Atari 2600 Console Switch Repair

The power switch S201 and the TV-type switch S204 on a four-switch board, foam covers removed (photo: Vintage Gaming and More)

The console switches on the Atari 2600 are metal-cased slide switches soldered to the board. On the six-switch CX2600 they sit on the separate switchboard; on the four-switch CX2600A the power, TV-type, game select and game reset switches are at the front of the single board and the difficulty and channel switches are at the rear. Best Electronics finds that they wear out, most often the power and reset switches, and Dave Farquhar finds them prone to dirt and oxidation. The five game switches each drive an input of the 6532 (A202), so a switch fault can be traced with a meter from the switch to the chip.

Console switches and the 6532 pins they drive

Function	CX2600	CX2600 J101/J201 pin	6532 (A202) pin
Power	S101	2 (unregulated in)	None
TV type (colour or black and white)	S102	4	21
Left difficulty	S103	5	17
Right difficulty	S104	7	16
Game reset	S105	8	24
Game select	S106	9	23

The CX2600 designators and J101 pins are from Atari's channel 3 switchboard schematic and the 6532 pins from the connection charts in Atari's switch flowcharts; the same 6532 pins are used on the CX2600A. On the CX2600A the power switch is S201 and the other two-position front switch, TV type, is S204; the spring-return select and reset switches are S202 and S203, and the PCB slide switches at the rear are S200, S205 and S206.

Symptoms

Best Electronics' tests need only a game and a television:

• With the power switch on, push the top of its lever slightly left and right. If the game glitches, resets or the picture goes off, the switch is bad.
• Slide the select and reset levers up and down. They should move smoothly without binding. Heavy interference on the screen as they move, or no response from the game, means the switch needs replacing.
• Check the TV-type switch on a colour television.
• Test the difficulty switches with a two-player game of Space Invaders, Breakout or Super Breakout: the player's cannon or paddle changes size as the switch moves. Repeat for each player.
• Black or white corrosion on the brushed aluminium levers marks a console that has had very heavy use.

Atari's symptom checklist puts "switches not working" down to the 6532 (A202), the capacitors on its switch lines and the switches themselves: C222 to C227 and S102 to S106 or J101 on the CX2600, and S202 to S206 on the CX2600A. A console that will not power on at all is covered in Atari 2600 Power Supply Circuit Repair.

Tools and parts

• A multimeter, a soldering iron and solder, a desoldering tool, needle-nose pliers, a small flat-blade screwdriver, cotton buds and isopropyl alcohol.
• Plastic-safe electronics cleaner. Farquhar uses CRC QD contact cleaner.
• Replacement switches, if a switch cannot be repaired. Atari's numbers: CX2600 S101 to S104 slide switches C010373 or C019025, S105 and S106 spring-return C010388 or C019026, S107 C012241 or C012242; CX2600A S201 and S204 C010373, S202 and S203 C010388, S200, S205 and S206 C012241 or C017549. Best Electronics sells replacements; Farquhar notes they tend to be expensive.

Procedure

Opening the console

Remove the screws and lift out the board as described in Atari 2600 Power Supply Circuit Repair#Opening the console: four screws on the four-switch console, eight on the six-switch, where the switchboard is then unplugged and unscrewed from the motherboard's case. Take the black foam dust covers off the switches and keep them.

Finding the faulty switch with a meter

Each console switch on the CX2600 switchboard connects one J101 line to ground (field service manual figure 2-4)

With a switch open its line sits at +5 V, and closing the switch takes it to ground. Atari's flowcharts check the voltage at the 6532 end of the line with the switch open and then closed.

CX2600A:

1. Power the board and set the faulty switch to its open position. Measure the 6532 pin for that switch (table above). It should read +5 V.
2. If it does not, check whether the switch is shorted internally and replace it if it is. Otherwise check whether the capacitor on that line is shorted to ground and replace it if it is.
3. If the switch and capacitor are good and the 6532 pin still has no +5 V, swap the 6532 (A202), then the 6507 (A200), then the TIA (A201). If the pin has +5 V but the switch end does not, the track between them is open; repair it.
4. With +5 V present, close the switch and measure the 6532 pin again. It should read 0 V.
5. If it does not, check for an open track between the 6532 and the switch, then check that the other side of the switch is connected to ground. Repair an open track; replace the switch if its ground side is connected.
6. If the pin does go to 0 V and the game still ignores the switch, swap A202, A200 and A201 in turn.

