I have a JVC
HD-70FH97. I have had it for six or seven years.
Recently I have noticed dark patches just left of top-center that run roughly diagonally down the full height of the screen. I replaced the bulb but the patches are still there. I found a dialog that you had with another customer and surmised that I have contamination on my projection lens and or mirror.
I removed the lamp and cleaned the optical iris. That had no effect on the dark patches. I unplugged the unit and waited for it to cool, then used a can of compressed air to blow out the intake and exhaust ports. That made the picture even worse. I believe instead of blowing the dust out, I blew it back into the unit and further contaminated the lens/mirror because I now see a splatter pattern of small spots that resemble rain/water drops on glass.
I procured a service manual for the unit, but am somewhat daunted by the instructions for gaining access to the components, i.e., removing the back cover. Is there a "path of least resistance" for accessing and cleaning the projection lens and mirror? That is, can I remove the back cover without removing the mirror, and clean the mirror "in place"?
PS - There are no authorized repair shops near me, and the unit is no longer under warranty. So, I am going to try this myself.