Just replaced burnt out bulb in Infocus 4805 projector. Great picture with new bulb but only black and white. Is this a bulb issue or something else in the projector?

Your projector is DLP technology. It employs a "color wheel" to provide colors other than blank/white. That "pop" you heard unfortunately may have been a malfunction of the color wheel mechanism, probably the motor. (It runs at very high RPM)

Sounds like you may have to find a shop to service your projector.

the colorwheel needs to be replaced. the projector won't turn on if the colorwheel motor is not up to speed.

the color wheel has fallen apart and must be replaced. try googling the manufacturer for service.

If you have any video at all and it's only Black and white there is a 99.99% chance that your Color Wheel has lost all of it's glass color filters.
You can confirm this by removing the lamp. then look straight into the projector where the lamp was and you should see the color wheel of colored glass segments (Red, Green and blue) I believe you won't see them because they came off of the wheel.
Also if you lift up the projector and turn it around in various angles and you will hear the small pieces of broken glass from the color wheel.
Unfortunately you will need to take it to an authorized service center for repair. Be prepared to spend upwards of $300 for the repair.

Cheers

first reset to factory settings (menu, settings, factory reset). if problem persists, replace the colorwheel.

reset the settings to factory default.

it there is no high-pitched squeal when it starts up, the colorwheel needs replacing. the lamp won't light without it. the part is under $50, but installation is quite involved.

if the lamp has 2000 hors on it, it needs replacing. go into the menu and find out how many lamp hours are used. it could be the lamp and it could be the ballast.

try buying a new colour wheel

Check your cooling solution wether its a fan malfunction or if it needs a new fan - or h20 cooling system

if not its either the power supply or something serious - send it to manifacture or go to a in-store repair

(it could be the dust protector)