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Atari 2600 Power Supply Circuit Repair

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Atari 2600 CX2600A regulator A203 area (Rev 16)
The regulator A203 (a 78M05) on a Rev 16 four-switch board, screwed to its tinned heatsink pad; the large axial electrolytic above it is the 2200 µF reservoir (photo: Evan-Amos, public domain)

The Atari 2600 takes unregulated DC from an external adaptor, which Atari calls the battery eliminator, and makes its own +5 V with a 78M05 regulator (Atari part C014348) inside the console.[1] When that supply path fails the console shows snow or nothing at all, or the picture drops out when the plug or the power switch is moved. Dave Farquhar lists the usual causes of a 2600 that will not power on as a bad adaptor, a dirty power switch, a loose power jack and a failed regulator.[2] The steps below follow Atari's field service flowcharts through the supply path on both versions of the console that Atari's manual covers: the six-switch CX2600 and the four-switch CX2600A, every board revision.[3][4] The Atari 2600 Jr has a different board.

The two versions route power differently:[5][6][7]

Power path on each board
Stage CX2600 (six switches, two boards) CX2600A (four switches, one board)
Power input jack J204, on the motherboard J201, 3.5 mm, tip positive
Link between boards 12-way cable: unregulated supply out on J201 pin 2 of the motherboard to J101 pin 2 of the switchboard, +5 V back on pin 1 None
Reservoir capacitor C106, 2200 µF 16 V, switchboard C243, 2200 µF 16 V
Power switch S101, switchboard S201
Regulator A101, 78M05, switchboard A203, 78M05

Symptoms

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  • A snowy screen with no modulation at all. Atari's procedure for this symptom starts with the connections to the television and a known-good battery eliminator, then measures the supply.[8]
  • The picture goes off when the power plug is moved gently in a small circle while a game is running. Atari's tech tip 8 replaces the jack.[9] Best Electronics adds that a broken wire inside the adaptor's lead, near the plug or where it enters the adaptor, gives the same symptom.[10]
  • The game glitches, resets or the picture disappears when the top of the power switch lever is pushed slightly left and right in its on position. Best Electronics treats this as a worn switch.[10]
  • On the CX2600A, lines and bright grid distortion with a loud hum that adjustment will not clear, which may go away for a while after the console has been off, are put down by Atari's February 1982 service bulletin to a leaking C241 or C242 between the power jack and the regulator.[11]

A black or solid-coloured screen has its own flowchart in Atari's manual, which starts from the clock signals; see the Atari 2600 Troubleshooting Guide.[12] Before opening the console, check the channel, the cable connections and another cartridge, as Farquhar advises.[2]

Safety

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The work is all at low voltage; Farquhar expects no more than 15 V DC inside the console.[13] The 2200 µF reservoir sits on the adaptor side of the power switch on both boards.[6][7] Farquhar discharges it by unplugging the adaptor, switching the console on and leaving it for about five minutes, and otherwise keeps his fingers off its leads.[2] The 6507, 6532 and TIA are sensitive to static; Atari asks technicians to wear a grounding strap.[14]

Tools and parts

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  • A multimeter, and a known-good adaptor to test with.[8][2] Farquhar expects a working original adaptor to read more than 9 V across its plug with no load; a newer adaptor may read 9 V.[2]
  • A replacement regulator. Atari fitted a 78M05 in a TO-220 package, part C014348, at A101 (CX2600) and A203 (CX2600A).[1] Farquhar fits a 7805 in its place.[13] Use a new part: retro64 fitted a 7805 taken from a Commodore 64 board to a 2600 Jr and it gave about 6 V on the original Atari adaptor until it was replaced with a new one.[15]
  • Heatsink compound and isopropyl alcohol.[13]
  • A 3.5 mm jack, Atari 79-5918, if the jack has to be replaced. The same part is listed at J204 on the CX2600 and J201 on the CX2600A.[1]
  • A 2200 µF 16 V reservoir (Atari C014373) if C106 or C243 has failed; the values for the other capacitors are on the Atari 2600 Capacitor Replacement Guide.[1]
  • A soldering iron (Farquhar uses a 25 W iron), solder, flux and a desoldering tool.[2][13]

Procedure

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Opening the console

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Four-switch CX2600A:[16][17]

  1. Turn the console over and remove the four screws. The two front screws go in straight; the two rear screws sit at an angle, so hold the screwdriver at the angle of the hole to avoid stripping them.
  2. Separate the case halves, prying gently with a plastic tool if they stick. The board sits in the top half and lifts out.
  3. Unplug the RF cable from the board.
  4. Take the black foam covers off the switches and keep them.

