I also need it for a project of my on the BLACKSTAR 60W electric guitarIt has to be a standard old fashioned filament type bulb, not an energy saver, and of a voltage that is similar to your home supply.
Wattage is typically 60w or 100w depending. For a low current project or testing a power supply off load then an even smaller wattage may be more appropriate.
what mod did you do?
and for what purpose?
looks like you changed a bunch of diodes and transistors.from what i can see in the picture it looks like the original output transistors have been replaced with metal tab types (hope you have the right insulating hardware in place)