Coleco Mini-Arcade Troubleshooting
Fault-finding on Coleco's VFD Mini-Arcade tabletops: Pac-Man, Galaxian, Frogger, Donkey Kong and Ms. Pac-Man. They share one construction: a single microcontroller drives a vacuum fluorescent display (VFD) directly, a small transformer and transistor circuit makes the display's higher voltage from the four C cells, and the controls are leaf switches on the main board.[1][2][3][4] Opening the case is described on Coleco Mini-Arcade Maintenance, and display procedures on Coleco Mini-Arcade VFD Repair.
Owners who have asked for a schematic on the KLOV and Build Your Own Arcade Controls forums found none.[2][5]
Before you start
[edit | edit source]- Fit fresh alkaline C cells. Coleco's guides say the game does not work properly on weak cells and that an erratic display or erratic play may be the only sign.[6][7]
- If you use an adapter, check its polarity first. Reverse polarity is the usual cause of a blown transistor in these games.[3]
- The display supply gives a mild shock if you touch it with the game on. It will not hurt you, but it can make you drop the game.[3]
- Check that the speaker cone is in place before deciding the sound is weak. The bare piezo buzzer is much quieter.[8]
Symptom checklist
[edit | edit source]| Symptom | Probable cause | Action |
|---|---|---|
| Erratic display or play | Weak cells | Fit fresh alkaline C cells[6] |
| Dead: no display, no sound | Flat cells, corroded contacts, a broken battery lead, the power switch, a failed transistor | No power below[3] |
| Dead, and a transistor gets hot within seconds | Failed transistor, often after reverse polarity | Switch off at once; remove and test every transistor[3] |
| Sound but no display | Broken display glass or exhaust tip; no display supply (transformer or its transistor); a bad display joint | Sound but no display below[3] |
| A row or block of the display missing | Cold joint at the display pins or the microcontroller; a corroded trace | Reflow the display pins; trace the line from the display to the microcontroller[3][9] |
| A vertical strip slightly dimmer than the rest | Broken filament inside the display | None; the tube is damaged[3] |
| Display getting dimmer over time | Display wear | See Coleco Mini-Arcade VFD Repair[3] |
| No sound, display normal | Speaker wire off at the buzzer or the board | Re-solder the two PZ wires[1][10] |
| Player keeps moving one way, or one direction dead | Leaf switch worn through, broken or stuck down | Replace the leaf[1] |
| Joystick needs a hard press, or the player jumps two or three places | Dirty contacts | Clean the leaves and pads[10] |
No power
[edit | edit source]- Measure the voltage where the battery leads join the board, red at B+ and blue at B−, with cells fitted and the game off.[3][1]
- Switch on and check that the voltage passes through the power switch. Bridging the switch is a quick test.[3]
- If power reaches the board but goes no further, suspect the transistors. On the Pac-Man board in the Handheld Museum's guide there are two, a round one (circled in its photograph) and a square one below it. Remove them and test them with a meter. The author reports fixing many dead games this way and describes the transistors as acting almost like fuses.[3]
- If one transistor is hot, replace or test all of them: a bad part elsewhere may have overheated it, and a new transistor fitted alone can fail the same way.[3]
- Check the traces for corrosion and breaks. Then test the resistors, diodes and capacitors. If everything tests good and the board is undamaged, the microcontroller has probably failed and the game needs a donor board.[3]
The Galaxian in the Build Your Own Arcade Controls thread shows how far this can go: new transistors, new capacitors and repaired tracks brought back faint sound but not the display.[5]
Sound but no display
[edit | edit source]Sound shows that the microcontroller is running. The display itself, its supply or its joints are at fault.[3]
- Look for loose pieces of glass, and check the display's exhaust tip, the small glass nipple where the tube was evacuated. Any hole in the envelope ruins the display.[3]
- Listen to the transformer with the game on. A working one usually makes a faint high-pitched whine.[3]
- Check the transistors as above. On a Pac-Man, a KLOV member whose board had lost its switching transistor fitted a TIP41C NPN transistor in its place, and the game worked.[2]
- If the supply is working, look for a bad joint at the display pins. A completely dead display is usually down to one of the first two or last two pins on each side.[3]
The procedures for finding bad display joints and for checking the tube are on Coleco Mini-Arcade VFD Repair.