The regulator A203 and the power jack J201 are outside the metal shield, so the shield can stay in place for this repair.[17][18]

Six-switch CX2600:[19][17]

  1. Turn the console over and remove the eight screws: two at the front, four at an angle at the rear and two in the middle that hold the board assembly.
  2. Lift the top case off, then lift out the switchboard and motherboard together. Disconnect the RF cable if it is still attached to the switchboard.
  3. Unplug the 12-way cable and remove the two screws that hold the switchboard to the motherboard's metal case.
  4. Take the foam covers off the switches and keep them.
Atari 2600 six-switch switchboard
A six-switch switchboard: the regulator A101 is on the tinned area at lower left, the axial 2200 µF reservoir C106 lies among the left-hand switches, the 12-pin connector J101 is in the middle and the RF modulator is at the right (photo: Evan-Amos, public domain)

Following the supply on a CX2600A

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Atari CX-2600A schematic, power input and regulator
Power input on Atari's CX-2600A schematic: the jack, the 0.1 µF and 2200 µF capacitors ahead of the power switch, the 7805 and the +5 V feeds
Atari 2600 and 2600A IC pinouts (FSM figure 2-1)
Atari's pinout for the regulator: in, ground, out, seen from the front with the tab at the top (field service manual figure 2-1)

Atari's flowchart for a snowy 2600A works back from the regulator output.[4] The regulator pins are in, ground and out, reading from the left with the printed face towards you and the tab at the top.[20]

  1. Plug in a known-good adaptor and switch on. Put the meter's black lead on the regulator's fixing screw, which is grounded. Farquhar uses the screw instead of the centre pin to avoid shorting anything.[2]
  2. Measure the regulator output. If +5 V is there, measure +5 V at pin 4 of the RF modulator. If that is missing, L205 or the track from A203 to the modulator is open; if it is present, the RF modulator or the RF cable is at fault.[4]
  3. If the output is not +5 V, measure the regulator input. Atari expects about 7.5 V unregulated there. If the input is present and the output is not, the regulator is defective.[4] Farquhar treats any reading more than about 0.15 V away from 5 V as a bad regulator.[13]
  4. If the input is missing, measure the unregulated supply at the power jack J201. If it is present at J201 but not at the regulator input, the fault is between the two: the power switch S201 or the track. Atari's symptom checklist for a snowy CX2600A names A203, S201, the RF module and L205.[4][21]
  5. If there is no unregulated supply at J201, check whether the +5 V line is shorted to ground and repair any short. If it is not shorted, Atari's chart swaps the TIA (A201), the 6507 (A200) and the 6532 (A202) in turn and, if there is still no modulation, replaces J201.[4]

Following the supply on a CX2600

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Atari 2600 channel 3 switchboard schematic (FSM figure 2-4)
The channel 3 switchboard: J101 pin 2 brings the unregulated supply to C106 and S101, A101 regulates it, and +5 V returns on pin 1 (field service manual figure 2-4)

On the six-switch console Atari first swaps in a known-good switchboard to decide which board is at fault.[3] Without a spare switchboard, measure both boards with the 12-way cable connected.

