In spirit of broadening my horizons (as well as lack of interesting PC parts to fix) I bought a W10000 projector, which is fully working. Soon after I saw a similar projector, Benq PE7700, with bad colors, which interestingly also uses the exact same bulb as the W10000. Since original bulbs are hard to come by at this point I decided to grab also this one. Worst case scenario (EPIC FORESHADOWING) I still have a pretty good lamp.
Pretty good set of inputs for a 2007, eh?
So far so good, color wheel isn’t discoloured or physically broken, so let’s clean it using compressed air and see what’s going to happen.
Yep, still bad colors. Service menu allows me to change “Color wheel delay”, which should fix the banding issue.
There is one, small, even tiny problem.
This setting does absolutely nothing.
OK, so let’s take it apart some more.
I have to say that this thing is built like an onion. So many layers to peel before You get to the good stuff.
Anyway I got my hands on the color wheel itself, oiled it and mid doing that I got an idea.
Remember the pattern it displayed? It was almost like it was offset by one “part” of the CW, or 60 degrees. What If I swapped the marks for the photodiode?
After reassembly that’s what I saw:
Way better picture, different banding and colors were still not correct – and no, swapping the mark 60 degrees but in the opposite direction did not help, it was exactly the same.
Using oscilloscope I checked the cwspeed signal and it showed me perfect 150Hz signal, perfect 2.5x the 60Hz input signal that manual calls for.
I checked the opamp, this is an invering opamp circuit with 2V offset and 51x gain, which means that it should pull the CWINDEX to ground when CWSPEED is high. And that’s exactly what I saw.
I also tried changing the color wheel speed from 6x to 4x in the service menu while measuring MTRPWM singal, which I think drives the BLDC driver, but PWM did not even budge.
Now here’s the real problem:
MTRPWM comes from the DDP1010 processor and is derived from the CWINDEX, which likely means that the DDP IC is broken. Moreover, it doesn’t send any signal to the DMD chip when blanking of any color is selected in the service menu. I can’t realistically proceed without changing this chip and due to its price it’s completely not worth it, so this unit will become a parts donor – it very likely has a good color wheel, DMD chip and most importantly a working original lamp.
Thanks for reading!