Wd 73c9 screen is very dim

may need the lamp replaced pt# 915B403001
Recommend Phillips, OSRAM or Mitsubishi original (as from experience others will not work or will have very short life)
http://www.shopjimmy.com/dlplamps?tv_brands_select=Mitsubishi&tv_models=Mitsubishi+WD-73C9

may be time to replace the lamp.

I use a very slightly damp cloth with just water. Soap can dull the screen. Wipe lightly. Don't scrub or you could gouge lines. Dry with another cloth immediately.

Here's what the Manual says about light codes for this TV. See Picture of actual page from manual.

The color wheel spins at 10,000 rpm so there's a good chance that the bearings will go out, the heat and burnt on dust that gathers on the lenses and the class panels will be enough to cause mayhem with your color wheel. All the parts inside the light box need to be cleaned at least 1 time a year to keep it working properly. Much care must be taken when doing this it's very easy to destroy the wheel if it falls to the ground it's done. I suggest cleaning it over a carpeted area and keeping it on the floor while working. Place a piece of newspaper down over the carpet to keep fibers out of the area. Anything that gets sealed inside the area after cleaning will be burned onto the lenses and the problems will not be cured.

did u touch the lens or bulbs when u cleaned it? It could be a color wheel problem but i think u should try to reset light tunnel. Did it give you any warning? or did it just all of sudden go dim. I gave u a link to a trusted YOUTUBE tech.. i use his work all the time.
See if any blink codes come up if u disconnect a bulb..good luck
chad man

You need to replace the DLP chip. Get a quote form a TV repair shop.

dim light check first make sure lamp was correct lamp for you model, most time it's worth buying lamp and enclosure to make sure lamp is correct then also it could be ballast problems.

Here's the link to the manual for the WD-73C9.

http://www.mitsubishi-tv.com/pdf/C9-737-837_OG.pdf

Hope this helps you.
Bobya.

check your screen back Light or get a working screen and test it or your screen flax is bad