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Atari 2600 TIA, 6507 and 6532 Replacement

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Atari 2600 four-switch motherboard with shield top removed
The three LSI chips of a four-switch board with the shield top off: the 6532 (C010750-03) beside the cartridge connector, the 6507 (C010745-03) and the TIA (C010444D-03) (photo: Evan-Amos, public domain)

The Atari 2600 is built round three large chips: the 6507 processor (A200), the TIA (A201), which makes the picture and sound, and the 6532 RAM, I/O and timer chip (A202). On both the six-switch CX2600 and the four-switch CX2600A they sit in sockets.[1][2] When the console gives a black or solid-coloured screen with a good +5 V supply, Atari's service procedure checks the clock signals from chip to chip and then swaps the three chips one at a time with known-good parts.[3][4] Dave Curran of Tynemouth Software found the TIA to be the usual culprit in a black-screen 2600, and points out that the only source of replacement TIAs and 6532s is another 2600.[5]

Symptoms

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  • Black or solid-coloured screen, with the console's +5 V supply present. If the supply is missing, start with Atari 2600 Power Supply Circuit Repair.[3]
  • Diagonal lines on the screen when Atari's Diagnostic Test Cartridge starts: Atari's RAM test treats any diagonal lines as a failed 6532 (A202). The test does not check the 6532's I/O ports or timer.[6]
  • Vertical lines: Atari's checklist lists A200, A201, A202, the cartridge connector J200, or an open or shorted address or data line.[7]
  • A console that runs everything except Indy 500: tech tip 7 says pin 23 of A202 is probably shorted to a data line.[8]
  • A four-switch console that shows a black screen only when it is switched off and quickly back on: Atari's tech tip 16 of 9 August 1983 (below).[9]
  • Intermittent colour or graphics faults on boards with Molex sockets fitted with insertion aids (tech tip 4).[8]
  • Faults that appear as the console warms up. Best Electronics leaves a game running for three to five minutes until the screen starts changing colour on its own (the console's attract mode) and has seen many consoles glitch, reset or lose the picture as the chips heat up.[10]

Handling the chips

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Atari warns that A200 to A203 are very sensitive to static electricity. Keep them in carrier tubes or on conductive foam, wear a grounding band, and use a chip puller: never prise them out with a screwdriver or any other tool, because the stress of removal and insertion also damages them.[11]

Tools and parts

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The three chips (Atari numbers)
Chip Designator Atari number Socket
6507 processor A200 C010745 28 pins (C014386-08)
TIA A201 C010444 (NTSC) 40 pins (C014386-09)
6532 RAM, I/O and timer A202 C010750 40 pins (C014386-09)

The numbers are from Atari's parts lists.[2] The TIA differs between television standards; Tynemouth Software's PAL console had a TIA marked C011903, and the 6507 and 6532 in it carried the same Atari numbers as above.[5] Atari's procedure needs known-good chips to swap in, a 15 MHz oscilloscope and, ideally, the Diagnostic Test Cartridge.[12]

Procedure

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Getting to the chips

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  1. Open the console and take the board out as in Atari 2600 Power Supply Circuit Repair#Opening the console.[13][14]
  2. Four-switch CX2600A: bend up the four tabs round the metal shield with needle-nose pliers and lift off the top of the shield.[13] Six-switch CX2600: remove the six screws from the bottom of the motherboard's metal case and the two screws holding the board to its top.[14]

Checking power to the chips

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Atari 2600 and 2600A IC pinouts (FSM figure 2-1)
Pin numbering of A200 (28 pins), A201 and A202 (40 pins), top view (field service manual figure 2-1)
  1. Power the board and check +5 V and ground on every chip.[4]
Supply pins (Atari CX-2600A schematic)
Chip +5 V Ground
6507 (A200) Pin 4 Pin 2
TIA (A201) Pin 20 Pin 1
6532 (A202) Pin 20 Pin 1

The pins are from Atari's CX-2600A schematic.[15] A missing supply on one chip is an open track to +5 V or ground, or a bad regulator.[4]

