's figure 6-2. Measure between pins 11 and 9, and between pins 10 and 9. Each reading should be no more than 50 kΩ.
  2. Move the joystick to position 2, towards the lower right. Each reading should now be at least 430 kΩ higher than at position 1.
  3. Check each button between the pins below. Released, the meter should read open circuit; pressed, less than 50 kΩ. Press the left and right fire buttons separately.
Button test pins (FSM p. 6-5)
Button Pins Button Pins
Top fire 15 and 14 Bottom fire 15 and 13
START 4 and 7 PAUSE 4 and 6
RESET 4 and 5 1 7 and 3
2 7 and 2 3 7 and 1
4 6 and 3 5 6 and 2
6 6 and 1 7 5 and 3
8 5 and 2 9 5 and 1
* 8 and 3 0 8 and 2
# 8 and 1

Checking the cable

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For each failed key, check continuity from the cable plug pin to the flex circuit pad pin given in Atari's Table 6-1. The flex circuit pad pins are numbered 11 (left) to 1 (right) with the controller held in the normal playing position. Each key appears on two lines, one for its column and one for its row.[10][5]

Game controller continuity check (FSM Table 6-1, p. 6-7)
Failed key Cable plug pin Flex circuit pad pin
1, 4, 7, * 3 8
2, 5, 8, 0 2 7
3, 6, 9, # 1 6
1, 2, 3, START 7 9
4, 5, 6, PAUSE 6 5
7, 8, 9, RESET 5 4
*, 0, # 8 3
START, PAUSE, RESET 4 10
Top (soft) fire, "not presently used in games" 15; 14 1; 11
Bottom fire (trigger) 13; 14 2; 11
Horizontal (pot 2) 10 and 9 (pot)
Vertical (pot 1) 11 and 9 (pot)
Atari CX52 controller schematic (FSM figure 6-9)
The CX52 schematic: keypad matrix S1 to S12, START, PAUSE and RESET (S13 to S15), top fire (S16, S17), bottom fire (S18, S19), the two pots and the cable colours to plug P1 (field service manual figure 6-9)

Atari's schematic gives the cable colours: pin 15 orange (ground), pin 14 white and green (soft fire), pin 13 yellow (trigger), pin 10 brown (pot 2), pin 11 red (pot 1) and pin 9 black (+CAV).[13] The table prints pin 14 on both fire-button lines, where the button test and the schematic pair the bottom button with pins 15 and 13.[4][5][13]

Disassembly

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Atari CX52 controller select switch bezel removal (FSM figure 6-6)
Prising out the select switch bezel (field service manual figure 6-6)

Atari's order:[12]

  1. Slide a flat-blade screwdriver under the select switch bezel, between the switches, and prise the bezel out. Remove the select switches.
  2. Remove the three screws from the bottom case.
  3. Separate the top case from the bottom case. The flex circuit and keypad can now be lifted out. iFixit's guide advises moving the joystick as little as possible while the case is apart, to keep the arms lined up with the pots.[3]
  4. Pull the two fire buttons on each side upwards.

The flex circuit pad and the pots can now be checked or replaced.[12]

Cleaning the keypad or replacing the flex circuit

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  1. If one key failed, look for contamination on the 12-key switch set and clean it.[10]
  2. If the switch set is clean, or several keys failed and the cable passed Table 6-1, replace the flex circuit pad.[10]
  3. iFixit's guide frees the strip that runs to the START, PAUSE and RESET buttons, peels the old flex circuit away, disconnects it from the cable connector, then fixes the new one where the old one was held and reconnects it.[3]

Aligning or replacing the pots

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Atari CX52 controller pot and arm assembly (FSM figure 6-4)
Pot and arm: terminals 1 to 3 and arm positions A and B (field service manual figure 6-4)
Atari CX52 controller top, underside (FSM figure 6-5)
Underside of the top case: actuator plates, slide block and the openings for the two pot arms (field service manual figure 6-5)

Atari's alignment procedure, after the cable has passed Table 6-1. Atari says the pots must be aligned whenever they are replaced.[10][6]

  1. With the controller apart, remove the arm from the pot's wiper shaft.
  2. Turn the wiper shaft until the reading between terminals 2 and 3 is 5 to 20 kΩ.
  3. Refit the arm on the wiper shaft in position A of figure 6-4.
  4. Reassemble the controller (below).
  5. Repeat the two joystick readings from the test without a console: no more than 50 kΩ at position 1, and at least 430 kΩ more at position 2.
  6. If the test still fails, replace the pots if they have not been replaced already. If they have, replace the actuator plates, which Atari supplies as a set with the slide block.

Replacing a damaged boot

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Atari's Tech Tip VCS 8:[7]

  1. Dismantle the controller as above, remove the top case and pull off the joystick handle.
  2. Remove the boot retaining ring, then remove and discard the damaged boot.
  3. If the top case has a square ridge around the access well, replace the top case with the later one that has no ridge.
  4. Fit the new boot, the retaining ring and the joystick handle, and reassemble.