CX2600, switchboard side:

1. Set the faulty switch to its open (up) position and measure the J101 pin for that switch. It should read +5 V.
2. If it does not, check that line for a short to ground and repair it. If there is no short, check continuity through the 12-way connector and change J201 if it is open.
3. Close the switch (down). The J101 pin should read 0 V.
4. If it does not, check that one side of the switch is tied to ground as the schematic shows. If it is, replace the switch; if it is not, repair the open between the switch and ground.

CX2600, motherboard side:

1. With the switch open, measure +5 V at the J201 pin for that switch. If it is missing, measure the 6532 pin; if that has no +5 V either, look for a shorted track, then swap A202, then check whether the capacitor on that 6532 line is shorted to ground, then swap A200 and A201.
2. Close the switch. The 6532 pin should read 0 V. If it does not, look for an open track between J201 and the 6532.
3. If the voltages are right and the switch still has no effect, swap A202, A200 and A201 in turn.

Cleaning a switch in place

Switches with openings in the top and bottom of the case can be cleaned without removing them; fully closed switches have to come out.

1. With the power off, work the switch back and forth many times. Farquhar works a power switch about 100 times before using cleaner.
2. Spray electronics cleaner into the opening in the side of the switch, or apply isopropyl alcohol with a cotton bud on both sides of the slider.
3. Work the switch 15 to 20 times while it is wet.
4. Let it dry for 30 minutes before powering the console.

Vintage Gaming and More finds that electronics cleaner fixes about nine switches in ten.

Checking the solder joints and the switch

1. Turn the board over and look at the switch's solder joints. Reflow any that are cracked or loose.
2. Four of each switch's six pins are joined together by the board. Check continuity between that group of four and the remaining pair while moving the switch: there should be continuity in one position.
3. If there is none, desolder the switch and test each contact with the meter.
4. A two-position slide switch that works in one direction only can be turned round and soldered back, so that its good side carries the circuit.

Dismantling and cleaning a switch

Bending the case tabs to release the contact base (photo: Vintage Gaming and More)

A slide switch in pieces: contact base, lever and slider, two contact springs, case (photo: Vintage Gaming and More)

A spring-return select or reset switch in pieces, with its return spring (photo: Vintage Gaming and More)

Vintage Gaming and More's procedure, for a switch already out of the board. The spring-return select and reset switches are harder to reassemble than the plain slide switches.

1. Bend the metal case tabs inwards with needle-nose pliers and lift the contact base out. Keep every part; the select and reset switches have a spring.
2. Clean the two moving contacts and the ends of the six fixed contacts with a cotton bud and isopropyl alcohol.
3. Bend the moving contacts slightly wider so that they press harder on the fixed contacts.
4. Put the contacts back in the slider. On a spring-return switch, one side of the centre slot is open and the other closed; fit the spring so that it rests on the closed side, and use the metal tab on the bottom piece to load the spring.
5. Fit the base and bend the case tabs back to hold it closed. A small screwdriver separates the two small prongs before the pliers bend them in.
6. Check continuity again before soldering the switch back.

On a CX2600 channel 2-3 switchboard, the holes for the game reset and game select switches may be too close for the switch legs; Atari bends the legs inwards to fit them.

Reassembly

1. Make sure each CX2600 switch sits flat and square to the switchboard. Atari's tech tip 14 resets any crooked switch.
2. Refit the static strips if the console has them. Atari fitted them to the CX2600 switchboard and to the front-panel switches of CX2600A boards of revisions 1 to 13; see Atari 2600 Static Protection Modification.
3. Refit the black foam dust cover on every switch. Best Electronics treats a 2600 or 2600A whose switches have no foam covers as one that has been opened.
4. Reassemble the console in the reverse order of opening it.

Testing

• Atari's diagnostic matrix test, run from the Diagnostic Test Cartridge with the left difficulty switch at B, blacks out an area of the on-screen matrix while game select or game reset is held down.
• Without the test cartridge, repeat Best Electronics' tests: the difficulty switches change the cannon or paddle size in Space Invaders, Breakout or Super Breakout, the TV-type switch changes the picture on a colour set, and select and reset act on the game.
• Measure the 6532 pin for each repaired switch: +5 V open and 0 V closed.

Related pages

• Atari 2600
• Atari 2600 Troubleshooting Guide
• Atari 2600 General Maintenance
• Atari 2600 Power Supply Circuit Repair
• Atari 2600 Static Protection Modification
• Atari 2600 and 2600A Field Service Manual