Motherboard side:[3]

  1. Measure +5 V at J201 pin 1. If it is there, the motherboard is receiving its supply.
  2. If it is not, measure +9 V at J201 pin 2. If +9 V is present and +5 V is not, Atari's chart swaps the 6532 (A202), the 6507 (A200) and the TIA (A201) in turn.
  3. If there is no +9 V, check continuity across J201 pin 2. Replace J201 if it is open.
  4. Measure 7.5 to 9.0 V at the power jack J204, on the underside of the board. If it is present, look for an open track between J204 and J201. If it is missing and J204 is good, the supply is shorted to ground; if J204 is faulty, replace it.
  5. If the supply still does not reach the switchboard, check continuity through J201 pins 1, 3, 6, 10 and 11, then check the +5 V line for a short to ground. Observe the meter's polarity: Atari warns not to put the positive probe on ground. Look for shorted tracks and solder bridges, then for shorted capacitors among C204, C201, C220, C239, C200 and C214.[22]

Switchboard side:[23][24]

  1. Measure +5 V at J101 pin 1. If it is present, check for +5 V at the RF modulator's supply pin (pin 3 of a five-pin modulator, pin 2 of a three-pin one); if that is missing, the track from A101 pin 3 is open. Then check that modulator pin 1 has continuity to ground through J101 pins 6 and 10.
  2. If J101 pin 1 has no +5 V, measure the regulator output, A101 pin 3. If +5 V is there, J101 or the track between A101 and J101 is faulty.
  3. Measure the regulator input, A101 pin 1, for 7.5 to 9 V unregulated. If it is present and the output is not, the regulator is bad or its ground connection is open.
  4. If the input is missing, measure 7.5 to 9 V on the J101 side of the power switch S101. If it is there, replace S101.
  5. If it is not, check J101 pin 2 for continuity and for a short to ground, and replace J101 if either fails. Then check C103 and C106 for a short to ground.
  6. If +9 V is present at J101 pin 2 and +5 V is missing at pin 1, check C101 for a short and replace it; if C101 is good, replace A101. If there is no +9 V at J101 pin 2, check that J101 pins 1 and 2 are not shorted to ground and that C101, C103 and C106 are not shorted.

Replacing the regulator

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Farquhar's method, with the orientation note from the Vintage Gaming and More kit guides:[13][16][19]

  1. Unplug the adaptor. Remove the screw that holds the regulator to the board and keep it.
  2. Bend the regulator straight up and cut its legs close to its body, leaving enough of each leg to grip.
  3. Heat each joint from the underside and pull the leg out with needle-nose pliers when the solder melts. Clear the holes.
  4. Clean the old heatsink compound off the board with isopropyl alcohol.
  5. Put a small dab of fresh compound where the old compound was. Do not use a whole packet.
  6. Fit the new regulator in the same orientation as the old one, with its fixing hole over the screw hole, and bend it down onto the board.
  7. Refit the screw.
  8. Solder the three legs from the underside, using flux so that each joint takes less than about ten seconds, and trim the excess.
  9. Clean the joints with isopropyl alcohol.

On early CX2600s with a standup regulator on a heatsink, Atari's tech tip 19 asks for a check for hairline cracks between the regulator and the switchboard, and for the regulator to be held firmly to the heatsink by its Tinnerman clip.[9]

Repairing the power jack

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Atari 2600 CX2600A power jack J201 (Rev 16)
J201, the 3.5 mm power jack on a Rev 16 four-switch board, with C242 beside it (photo: Evan-Amos, public domain)
  1. With the board out, turn it over and look at the two solder joints under the power jack.[2]
  2. Reflow any that are dull or cracked with the iron, adding a little fresh solder. The finished joints should be shiny and unbroken, and the jack should not move when pushed by hand.[2]
  3. Check the other joints on the underside while the board is out and reflow any that are dull or cracked.[2]
  4. If the picture still drops out when the plug is moved in a small circle, replace the jack.[9]

Power switch

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Farquhar first works a dirty power switch back and forth about 100 times with the power off, then sprays contact cleaner into the opening in the side of the switch, works it again and lets it dry for 30 minutes.[2] Opening, cleaning and replacing the slide switches is covered in Atari 2600 Console Switch Repair.