Part of the display missing
[edit | edit source]A missing row or block is almost always a bad joint between the display and the board, or between the microcontroller and the board. Less often a trace has broken or the display has partly failed.[3] In the Handheld Museum's Pac-Man, a whole row was missing because the copper of the trace from grid pin G4 to the microcontroller had corroded through; a short wire soldered over the gap fixed it.[3] A KLOV member fixed a Frogger with missing lines by reflowing the display's solder joints.[9]
Controls
[edit | edit source]- Player always moving in one direction: a leaf switch under the joystick is stuck down or has broken.[1]
- One direction dead: the leaf for that direction has worn through.[1]
- A joystick that needs to be pressed hard, or moves the player two or three places: clean the contacts.[10]
- A stick that is hard to control: check that the X-shaped guide under it is present.[1]
Sound
[edit | edit source]The Mini-Arcade site finds a broken speaker wire the most common cause of lost sound. Each wire should be soldered to one of the two discs of the buzzer at one end and to the board at the other.[10] On these games the board pads are both marked PZ, and polarity does not matter.[1]
Things that are not faults
[edit | edit source]- A black or silvery burn mark about half an inch across inside the display is normal.[3]
- A faint whine from the transformer while the game is on is the display supply working.[3]
- Galaxian goes into a demo when switched on. Press the left control stick to the left to choose Galaxian.[7]
- Frogger at Skill 1 shows no snake until all the homes have been filled once.[11]
- Donkey Kong started with the joystick held up begins a game at once, at a "level 0" whose completion bonus is zero, with extra lives. This start was found by Luca Antignano while writing a simulator of the game.[12]
Model notes
[edit | edit source]Donkey Kong
[edit | edit source]Hitachi HD38820A45 microcontroller in a flat package on board "Coleco Rev C 75790 DK", with a Futaba DM-47ZK 2K display. The speaker volume decays through an RC circuit.[4]
Frogger
[edit | edit source]Mitsubishi M58846-701P microcontroller with a 600 kHz crystal on a board made in Japan ("Coleco Frogger Code No. 01-81543, KS-003282 Japan"), and an Itron CP5090GLR R1B display.[13] A Frogger with missing lines has been fixed by reflowing the display joints.[9]
Galaxian
[edit | edit source]Hitachi HD38800A70 microcontroller on board "Coleco Rev A 75718", with a Futaba DM-36Z 2H display. Galaxian also has a discrete sound circuit for the attacking aliens' whine, separate from the microcontroller's 1-bit sound.[4] A KLOV member's Galaxian with no power had battery voltage at the board, and its small transformer is marked "800".[14] The Build Your Own Arcade Controls thread above is also a Galaxian.[5]
Pac-Man
[edit | edit source]The Handheld Museum's repair guide was written on a Pac-Man, board 75690, with an HD38820A28 microcontroller and a Futaba DM-34Z display.[3][15] On that board the two transistors are T1 and T2. A KLOV member's Pac-Man had lost the switching transistor that works with the display transformer, and a TIP41C NPN transistor in its place brought the game back.[2] Games with the A28 program do not show the whole maze at switch-on; this is normal.[15] Pac-Man notes: Coleco Pac-Man Mini-Arcade Troubleshooting.
Ms. Pac-Man
[edit | edit source]Board 911171 with an HD38820A61 and a Futaba DM-60Z 3I display.[15] The right stick is player 1 and selects the game: left for Ms. Pac-Man, down for Head-to-Head, up for the demonstration. A game that does not respond to the left stick at switch-on is therefore normal.[16] A KLOV member's Ms. Pac-Man had one vertical line of the display missing; the owner suspected a cold solder joint, and no outcome was reported.[9] Ms. Pac-Man notes: Coleco Ms. Pac-Man Mini-Arcade Troubleshooting.
Related pages
[edit | edit source]- Coleco Mini-Arcade Maintenance
- Coleco Mini-Arcade VFD Repair
- Coleco Mini-Arcade Instruction Manuals
- Battery Explosion, Capacitor or Corrosion Damage
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Handheld Museum, "Coleco Game Repair", page 2 (retrieved 2026-10-06): the four wires to the board (B+, B− and two marked PZ), the joystick parts and leaf switches, and the display lens screws.
- ↑ 2.0 2.1 2.2 2.3 KLOV forums, "PACMAN Coleco repair : component information", August–September 2011 (retrieved 2026-10-06). Community thread: a Pac-Man with the switching transistor missing; the owner traced it as the converter's switching transistor working with the transformer and fitted a TIP41C NPN transistor, after which the game worked.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22 Handheld Museum, "Coleco Game Repair (Pac Man, Ms. Pac Man, Donkey Kong, Frogger & Galaxian)", page 3 (retrieved 2026-10-06). Community repair guide written on a Pac-Man: no power (wires, switch, transistors, reverse polarity), no display with sound (display damage, the high-voltage transformer, display joints), partial display (cold joints, corroded traces), filaments and grids, and the trace repair on the G4 grid line.
