Daewoo CPC-400 General Maintenance
The Daewoo CPC-400 (X-II) is a Korean MSX2 desktop from 1987 with a built-in power supply, one or two floppy drives and a separate keyboard.[1] No Daewoo service manual for it has surfaced. The notes below come from Daewoo's Korean user manual (Daewoo CPC-400 User Manual), the MSX Resource Center and RBSC's 2026 work on CPC-400 and 400S boards.
The clock cells
[edit | edit source]The clock is backed up by AA cells in a holder on the video board, which sits above the main board on cables. RBSC found that the cells on every board it received had leaked, destroying video boards and running down the cables to corrode the main board, so that cables, the battery holder, IC sockets and connectors had to be replaced.[2] Daewoo's manual says that a wrong time or date means the cells are exhausted.[3]
- Open the case and find the cell holder on the video board.
- Remove the cells at once if they are still fitted, whatever their state.
- Inspect the holder, the video board under it, the cables to the main board and the main board below for white or green deposits.
- Clean any leakage as described in Battery Explosion, Capacitor or Corrosion Damage. Replace connectors and IC sockets that have corroded, as RBSC had to.
Fit fresh cells only if you want the clock, and take them out again if the machine will be stored.
Mains supply
[edit | edit source]- The rear voltage selector has 100 V and 220 V positions and is set to 220 V at the factory. Set it to match the supply before switching on.[4]
- The fuse is on the rear panel.[4] The manual does not give its rating; read it from the fuse fitted and replace it like for like.
- The two outlets on the back carry the incoming mains for a monitor and another device.[4][1] They are live whenever the machine is plugged in.
Warning: the supply inside the case, the voltage selector and the auxiliary outlets carry mains voltage. Unplug the machine before opening it, and treat the supply's capacitors as charged until you have measured them.
Measuring the supply
[edit | edit source]Measure the rails at the cartridge slot.[5]
| Pin | Signal |
|---|---|
| 41, 43 | Ground |
| 45, 47 | +5 V |
| 48 | +12 V |
| 50 | −12 V |
No tolerance is published for the CPC-400.
Floppy drives
[edit | edit source]The CPC-400 has one or two 720 KB 3.5-inch drives, run by a WD1772 controller on the main board.[1][6] Daewoo's manual tells owners to ask a dealer to fit a second drive.[7] For cleaning the heads and the mechanism, see Floppy Drive Repair.
Keyboard and front panel
[edit | edit source]The keyboard plugs into a socket on the front, and the light pen and joystick sockets are behind a hinged door on the front.[7] Check the keyboard cable and plug before suspecting the keyboard itself.
Capacitors
[edit | edit source]What is known of the CPC-400's capacitors is in the Daewoo CPC-400 Capacitor Replacement Guide. Advice on the MSX Resource Center forum is to replace the main supply's capacitors whatever their condition.[8]
Related pages
[edit | edit source]- Daewoo CPC-400
- Daewoo CPC-400 Troubleshooting Guide
- Daewoo CPC-400 Capacitor Replacement Guide
- Daewoo CPC-400 User Manual
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 Daewoo CPC-400, MSX Resource Center wiki, 20 June 2026—link(accessed 2026-10-21) Korean MSX2 from 1987; separate keyboard; power supply built in; one or two 720 KB 3.5-inch drives; power plug for AC 220 V ±10 %, 60 Hz and two outlets for a monitor and another device; many CPC-400 and 400S machines not fully tested before sale.
- ↑ Daewoo CPC-400/400S MSX2/MSX2+ Conversion Project, RBSC, 2026—link(accessed 2026-10-21) Project description (Docs/Daewoo_CPC400_Upgrade_Project_English.pdf, pages 3 and 4): removable AA clock cells on the video board above the main board; leaking cells destroyed video boards and corroded main boards through the cables; all the boards received were badly corroded; one video board needed cleaning, resoldering and additional capacitors; cables, battery holder, IC sockets and connectors replaced and green-stained pins cleaned; on the board used, an unstable crystal oscillator, at least two faulty 74LS367 buffers and a 74LS157 that stopped the clock IC holding data; the schematic lists some capacitor values incorrectly; on the 400S the master oscillator is on the video board, on the 400 on the main board.
- ↑ Daewoo, X-II (CPC-400/400S) user manual, printed page 30: the clock is backed up by dry cells and keeps running with the power off; if the time or date is wrong the cells are exhausted and should be replaced. See Daewoo CPC-400 User Manual.
- ↑ 4.0 4.1 4.2 Daewoo, X-II (CPC-400/400S) user manual, printed pages 5 and 12: rear power selector switch for 100 V or 220 V, set to 220 V at first; set it to 100 V before use on 100 V; auxiliary power outlets supply the incoming mains; a fuse on the rear panel blows to protect the computer from excessive current; the power switch is at the bottom right of the front. See Daewoo CPC-400 User Manual.
- ↑ Daewoo, X-II (CPC-400/400S) user manual, printed page 235, cartridge slot pins: 41 and 43 GND, 42 clock (3.579545 MHz), 44 and 46 SW1 and SW2, 45 and 47 +5 V, 48 +12 V, 49 sound input, 50 −12 V. See Daewoo CPC-400 User Manual.
- ↑ Photograph of the CPC-400 main board, uploaded to the MSX Resource Center wiki by Gdx on 28 June 2016 (File:Daewoo CPC-400 main board.jpg): DW64MX1, Goldstar Z8400A, AY-3-8910A, WD1772-PH floppy disk controller.
- ↑ 7.0 7.1 Daewoo, X-II (CPC-400/400S) user manual, printed page 4: front panel parts, including drive A with its lamp and eject button; to add another disk drive, consult a specialist shop or service centre. See Daewoo CPC-400 User Manual.
- ↑ Recap recommendations, June 2018—link(accessed 2026-10-21) Reply by RetroTechie, 23 June 2018: main power supply capacitors in an MSX are worth replacing whatever their condition; audio and video capacitors show their condition in the output; bypass capacitors round the board can often be removed without the machine stopping.