Checking the clocks

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The oscillator drives the TIA at pin 11; the TIA sends φ0 from pin 4 to the 6507 at pin 27; the 6507 sends φ2 from pin 28 to the TIA at pin 26 and the 6532 at pin 39. Atari's charts look for a 4 to 5 V peak-to-peak signal at each point in turn, starting at the 6532.[3][4][15]

Clock checks, 4 to 5 V peak to peak at each point
Point If the signal is missing (CX2600, p. 4-9) If the signal is missing (CX2600A, p. 6-10)
φ2 at A202 pin 39 Go to the next check Go to the next check
Oscillator, between C203 and R203 (CX2600) or R202 and R204 (CX2600A) Swap X200, Q200, Q201, then the other clock parts Change X200, Q200, then the other clock parts
Oscillator at A201 pin 11 Open between C203 and pin 11 Open between R204 and pin 11
φ0 at A201 pin 4 Swap A201, then A200; if still missing, pin 4 is shorted Swap A200, then A202; if still missing, pin 4 is shorted
φ0 at A200 pin 27 Open between A200 pin 27 and A201 pin 4 Same
φ2 at A200 pin 28 Swap A200, then A202; if still missing, pin 28 is shorted Swap A201, then A200; if still missing, pin 28 is shorted to ground
φ2 at A201 pin 26 Open between A201 pin 26 and A200 pin 28 Same
All present but no φ2 at A202 pin 39 Open between A202 pin 39 and A200 pin 28 Same

The two charts differ in the order of the chip swaps; the table follows each.[3][4]

If the clocks are present at every point, Atari's chart checks φ2 at A201 pin 26, the supply to A200 to A203, and the reset and ready lines for opens and shorts, and then swaps the chips.[4][16]

Reseating and swapping the chips

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  1. With the power off, reseat each chip with a chip puller. Tynemouth Software notes that reseating often helps, although it did not on the console in its write-up.[5]
  2. On boards with Molex sockets that have insertion aids, remove the aids and reseat the chips (tech tip 4).[8]
  3. If the fault remains, swap the chips one at a time with known-good parts in the order the chart gives for your board: A200, A202, A201 for a black screen on either board once the clocks are good.[16][4]
  4. Leave each known-good chip in place when it does not cure the fault, and go on to the next.[11]
  5. When the fault clears, put the removed chips back one at a time to find out which were really faulty. Atari's method avoids replacing good chips needlessly.[11]

Replacing damaged sockets

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retro64 found a 2600 whose three sockets had contacts spread too far apart (pin 22 of the 6532's socket among them) to grip the chips, so that games crashed very often. Replacing the sockets put the console back in working order.[17] Inspect each socket's contacts; if they are spread or corroded, desolder the socket and fit a new one of the same pin count (28 for A200, 40 for A201 and A202).[17][2]

Four-switch reset fix (tech tip 16)

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Atari 2600 four-switch motherboard (Rev 16)
A Rev 16 four-switch board; the 555 timer added to the reset circuit at that revision is the small eight-pin chip at upper right (photo: Evan-Amos, public domain)
  1. On a four-switch console that shows a black screen after a quick off-and-on, find R227.[9]
  2. Desolder the 24 kΩ resistor (Atari 14-5243) and fit a 110 kΩ resistor (Atari 14-5114) in its place.[9]

Atari's tip 16 names the problem as a power-on reset fault of the C010750, the 6532.[9] Boards of revision 16 and later add a timer chip, A205, to the processor's reset circuit, which Atari says eliminates power-on reset failures.[1]

Testing

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  • Run the Diagnostic Test Cartridge's tests: no diagonal lines at power-up (6532 RAM), steady colour bars, eight grey bars in black and white, the matrix test with and without the shorting plugs, and the audio tones.[6]
  • Without the test cartridge, play several games and leave one running in attract mode for some minutes, as Best Electronics does, to see whether the fault returns as the chips warm up.[10]
  • Atari burns every repaired console in for at least two hours.[11]
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References

