doug
Site Admin
Joined: 08 Sep 2005
Posts: 361
Location: Bristol
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 Posted: Tue Sep 22, 2009 7:16 pm Post subject: Fixing the colour wheel on a PTD3500E |
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I hadn't fixed any projectors for a while but after seeing this beast come up cheap i immediately drove 100 miles to pick it up!
3500 Lumens with 2 spares lamps  The catch was neither of them worked. This immediately made me think the lamps were fine and there was some other problem causing the lamp light to come on..i suspected the ballast.
Strangely enough i couldn't find any logic signals attempting to turn the ballast on..so i applyed my own and the lamp fired up no problem!
I thought that perhaps it was a logic error but all seemed to be working fine. This thing even had an embedded computer to control the LAN interface. I didn't know the IP so i did a ping sweep and found it. Then i didn't know the password so i tried the default one and bingo!
And very helpfully i found an onboard diagnostic utility which said the colour wheel wasn't working! This made sense..if it wasn't spinning up the projector could hold back the lamp.
Hidden deeply inside the projector i found the colour wheel..
I took it out and it appeared fine..but i found a small piece of insulating tape cut carefully into a rectangle. I looked up the IC on the wheel which turned out to be an IR sensor. I figured this was responsible for syncing the colour with the DLP chipset. But how did it work when the surface it was beaming IR onto was shiny and uniform? This is when i realised that the small bit of tape could be the marker on the colour wheel I stuck back a replacement with a tiny bit of epoxy to make sure it didn't come off again..but also being careful not to unbalance it.
Then i put it all back and fired it up..all was going well so far!
But then i got an image with the colours all messed up. This made sense..because i couldn't tell where the tape was originally the chipset wasn't synced to the wheel properly and was flashing the wrong colour up for the image on the DLP chip.
I figured that when they make these things they probably don't mess about trying to stick the marker in exactly the right place so i assumed there must be some way of calibrating it.
I eventually found the service manual which i had to pay for and as i suspected there was a section on syncing the colour wheel! This completely solved the problem and the projector worked perfeclty I didn't have a screen setup at the time so you'll have to believe me!
The above shot shows the DLP chip after removing the lense. This is really nice projector, very well engineered but let down by a piece of insulating tape! |
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