I am trying to install a Sonnet Encore/ST G4 1.4 processor. I have installed the firmware patch and done everything else the manual recommends. I do not have an install disc. I replace the processor and the machine tries to boot but the monitor goes off. Any suggestions? Can I download an install CD?

SOURCE: Computer shut down message after installing Encore upgrade.

I'm not a Mac expert but I did find your Mac went through 4 design changes.  What is the model number of your Mac?  This is important because not all models are upgradeable per another website.

  Quote:

Is the CPU on the Power Macintosh G4 upgradable? How is it mounted?

Officially, Apple does not specify that the processor on the Power Macintosh G4 series is upgradable, since Apple has no plans to offer upgrade cards for the machines. However, PCI-based Power Macintosh G4 models have the processor mounted on a ZIF, and AGP-based Power Macintosh G4 models have the processor mounted on a daughtercard with a 300-pin connector.

To determine whether your Power Macintosh G4 is PCI-based or AGP-based please refer to the specifications for the particular model of interest, and to the Technical & Performance Q & A section of this Q & A.

Also in my research I found references that the "firmware" may also need updating.  But that may apply to a different situation.
   

SOURCE: I need manual for Sonnet

try it in the manufacture website.

SOURCE: Digital Audio G4 Mac with a Sonnet Encore ST G4 1.4 GHz

reinstall it.