From TechWiki
Revision as of 10:51, 25 June 2018 by Luke (talk | contribs) (Opening the Power Supply)
Jump to: navigation, search

Chips & ICs

Colecovision Console

Power Supply

  • IC1: Voltage Regulator: CA723CE
  • IC2: Voltage Regulator: CA723CE
  • IC3: -5v Regulator: 7905C (with mica insulator)
  • IC?: TIP41
  • IC?: TIP41


These excellent schematics were drawn by Dan Boris

Common Problems

Graphics are corrupted, text is unreadable. Random blocks appear and game characters can interact or be blocked by them.
Dirty power switch. Switch must be disassembled, contacts cleaned / burnished, and reassembled.
Defective power supply
VRAM failure. All 8 VRAM chips use 3 voltage power and are known for running hot and developing issues over time. A +5v memory kit and replacement instructions are available.
TMS9928 failure. These chips tend to run hot and if the heat sink has fallen off they may have become damaged over time. The 9928 was used in arcade hardware but in the Colecovision doesn't seem circulate air well OR they are prone to static damage.

Dysfunctional Controller Chips

If your Colecovision isn't behaving correctly, games start by themselves, or they behave as if one controller direction is pressed down constantly, the U18 / U19 74LS541 chips have probably been static fried. Purchase new controllers chips as a kit

Technical Tips (From Service manual)

Black out on screen
If the screen blacks out after the game has been played for a short interval, check C106 for proper polarity. If polarity is wrong, replace C106
Purple Monkey
In Donkey Kong, if the monkey, Mario, and the barrels are purple, rather than their normal colors, replace U9
Joystick Game Selection
If the keypad does not control the game selection, only the joystick can be used to select games, replace U6 (also see Common Problems section above)
Channel 3 but not 4
Channel 3 operates normally but channel 4 only works if the game is turned off and then turned back on again, (or vise versa) replace RF board.
Not all cartridges function
Game does not accept all and/or any cartridges. Examine C70 for mechanical obstructions. Is it flopped over flat on board? Replace U5.
Vertical lines
Vertical lines on background rather than solid blue background with no lines. Replace C106.
Skips menu
Menu is skipped. This is the blue screen with skill levels. Check pins 3-9 of U18 with DVM. If any pin is below 2.2VDC change U18. Check pins 2-8 of U19 with DVM. If any pin is below 2.2VDC change U19.
No explosion
If there is no explosion, a sound testing of the noise generator, on the final test, replace U20.
12 VDC is shorted to -5 VDC
Examine WJ2 to see if it has shorted to adjacent test points.
No RF voltage
If there is no voltage on the RF board, check WJ2.
No Color
If color has disappeared, check frequency at J4 pin 6. Correct frequency is 3.57954 Mhz +/- 100 Hz. If the frequency is incorrect, check the clock circuit.
Double images
Replace U9 for double images.
Wavey (sic) picture
If picture is wavy, ensure that R62 is 270Ω and C90 is 120pF. If they are incorrect, replace them. Check Q2, if it is an ITT transistor, replace it.
Incorrect scoring
If scoring is not working properly, replace U3 and/or U4.
Wrong frequency
3.579 Mhz clock is the wrong frequency. If U22 is a Texas Instruments IC, replace it.
Bad spinner interface
Spinner interface is not working. If U24 is a Texas Instruments IC, replace it.
Slow game
If game is running abnormally slow, replace U20.

RF Adjustment / Alignment

Colecovision-RF-Alignment-Map.jpg Lower left adjustment is for channel "B". There is no separate adjustment for channel "A". Upper-right adjustment is for audio subcarrier.

+5 Volt RAM Modification

HOWTO: 5 Volt RAM Modification

No-delay BIOS Modification

HOWTO: BIOS Replacement

Opening the Power Supply

It's not quite an easy job as the two case halves were glued / plastic welded when built.

Here are a few potential methods:

  1. Cut the case apart with a saw or Dremel tool. If you can place the supply in a vice, using a fine-tooth hacksaw right in the groove where the two halves meet should produce fairly clean results.
  2. Hit with a hammer around the perimeter to break the glue/welds. Probably not the most effective and risks a full fracture through the case.
  3. Use a hot-wire cutter and some wedges to separate the case. Cuts cleanly but a little challenging as the ABS tends to melt itself back together - creative use of wedges may help. Avoid penetrating further than 6-7mm or you may cut into the transformer case or transformer wires.

If you want to avoid cutting near the output wire, you really only need to separate the sides & top of the case. Once they are free you can pry the case open and snap the bottom fairly cleanly.

Look over the existing soldering for flaws. The few I've seen have had some sketchy looking solder joints, improper fills, things like that.

Capacitor List

Colecovision Console

[Purchase these parts as a kit]

Revision J

C3	1uF	50v
C16	10uF	16v
C34	10uF	16v
C36	10uF	16v
C68	10uF	16v
C87	10uF	16v
MOD	10uF	50v (on modulator PCB)

Power Supply

PC-016-1 (110v US NTSC giant brick)

Remember to retain the mica insulator when replacing the 7905 regulator!


C1	1000uF	25v
C2	4700uF	16v
C3	220uF	25v
C4	1000uF	16v
C7	22uF	50v
C8	22uF	50v
C9	22uF	50v