No picture good sound good lamp can change channel

you may have a bad ballast that produces the voltage for the bulb.

Would you be able to provide the model number of your TV to provide you with more info?
If your TV is a DLP, the lamp would need to be replace to get the picture working again.

Yes.Depend how old is ur DLP tv,the Projection Lamp only a light source,mostly depended on the Light projection Engine itself.Get the original RCA DLP lamp or same lamp model now inside the tv,will help and work best for ur tv.Just don't get generic DLP tvs lamp,it cheaper poorer quality.

Here is th elink to Philips support page fro your TV.
Turn on the TV, if it is working you should see the light of the back light lamp. If you are changing channels and hear audio from different channels it is a good bet you lamp is open.
http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?ctn=60PP9202/17&slg=en&scy=US

my philips projection tv model number 50pl9126d/37 has a dark screen

replace light bulb,
if you are hearing a click like the stove is because the lamp balast is trying to power on the lamp,
if you need part number and vendor please send me the model number

Check that when you turn on the TV the Lamp is striking (turning on).

My thoughts are that you will have to reset the lamp hours counter to make it work, as the TV does not know that you have replaced the lamp. To do this, check the leaflet that comes with the lamp - it should explain how to reset the counter for the lamp hours.

No reset button, you may have a bad lamp. Look in you owners manual and which light is flashing it will tell you if the lamp is a possibility.

The color wheel isn't spinning.

IF you would like help diagnosing your set. Go to the enclosed link. They have the service manual for your set and offer unlimited chat support for only 29.99. Just click on your sets manufacturer and you will see your model. Then click on the contact us link and provide your email address and they will email your manual and instructions on how to obtain your support. I am one of their techs. This manual contains step by step procedure for troubleshooting Your RCA DLP Light Engine
http://servicemanuals.vstore.ca/