I imagine Nat wired up a cable to the expansion port using this pinout:
Diagram from the back of the PC Engine/TurboGrafx, right side up:
AR GG 01 VM 32 30 27 GG 17 20 22 23 13 11 10 08 GG 05 03 GG VV VN VR
02 CD 35 34 VU 29 26 15 19 21 VJ 14 12 VG 09 07 06 04 24 VT 37 36 VP
AL VV VS 33 31 28 25 16 VL VK QQ VI VH QQ VF VE VD VC VB VA GG VZ VQ
The signals that are important for tapping the stereo audio, NTSC video,
and NTSC RGB signals from the unit are:
AR -- Audio Right
AL -- Audio Left
VZ -- External composite video, connected to R145. Note -- this may need
to be externally bypassed to ground with a capacitor to use directly
as a video feed. Also used as a vertical sync signal for RGB
connections.
GG -- Ground
Credit to the original author goes to: Joseph LoCicero, IV
Basically you hack some AV cables, wire the inner wire for the given channel (L or R audio, and Video) to the exp pin, and the outer shield wiring to ground. The best way to wire up to the exp port is using a connector you can remove, in the event that you get a CD-Rom unit. I heard that old computer ribbon cable makes a nice connector if you can cut to single pins using sharp scissors.
The alternative, build AV ports to your console:
I've never actually seen one of those. I use a homemade A/V wire that a friend made for me.
That's the way to do it. I've made a ton of those over the years. FWIW, I've never seen a Booster in 'real life' either for this precise reason.
Nat, could you share the procedure for making these homemade AV cables?