Identify a system, not just a shell
The Sega CD is the CD expansion for a compatible Genesis; Mega-CD is the name used for other regional versions. Treat the console and expansion as a matched system. Record the model label of each piece, the region printed on the game packaging, and any BIOS or video modifications disclosed by the seller. A working disc demonstration is more useful than a photograph of a power light. Integrated CDX or Multi-Mega machines need their own service documentation and should not be treated as two separately replaceable boxes.
Begin with the existing Sega CD model differences article for the front-loading and top-loading families. On a top-loading unit, identify the actual board and mechanism before ordering drive parts. Sega issued a revision-specific service supplement; even component layouts changed. That is evidence against assuming every Model 2 has identical internals. Sega CD II service supplement.
Ask for a useful demonstration
- Show the base Genesis running a known working cartridge with the CD unit detached. This establishes a starting point for the display, controller and console.
- Show the assembled CD system reaching its boot screen and loading an original disc from a cold start.
- Show gameplay that reads another area of the disc, with both game audio and music audible. A title screen alone cannot establish sustained reading.
- Show the tray opening and closing on a front loader, or the lid and spindle clamp on a top loader.
- Show the memory manager without formatting existing storage, plus a saved game loading if the owner has one.
Inventory what is included
List the two power supplies separately, including their labels, rather than accepting “Sega adapter included.” Inventory the mounting parts, any model-specific extension support, audio mixing cable where the chosen setup needs one, video cable, controllers and expansion-port cover. Consult the matching original Model 2 user's guide diagrams. Missing mechanical supports can leave the assembly unstable; missing cables can hide a functional system behind an apparent audio fault.
Evaluate repair claims
“Recapped” describes work, not a successful test. Ask for the board revision, parts used, photographs of soldering, and before-and-after symptoms. “New laser” also needs a mechanism identifier and a test with several discs. A unit that reads audio but fails a game is not automatically ready for daily use. Price a nonworking unit as an unknown repair until its symptoms are documented.
Photograph serial labels and exterior damage when the package arrives, then perform the same demonstration before changing anything. Keep packing pressure away from the lid or tray, and retain the seller's test video. The useful purchase record is a complete hardware inventory and repeatable behavior, not an unsupported claim that one model is always reliable. Continue with power and setup before the first assembly.