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PC Engine CD-ROM² / Duo

The CD-ROM add-on for the PC Engine (1988), evolved into Super CD-ROM² then integrated into the Duo (1991, Duo-R, Duo-RX). THE preservation nightmare: the SMD capacitors that leak and corrode — recap almost mandatory. The modern solution: the Super SD System 3 ODE.

PC Engine CD-ROM² / Duo board
PC Engine CD-ROM² / Duo board. Photo: Evan-Amos, public domain.

Identification

Field Value
Manufacturer NEC / Hudson
Releases CD-ROM² (1988) · Super CD-ROM² (1991) · Duo (1991)
Type CD add-on (or Duo = all-in-one)
Media CD-ROM + System Card (CD BIOS on a HuCard)

Architecture (the CD addition)

The CPU/video stay those of the PC Engine (HuC6280 + HuC6270/60). The CD add-on brings:

Block Element Notes
Sound decoder ADPCM (Oki-like) plays compressed CD voice/music
Buffer RAM 64 KB (CD-ROM²) → 256 KB + 2 KB (Super CD-ROM²) the System Card defines the available RAM/BIOS
BIOS System Card (HuCard) v1/v2/v3; Super System Card (v3) required for "Super CD-ROM²" games
Save battery-backed internal RAM (BRAM) shared saves

The generation (CD-ROM² vs Super CD-ROM² vs Arcade Card) is distinguished by the amount of RAM the system card unlocks — a key compatibility criterion.

The Arcade Card (the top tier)

The Arcade Card adds 2 MB of extra RAM, essential for the big SNK/Neo-Geo arcade ports (Fatal Fury, Art of Fighting, World Heroes). Two forms: Arcade Card Duo (for the Duo/Super CD-ROM²) and Arcade Card Pro (also includes the Super BIOS, for a plain CD-ROM²). It's the highest tier of the PC Engine CD compatibility stack.

⚠️ Recap — almost mandatory

The Duo/CD capacitors leak and eat the traces

The electrolytic SMDs in the CD units (especially Duo / Duo-R) leak systematically → no more sound, no CD reading, trace corrosion. Recap imperative on purchase, + electrolyte cleaning and repair of the affected traces. Per-CXX list: see Console5.

Common faults

Symptom Likely cause Lead
No sound / no CD boot Leaked capacitors + traces Recap + trace repair
Won't read CDs Worn / misaligned laser Adjust/replace, or ODE
System Card not read HuCard contacts Cleaning
Visible corrosion Cap leak Neutralise, recap, jumper the traces

Mods & preservation — what to buy, how

  • Super SD System 3 (Terraonion) 🟢: the flagship mod. Plugs into the expansion bus and replaces CD + System Card BIOS + RAM with SD storage — no laser, CD games loaded from the card, built-in BIOS. No soldering (external module). → Super SD System 3 page.
  • Recap: a mandatory prerequisite before anything (see the Recap section above) — the Duo/CD SMD caps leak.
  • RGB: clean output goes through the host PC Engine (RGB mod per model) → see PC Engine page.

Photos / assets

(To add: Duo, caps/corrosion area, laser block, System Card.)

Advanced repair

SMD recap all but mandatory (electrolyte leakage = the No. 1 issue, especially Duo/CD) + laser/optics. Methods: Recap · ODE (optical drive) · Traces & vias.

Sources & attribution

Image:

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

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