Man ... There is no pin on it to disable the SoG. That I can say for sure. There's also no RAMDAC inside the newer GS chips so there's no analog RGB on the mobo, exeption being the RGB which the CXM chip outputs.
I suppose the SOG on/off switch is now probably controlled by software. (there's a I2C bus on the CXM chip which is connected to the HDD interface chip, the CXD9611 on the GH-023 mobo. On the GH-026 mobo the HDD chip and sound chip merged into one bigger chip.)
PM me if you want more details
SCPH-10000_GH-001 SCPH-15000_GH-003 SCPH-18000_GH-008 SCPH-30001_GH-005 SCPH-30000_GH-016(V4) SCPH-30001_GH-010(V4)
2xSCPH-10190, 2xSCPH-10350, 2xSCPH-10280
"**** j0 hackers!"
-Sjeep (As seen on TOXIC OS ELF...)