CX2600 interconnect cable

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Two types of 12-way cable were used between the motherboard and the switchboard: a flat-wire cable with a female connector that plugs onto a male 12-pin connector on the switchboard, and a ribbon cable with a male connector that plugs into a female 12-pin socket. Atari's December 1981 bulletin replaces a faulty flat-wire cable with the ribbon cable, part C012776, and the switchboard's male connector with the female socket, part C014778-03.[25] Tech tip 13 asks for both J201 and J101 to be checked for a secure fit, and tip 5 checks pins 3, 6 and 10 of J101 for continuity if the ground line carries about 1 V of noise.[9]

Testing

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  • With the console reassembled and a game running, the regulator output should read 5 V.[13] Check it on the adaptor you will use: the used 7805 that retro64 fitted gave 5 V on a home-built supply and about 6 V on the original Atari adaptor.[15]
  • Move the power plug in a small circle with a game running; the picture should not drop out.[9]
  • Atari's procedures end every repair with a burn-in of at least two hours.[14]
  • Tynemouth Software measured about 350 mA drawn by a working six-switch console, about 1.4 W in the regulator from a 9 V input.[26]

Board variations

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  • Atari's manual lists variations on the CX2600 channel 3 switchboard: C102 may or may not be fitted, and C103 and C104 may be missing, 0.22 µF dipped mylar or 0.01 µF ceramic.[27]
  • The channel 3 switchboard has a 680 Ω 2 W resistor, R101, connected across the regulator, and the channel 3 and channel 2-3 switchboards use different heatsinks.[6][1]
  • On the CX2600A, C241 and C242 are 0.1 µF parts between the jack and the regulator. Atari's February 1982 bulletin replaces leaking ones with parts rated at 50 V or more.[11]
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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 Atari, Field Service Manual FD100133 Rev. 02, Section 8, CX2600 and CX2600A parts lists, pp. 8-1 to 8-8: regulator 78M05 C014348 at A101 and A203, 2200 µF 16 V C014373 at C106 and C243, jack 79-5918 at J204 (CX2600) and J201 (CX2600A, 3.5 mm), R101 680 Ω 2 W and the two switchboard heatsinks.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Dave Farquhar, "Atari 2600 won't turn on? Try this.", The Silicon Underground, 26 June 2019, updated 19 January 2025. The four usual causes, the large capacitor and how he discharges it, adaptor voltages, switch cleaning, reflowing the power jack, and measuring the 7805 with the black lead on its screw.
  3. ↑ 3.0 3.1 3.2 Atari, Field Service Manual FD100133 Rev. 02, "Snowy Screen Troubleshooting Procedure, Motherboard", p. 4-11: J201 pins 1 and 2, the power jack J204 at 7.5 to 9.0 V, and the swap-out of A202, A200 and A201.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Atari, Field Service Manual FD100133 Rev. 02, "2600A Snowy Screen Troubleshooting Procedure", p. 6-12: +5 V at A203's output and RF module pin 4, L205, 7.5 V at A203's input and at J201, a shorted +5 V line, the swap-out of A201, A200 and A202, and J201.
  5. ↑ Atari, Inc., Video Computer System Field Service Manual, Domestic Model 2600/2600A, FD100133 Rev. 02, Section 1, "Theory of operation", pp. 1-3 to 1-5: the switchboard's power supply, the 12-conductor cable and the 2600A's single board. Hosted as File:Atari 2600 and 2600A Field Service Manual.pdf; see Atari 2600 and 2600A Field Service Manual.
  6. ↑ 6.0 6.1 6.2 Atari, Field Service Manual FD100133 Rev. 02, figure 2-4, "2600 Channel 3 Switchboard Schematic", p. 2-7: J101, S101, C106 2200 µF on pin 2, A101 with R101 across it, C101 to C105.
  7. ↑ 7.0 7.1 Atari, Inc., Video Computer System (Main Board) schematic, CX-2600A, sheet 2 of 4, 30 May 1982: external power jack, 0.1 µF and 2200 µF 16 V ahead of the power switch, 7805 regulator. Hosted as File:Schematic Atari2600A 2000.png.
