NEO-CDA board

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The audio/video and power boards in top-loading NeoGeo CD consoles.

The version for the front-loading console is CD-ANA-2.

NEO-CDA3-1

Neocda31.jpg

Carries a YM3016 DAC, LC78815 CDDA DAC, 2 quad op-amps, a CXA1645 video encoder, 2 7805 regulators, a LM2930 8V regulator and various transistors.

Connectors, from left to right (need exact pinouts):

  • YM2610 to YM3016 serial data
  • CDDA left, right, clock
  • RGB video and sync
  • CD 5V, 10V CD, 5V logic, Ground

NEO-CDA4-1

Neocda41.jpg

Same as the NEO-CDA3-1, but with only one dual op-amp and a second LC78815 instead of the YM3016 (which isn't needed anymore with boards using the NEO-YSA chip, capable of outputting LC78815-compatible data).

24M08 regulator instead of the LM2930 ?

Connectors, from left to right (need exact pinouts):

  • CDDA left, right, clock
  • NEO-YSA left, right, clock
  • RGB video and sync
  • CD 5V, 10V CD, 5V logic, Ground

Power supply circuit

Circuits for both versions of the board seem to be identical.

Neo-cda3-1.png

Both +5V and +10V supply voltages are limited to 5V and 11.4V by means of a pair of (strange) protection circuits made of transistors to bring the voltage down by dissipating heat through resistors R15 and R18 if needed. The +5V input is used to power the main board. The +10V input is used to power the CD drive, and 3 linear regulators for the op-amps and audio DACs.

A thermal fuse (one-time use ?) is coupled to Q3 with a blob of silicone, preventing the console from being turned on again if excessive heat was generated.