Removing the joystick knob

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Atari CX52 controller knob removal (FSM figure 6-7)
Levering the knob off with the puller (field service manual figure 6-7)

Atari's method with the knob puller FC100214, from the manual and Tech Tip 9:[12][8]

  1. Push the knob shaft into one corner of the opening in the top housing.
  2. Push the boot down with the tool to expose the shaft.
  3. Push the tool towards the shaft until the shaft sits in the notch in the tool's head.
  4. Lever the tool gently and the knob pops off. Atari notes that the boot is not damaged if this is done with care.
  5. Note the positions of the actuator plates and slide block before removing them.

Reassembly

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Atari CX52 controller pot arm positions for assembly (FSM figure 6-8)
Pot arm positions in the bottom case for assembly (field service manual figure 6-8)

Atari's order:[14]

  1. Place the boot on the outside of the top case.
  2. Place the actuator plates and slide block in the underside of the top case.
  3. From underneath, pass the pivot shaft through the holes in the slide block and boot.
  4. From the top, push the joystick onto the pivot shaft.
  5. Refit the fire buttons and place the keypad on the support plate.
  6. Set the pot arms as shown in figure 6-8.
  7. Pass the select switches' flex strip through the opening at the left of its well.
  8. Fit the top case onto the bottom case. Check that the actuator plates sit correctly in the top case, that the pot arms engage the holes in the actuator plates, and that the joystick pivot shaft sits in the well between the two pots.
  9. Refit and tighten the three screws.
  10. Place the select switches on the function key pad and press the bezel into place over them.

Testing

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With a known-good console, a colour television and the Diagnostic Cartridge 1.1:[11]

  1. Fit a known-good controller in port 1, press 5 and then START to bring up the Pokey Adjust screen, then swap in the repaired controller.
  2. At joystick position 1 the port 1 horizontal and vertical readings should be less than 25; at position 2, more than 190. Moving the stick slowly between the two should change the readings evenly, without sudden jumps.
  3. Press each key. The KB-1 column should show C, D and E for START, PAUSE and SELECT, the digits for 1 to 9 and 0, A for * and B for #.
  4. Press one bottom fire button: the menu replaces the Pokey Adjust screen. Return to Pokey Adjust and repeat with the other bottom button.
  5. Check the top fire buttons with the meter (pins 15 and 14).

Tech Tip 10 introduced a firmer fire button, C020501, after the original was described as "mushy and slow to respond"; Atari says it makes no difference to testing.[9]

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References

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  1. ↑ Atari, Inc., CX5200 Field Service Manual, FD100127 Rev. 4, July 1983, section 6, pp. 6-1 and 6-2: the controller's parts, figure 6-1. Hosted here as Atari CX5200 Field Service Manual.
  2. ↑ 2.0 2.1 Atari, CX5200 Field Service Manual FD100127 Rev. 4, section 8, parts list: "Atari CX52 controller assy (all models)", pp. 8-10 and 8-11, and the major assemblies, p. 8-1.
  3. ↑ 3.0 3.1 3.2 3.3 iFixit, "Atari 5200 Controller Flex Board Replacement", last updated 19 February 2016 (CC BY-NC-SA; cited, not copied).
  4. ↑ 4.0 4.1 4.2 4.3 Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Controller testing without a 5200 console", p. 6-5: pot readings through the cable and the button pin pairs.
  5. ↑ 5.0 5.1 5.2 Atari, CX5200 Field Service Manual FD100127 Rev. 4, Table 6-1, "Game Controller Continuity Check", p. 6-7.
  6. ↑ 6.0 6.1 Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Pot arm alignment procedure", pp. 6-8 and 6-9, figures 6-4 and 6-5.
  7. ↑ 7.0 7.1 Atari, Inc., Tech Tip VCS 8, "CX5200 Controller" (damaged boots), in Atari 2600 and Atari 5200 Field Change Orders, Upgrade Bulletins, Tech Tips. Hosted here as Atari 2600 and 5200 Field Change Orders and Tech Tips.
  8. ↑ 8.0 8.1 8.2 Atari, Inc., Tech Tip VCS 9, "5200 Controller Knob Puller Tool", April 1983, in Atari 2600 and Atari 5200 Field Change Orders, Upgrade Bulletins, Tech Tips. Hosted here as Atari 2600 and 5200 Field Change Orders and Tech Tips.
  9. ↑ 9.0 9.1 Atari, Inc., Tech Tip VCS 10, "New Fire Button (C020501)", 8 April 1983, in Atari 2600 and Atari 5200 Field Change Orders, Upgrade Bulletins, Tech Tips. Hosted here as Atari 2600 and 5200 Field Change Orders and Tech Tips.
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Failures", p. 6-6, and figure 6-3 (cable connector pins).
  11. ↑ 11.0 11.1 11.2 11.3 Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Controller testing using the 5200 console", pp. 6-3 and 6-4: figure 6-2, Pokey Adjust readings, the KB-1 column and the bottom fire buttons.
  12. ↑ 12.0 12.1 12.2 12.3 Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Controller disassembly/assembly", pp. 6-10 and 6-11, figures 6-6 and 6-7.
  13. ↑ 13.0 13.1 Atari, CX5200 Field Service Manual FD100127 Rev. 4, figure 6-9, "CX52 Game Controller Schematic", p. 6-13.
  14. ↑ Atari, CX5200 Field Service Manual FD100127 Rev. 4, "Assembly", pp. 6-11 and 6-12, figure 6-8.


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