NEO-CDA board

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=

Carries a 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=



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 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.



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.