Here is the info for the tg16 expansion out
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
VR -- Blue RGB signal
VP -- Green RGB signal
VQ -- Red RGB signal
VN -- Horizontal sync signal
To connect the PCE or Turbo to a standard television set or VCR, use the
following pin connections:
AR and GG \ Connect these to RCA cables, ground going to the "shield" or
-- outer metal wrapping, and AR or AL going to the "signal" or
AL and GG / center pin. These plug directly into your Audio In R/L on your
TV or VCR.
VZ and GG -- Similarly, connect GG to the "shield" and VZ to the "signal" of
an RCA cable. This connects to the Video In on your TV or VCR.
For a clearer picture, connect a 0.1 uF capacitor between the
two terminals on the side of the cable that connects to the
PCE/Turbo.
VR/VP/VQ/VN -- If you have an older RGB monitor capable of horizontal sync at
NTSC frequencies (around 15 kHz), you can use it as a monitor
for your PCE/Turbo. Connect VR, VP, and VQ to the blue,
green, and red inputs of the monitor. Connect VN to the
horizontal sync input, and VZ to the vertical sync input. If
the monitor only has a single sync input, use VZ. You should
have an incredibly clear, crisp picture!
NOTE -- Most modern monitors will *NOT* sync this slowly.
Monitors of the "Sony Multisync" variety of old (e.g. the
"2A") are capable of syncing to these frequencies. Also,
monitors marked as "Amiga Compatible" should sync to the NTSC
frequency as well.