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  1. ↑ 1.0 1.1 Atari, Inc., Video Computer System Field Service Manual, Domestic Model 2600/2600A, FD100133 Rev. 02, Section 1, pp. 1-4 to 1-6: the MPU, RAM-I/O and TIA chips, and the timer chip A205 added to the reset circuit from revision 16. Hosted as File:Atari 2600 and 2600A Field Service Manual.pdf; see Atari 2600 and 2600A Field Service Manual.
  2. ↑ 2.0 2.1 2.2 Atari, Field Service Manual FD100133 Rev. 02, Section 8 parts lists, pp. 8-2 and 8-6 to 8-7: A200 6507 C010745, A201 TIA C010444, A202 6532 C010750, sockets C014386-08 (28 pins) and C014386-09 (40 pins).
  3. ↑ 3.0 3.1 3.2 3.3 Atari, Field Service Manual FD100133 Rev. 02, "Black or Solid Colored Screen Troubleshooting", p. 4-9.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Atari, Field Service Manual FD100133 Rev. 02, "2600A Solid Colored Screen Troubleshooting", pp. 6-10 and 6-11.
  5. ↑ 5.0 5.1 5.2 Dave Curran, "Atari 2600 Black Screen Repair", Tynemouth Software, February 2015: reseating, the TIA as the usual culprit, donor parts, and the chip markings C010750, C011903 (PAL TIA) and C010745.
  6. ↑ 6.0 6.1 Atari, Field Service Manual FD100133 Rev. 02, "RAM Test" and the other Diagnostic Test Cartridge tests, pp. 3-8 to 3-14.
  7. ↑ Atari, Field Service Manual FD100133 Rev. 02, Section 5 symptom checklists, logic failures, pp. 5-2 and 5-5.
  8. ↑ 8.0 8.1 8.2 Atari, Field Service Manual FD100133 Rev. 02, NTSC technical tips at the back of the manual: tip 4 (Molex sockets), p. 7-1, and tip 7 (Indy 500), p. 7-2.
  9. ↑ 9.0 9.1 9.2 9.3 Atari, Tech Tip 16, 9 August 1983, "Power-On reset problem of the C010750", for the 2600A (CA015911): R227 changed from 24 kΩ (14-5243) to 110 kΩ (14-5114). 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; see Atari 2600 and 5200 Field Change Orders and Tech Tips.
  10. ↑ 10.0 10.1 Best Electronics, "What to look for when buying a used or third party reconditioned Atari 2600 / 2600A / 2600Jr console", tip 6: attract ("Video Attack") mode after three to five minutes, and consoles that fail as the chip set heats up.
  11. ↑ 11.0 11.1 11.2 11.3 Atari, Field Service Manual FD100133 Rev. 02, Section 4 introduction, p. 4-1: the swap-out procedure, handling the chips and the two-hour burn-in.
  12. ↑ Atari, Field Service Manual FD100133 Rev. 02, "Equipment Requirements", p. 3-1.
  13. ↑ 13.0 13.1 Vintage Gaming and More, "Atari 2600 4 Switch Tune Up Kit Installation Guide": opening the four-switch console and bending up the shield tabs.
  14. ↑ 14.0 14.1 Vintage Gaming and More, "Atari 2600 6 Switch Tune Up Kit Installation Guide": getting the six-switch motherboard out of its case.
  15. ↑ 15.0 15.1 Atari, Inc., Video Computer System (Main Board) schematic, CX-2600A, sheet 2 of 4, 30 May 1982: supply pins of the 6507 (pin 4), TIA (pin 20) and 6532 (pin 20). Hosted as File:Schematic Atari2600A 2000.png.
  16. ↑ 16.0 16.1 Atari, Field Service Manual FD100133 Rev. 02, "Black or Solid Colored Screen Troubleshooting (Continued)", p. 4-10.
  17. ↑ 17.0 17.1 retro64, "Atari 2600 and 7800: repair tales": a 2600 with damaged chip sockets, cured by new sockets.


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