La MASA la tienes en la propia carcasa del Euroconector (( pin 21 )) e incluso en las mallas de los pin's de sonido.
No obstante, te pongo la descriccion de cada pin del Euroconector:
Pins Euroconesctor
01 AOR Audio Out Right 0.5 V rms <1k ohm
02 AIR Audio In Right 0.5 V rms >10k ohm
03 AOL Audio Out Left + Mono 0.5 V rms <1k ohm
04 AGND Audio Ground
05 B GND RGB Blue Ground
06 AIL Audio In Left + Mono 0.5 V rms >10k ohm
07 B RGB Blue In 0.7 V 75 ohm
08 SWTCH Audio/RGB switch / 16:9
09 G GND RGB Green Ground
10 CLKOUT Data 2: Clockpulse Out (Unavailable ??)
11 G RGB Green In 0.7 V 75 ohm
12 DATA Data 1: Data Out (Unavailable ??)
13 R GND RGB Red Ground
14 DATAGND Data Ground
15 R RGB Red In / Chrominance 0.7 V (Chrom.: 0.3 V burst) 75 ohm
16 BLNK Blanking Signal 1-3 V=RGB, 0-0.4 V=Composite 75 ohm
17 VGND Composite Video Ground
18 BLNKGND Blanking Signal Ground
19 VOUT Composite Video Out 1 V 75 ohm
20 VIN Composite Video In / Luminance 1 V 75 ohm
21 SHIELD Ground/Shield (Chassis)
. 