I have done some experiments with the SVGA signal lines concerning why certain monitors may kill the sound system.
On the SVGA socket pin 11 = Sense 0 pin 12 = Sense 1 pin 4 = Sense 2 pin 15 = Sense 3 The bit pattern of these sense bits indicate the type of monitor is being connected. I found (for the Compaq Presario) that if pin 4 (Sense 2) is not shorted to ground the BIOS will shut off the volume control. This computer originally was packaged with a monitor with integrated speakers and a volume control knob. The older monitors did not use the Sense bits and like my older monitor pin 4 was omitted. I had to insert a small wire into pin 4 on the PC's SVGA socket and run it to the socket's screw terminal to ground the pin. Now I can use an older monitor and still have the volume control working. I hope this will help some in the future with a weird Compaq product. Regards, John K1JEB
