ViewSonic VG150 won't Display to PowerPC 9600/300 ? ?

A genuine Apple display provides one of about 18 different codes to your Mac at startup. These codes tell your Mac exactly which family of displays is attached. The Mac then limits the range of resolutions allowed so that your genuine Apple display will not be damaged by too high a resolution or refresh rate.

If you are not using a genuine Apple display, you need to do something else, because the default code is "no display connected". The innocent-looking adapter that allows the use of VGA-style [15-pin, three row] monitors with older Mac [15-pin two row] display cards also has a code programmed into it with jumper wires and diodes.

If you are using an adapter that provides the wrong code, you will get messages like "out of range". These messages are not Mac error messages, they are generated directly by your display.

Can this display do 640 by 480?
What other resolutions can it do?
Where did you get the adapter you are using?
Does the adapter you are using have tiny switches?
Do you have a multi-meter?

I think you may have the wrong cable. I have some like vintage Macs (8600/200 and 8100/110AV) hooked to Dell (PC) LCD displays and...
1)Those vintage Macs have Apple's DB15 video connectors - 15 pins in 2 rows.
2)PC displays have VGA HD15 connectors - 15 pins in 3 rows.
3) I have to use an adapter like this:
http://www.griffintechnology.com/products/monitor/

I think it may also be possible that your Mac may have been last used at a higher resolution than the Viewsonic is capable of (1024x768), which may be confusing it. I also have to adjust the timing on the displays to center and stabilize the image.

louie is right. Documents on the viewsonic web site indicate that display has a VGA-style 15-pin three-row connector. The 9600 has a 15-pin two-row connector. These two cannot be plugged together. Unless you modified either the Mac or the display, you should have a small adapter at the Mac end of the display cable. I am suggesting it may not be the right one.

Footnotes under "Mac compatible" indicate that the display ships with a Viewsonic PowerMac adapter. It sounds like you may have substituted any-old-adapter. That is sometimes OK, but not in this case.

The display IS capable of 640 by 480, several other regular Mac resolutions, and a maximum of 1024 by 768.

Two easy ways to try to get it to display a picture are:
• Boot from a CD, which may set it to 640 by 480
• Reset your Mac's PRAM, which may make it revert temporarily to 640 by 480 -- but it will probably change back when the system starts up.