ColecoVision Expansion Module 3 Troubleshooting Guide
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Fault-finding for the ColecoVision Expansion Module 3, the Adam computer attached to a ColecoVision. The memory console, keyboard, data drives and printer, with the power supply in the printer, are the complete Adam's units, and Coleco's check-out procedure, the supply rail figures and the printer and data drive faults are on Coleco Adam Troubleshooting Guide. The checks below are the ones that apply to Expansion Module #3 because the ColecoVision does the work of the Adam's CPU board and drives the TV.[1] Care and set-up are on ColecoVision Expansion Module 3 General Maintenance.
Before you start
[edit | edit source]Coleco's check-out guide has three points that apply only to Expansion Module #3:[2]
- The ColecoVision's own power supply must not be plugged in, and the ColecoVision's ON/OFF switch must be off. The system is switched on at the printer.
- The cable from the antenna switch box goes to the ColecoVision, not to the memory console.
- Any Expansion Module #1 must be switched off and removed.
Then run Coleco's power-on check as described on Coleco Adam Troubleshooting Guide: with no data pack and no cartridge, the keyboard's red light comes on, the printer hums and its mechanism moves, and the TV shows the SmartWRITER typewriter screen.[2]
Symptom checklist
[edit | edit source]| Symptom | Likely cause | Check |
|---|---|---|
| Nothing at all: no keyboard light, no printer movement | Printer supply, mains, printer cable | As for the complete Adam: If nothing comes on and the supply rails |
| Printer and keyboard light work, no picture on the TV | Switch box cable on the memory console instead of the ColecoVision; channel switch on the back of the ColecoVision not set to the TV's channel; an Expansion Module #1 still fitted | Coleco's check-out guide, p. 4. Then the ColecoVision's own RF stage: ColecoVision Troubleshooting Guide |
| Picture present but scrambled, or wrong colours | The video circuits are the ColecoVision's: video processor, video RAM, colour clock | ColecoVision Troubleshooting Guide, with the console attached to the memory console as usual |
| No picture on a monitor | Not a fault: Expansion Module #3 has no composite video output | Use a TV through the switch box |
| Adam does not start, or starts with a garbled screen, after the consoles were separated | Edge connector between the consoles not seated or dirty; a ribbon cable damaged; a buffer on the interconnect board | Reseat and inspect. Check +5 V at pin 20 against pin 10 of U1 to U4 on the interconnect board |
| ColecoVision dead with the Adam powered | A rail missing at the ColecoVision's expansion connector | Measure +5 V (pins 58, 59), +12 V (pin 57) and −5 V (pin 60) against ground (pins 1, 2) at the interconnect board's edge connection |
| A game cartridge stopped working after being changed with the power on | Damage from inserting it while the computer was on | CBS warns that this can cause permanent damage. Test the cartridge in a ColecoVision on its own supply |
| Roller Controller will not connect | The console's power socket is not available with Expansion Module #3 | Coleco's ADAM adapter; see ColecoVision Roller Controller General Maintenance |
Sources: Coleco's check-out guide,[2] the Technical Reference Manual,[1] the interconnect board drawing[3] and the CBS manual.[4] Wikipedia records the Roller Controller's power connector problem.[5]
The interconnect board
[edit | edit source]
The interconnect board joins the Adam memory and I/O board to the ColecoVision's expansion port. Many lines pass straight through; the Z80's address and control lines are buffered, and the data lines are buffered in both directions under control of the ColecoVision's RD signal and the 245EN line.[1]
| Part | Type | Lines |
|---|---|---|
| U1 | 74LS245 | Data bus D0-D7 |
| U2 | 74LS541 | A0, A14, M1, MREQ, RFSH, IORQ, WR, RD |
| U3 | 74LS541 | A1-A4, A13, A15 |
| U4 | 74LS541 | A5-A12 |
| C2 | 10 µF tantalum | +5 V to ground |
| C3-C6 | 0.01 µF | Supply decoupling at U1-U4 |
Source: drawing 41840 revision F.[3]
The buffers sit between the Z80 in the ColecoVision and the Adam's memory and I/O board,[1] so a buffer fault can leave the printer and keyboard light working while the Adam itself does not start. With the system on, check each chip's supply at pin 20 against pin 10, then look for activity on its inputs and outputs with a logic probe or oscilloscope.[3]
Related pages
[edit | edit source]- ColecoVision Expansion Module 3
- ColecoVision Expansion Module 3 General Maintenance
- ColecoVision Expansion Module 3 Capacitor Replacement Guide
- Coleco Adam Troubleshooting Guide
- ColecoVision Troubleshooting Guide
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Coleco Industries, ADAM Technical Reference Manual, Preliminary Release, section 2.4, "Differences of Expansion Module #3" (PDF pp. 41-42): the equivalent of the CPU board housed in the ColecoVision; no composite video output, so no monitor; the ColecoVision board and the memory and I/O board joined by two 30-pin ribbon cables, a dual 30-pin card edge connector and the interconnect board; A0-A15 buffered with tristate control from the memory and I/O board; D0-D7 buffered both ways, direction set by the ColecoVision's RD and the tristate by 245EN; M1, MREQ, RFSH, WR and RD buffered. Hosted here as File:Coleco Adam Technical Reference Manual (Preliminary Release).pdf.
- ↑ 2.0 2.1 2.2 Coleco Industries, ADAM System Check-Out and Trouble-Shooting Guide, code 42464E, 1983: step 1 of the check-out, p. 2; "if the computer does not come on", p. 3 (for Expansion Module #3 owners, the ColecoVision power supply not plugged in and the ColecoVision ON/OFF switch off); "if you do not see this picture", p. 4 (with Expansion Module #3 the switch box cable runs to the ColecoVision console; the channel switch on the back of the memory console or ColecoVision; disconnect Expansion Module #1 if present). Hosted here as File:Coleco Adam System Check-Out and Trouble-Shooting Guide 42464E.pdf.
- ↑ 3.0 3.1 3.2 Coleco Industries, Schematic, interconnect P.C. board with buffers, drawing 41840 revision F, 14 June 1983, "used on 2404": U1 74LS245 on D0-D7; U2 74LS541 on A0, A14, M1, MREQ, RFSH, IORQ, WR and RD; U3 74LS541 on A1-A4, A13 and A15; U4 74LS541 on A5-A12; supply on pin 20 and ground on pin 10 of each chip; the edge connection with +12 V on pin 57, −5 V on pin 60, +5 V on pins 58 and 59 and ground on pins 1 and 2; C2 10 µF tantalum across +5 V; C3-C6 0.01 µF. Sheet 4 of File:Coleco Adam Schematics.pdf; also File:Coleco Adam interconnect board schematic 41840 Rev F.png. Revision E is appendix 4.3 of the Technical Reference Manual.
- ↑ CBS Electronics, CBS ADAM The Complete Computer System Owners Manual (UK), © 1984, p. 8: game cartridges should not be inserted when the computer is on, or permanent damage may result. Hosted here as File:CBS ADAM Owners Manual (UK).pdf.
- ↑ Wikipedia, "ColecoVision" (retrieved 2026-10-19), used for history only: the Roller Controller's power connector not compatible with Expansion Module #3, and Coleco mailing an adapter to owners who complained.