  8. ↑ 8.0 8.1 Atari, Field Service Manual FD100133 Rev. 02, 2600 diagnostic flowchart, p. 4-3: snow with no modulation; check the connections to the television, then test with a known-good battery eliminator.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 Atari, Field Service Manual FD100133 Rev. 02, NTSC technical tips at the back of the manual, pp. 7-2 to 7-4: tip 5 (floating ground, J101 pins 3, 6 and 10), tip 8 (power jacks), tip 13 (J201 and J101 fit) and tip 19 (standup regulator).
  10. ↑ 10.0 10.1 Best Electronics, "What to look for when buying a used or third party reconditioned Atari 2600 / 2600A / 2600Jr console", tips 5 (switch tests) and 7 (power jack and adaptor lead test).
  11. ↑ 11.0 11.1 Atari, service bulletin for the 2600A, February 1982: RF interference, lines and hum caused by a leaking or defective C241 or C242 (0.1 µF) between the power jack and the regulator; replacements rated at 50 V or greater. In Field Service Manual FD100133 Rev. 02 (PDF p. 155).
  12. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Black or Solid Colored Screen Troubleshooting", p. 4-9: clock checks at A202, A201 and A200.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 13.5 13.6 Dave Farquhar, "Atari 2600 voltage regulator troubleshooting and replacement", The Silicon Underground, 23 March 2020, updated 19 January 2025. Readings on the regulator (within about 0.15 V of 5 V) and his replacement method.
  14. ↑ 14.0 14.1 Atari, Field Service Manual FD100133 Rev. 02, Section 4 introduction, p. 4-1: burn-in for at least two hours after every repair; the LSI chips' sensitivity to static and the grounding strap.
  15. ↑ 15.0 15.1 retro64, "Atari 2600 and 7800: repair tales": a used 7805 that gave about 6 V on the original Atari adaptor, cured with a new regulator.
  16. ↑ 16.0 16.1 Vintage Gaming and More, "Atari 2600 4 Switch Tune Up Kit Installation Guide": opening the four-switch console and replacing C243, C241, C242 and the regulator at A203 in the same orientation, with a small amount of thermal paste.
  17. ↑ 17.0 17.1 17.2 Dave Farquhar, "How to disassemble an Atari 2600 VCS", The Silicon Underground, 20 February 2020, updated 19 January 2025. Screw positions and angles, board removal on four-switch and six-switch models, and the parts outside the shield.
  18. ↑ Evan-Amos, "Atari-2600-Four-Switch-Motherboard-Flat.jpg", Wikimedia Commons, public domain: a Rev 16 CX2600A board with A203 and J201 outside the shield.
  19. ↑ 19.0 19.1 Vintage Gaming and More, "Atari 2600 6 Switch Tune Up Kit Installation Guide": the eight case screws, separating the switchboard from the motherboard, and replacing C106 and the regulator at A101.
  20. ↑ Atari, Field Service Manual FD100133 Rev. 02, figure 2-1, "2600/2600A IC Pinouts", p. 2-3: regulator pins in, ground, out.
  21. ↑ Atari, Field Service Manual FD100133 Rev. 02, Section 5, 2600A symptom checklist, p. 5-5: snowy screen, A203, S201, RF module, L205.
  22. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Snowy Screen Troubleshooting Procedure, Motherboard (Continued)", p. 4-12: continuity of J201 pins 1, 3, 6, 10 and 11, the +5 V short check with the polarity caution, and capacitors C204, C201, C220, C239, C200 and C214.
  23. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Snowy Screen Troubleshooting Procedure, Switchboard", pp. 4-18 and 4-19: J101 pin 1, the RF modulator supply pin, A101 pins 1 and 3 at 7.5 to 9 V in and +5 V out, S101 and J101 pin 2.
  24. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Colored Screen Troubleshooting Procedure, Switchboard (Continued)", p. 4-17: +9 V at J101 pin 2, C101, C103, C106 and the regulator A101.
  25. ↑ Atari, service bulletin, 9 December 1981, "Compatibility problems between the cable and connectors linking 2600 Mother Board to the switch board", in the service bulletins section of Field Service Manual FD100133 Rev. 02 (PDF p. 154).
  26. ↑ Dave Curran, "Atari 2600 Black Screen Repair", Tynemouth Software, February 2015: about 350 mA drawn by a working six-switch console.
  27. ↑ Atari, Field Service Manual FD100133 Rev. 02, p. 2-6: variations on the 2600 channel 3 and channel 2-3 switchboards.


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