- ↑ 4.0 4.1 4.2 MAME source, hh_hmcs40.cpp (retrieved 2026-10-06), driver notes and port mapping for Coleco Donkey Kong (PCB "Coleco Rev C 75790 DK", Hitachi HD38820A45, Futaba DM-47ZK 2K) and Coleco Galaxian (PCB "Coleco Rev A 75718", Hitachi HD38800A70, Futaba DM-36Z 2H); the microcontroller ports drive the VFD grids and plates. Emulator documentation written from real boards.
- ↑ 5.0 5.1 5.2 Build Your Own Arcade Controls forum, "Coleco Tabletop Galaxian repair", March 2022 (retrieved 2026-10-06). Community thread: a Galaxian with no power; the owner replaced the transistors and the electrolytic and ceramic capacitors and repaired broken tracks, after which faint sound returned but the display stayed dark; no schematic found; unresolved.
- ↑ 6.0 6.1 Coleco Industries, Donkey Kong Instructions and Game Rules, Guide No. 78247, 1982, p. 3 (four C alkaline cells or Perma Power; weak batteries cause erratic display or play) and p. 6 (special information). Hosted here as File:Coleco Donkey Kong Tabletop Instructions Guide 78247.pdf.
- ↑ 7.0 7.1 Coleco Industries, Galaxian Instructions and Game Rules, model 2380, Guide No. 76881, 1981, p. 3 (batteries) and p. 4 (demo mode at switch-on). Hosted here as File:Coleco Galaxian Tabletop Instructions Guide 76881.pdf.
- ↑ Handheld Museum, "Coleco Game Repair", page 1 (retrieved 2026-10-06): opening the case, the speaker cone over the piezo buzzer, and the red and blue battery leads.
- ↑ 9.0 9.1 9.2 9.3 KLOV forums, "Coleco handheld arcade games - anyone fix those or have intel on them?", April–May 2022 (retrieved 2026-10-06). Community thread: a Ms. Pac-Man with one row missing; a Frogger with missing lines fixed by reflowing the display joints.
- ↑ 10.0 10.1 10.2 10.3 Mini-Arcade, "How to fix a handheld game" (retrieved 2026-10-06), repairs 1–3 (dirty contacts) and 4 (speaker wires, with the note that the Coleco tabletops keep the speaker in a baffle). Generic advice for handheld games.
- ↑ Coleco Industries, Frogger Instructions and Game Rules, model 2393, Guide No. 78256C, 1982, p. 5 (no snake at Skill 1 until the first round of homes is filled). Hosted here as File:Coleco Frogger Tabletop Instructions Guide 78256C.pdf.
- ↑ Handheld Museum, "Coleco Donkey Kong" (retrieved 2026-10-06): model 2391, 1982; the joystick-up start.
- ↑ MAME source, hh_melps4.cpp (retrieved 2026-10-06), driver notes for Coleco Frogger: made in Japan, PCB "Coleco Frogger Code No. 01-81543, KS-003282 Japan", Mitsubishi M58846-701P, 600 kHz crystal, Itron CP5090GLR R1B VFD, 12 grid and 16 plate lines.
- ↑ KLOV forums, "Coleco Mini Galaxian Tabletop Repair", August 2022 (retrieved 2026-10-06). Community thread: a Galaxian with no power, voltage present at the board, transformer marked "800"; unresolved.
- ↑ 15.0 15.1 15.2 MAME source, hh_hmcs40.cpp (retrieved 2026-10-06), driver notes for Coleco Pac-Man (PCB "Coleco 75690", Hitachi HD38820A28/A29, Futaba DM-34Z 2A; the A28 version does not show the whole maze at power-on) and Coleco Ms. Pac-Man (PCB "Coleco 911171", Hitachi HD38820A61, Futaba DM-60Z 3I; game selection with the player 1 stick).
- ↑ Coleco Industries, The Official Ms. Pac-Man Instructions and Game Rules, model 2395, Guide No. 91758, 1983: p. 2 (player 1 control stick on the right), p. 3 (demonstration: right stick pushed up), p. 4 (right stick pushed left starts Ms. Pac-Man), p. 6 (right stick pushed down starts Head-to-Head). Hosted here as File:Coleco Ms. Pac-Man Mini-Arcade Instructions 91758.pdf.