Blue 445 doesn't blank.

[db3306]

Hey folks.
I have a problem with My china projector.
It seems like the blue diode doesn't blank properly.
As soon as the projector is on but is in blackout mode the blue diode is on.
It isnt as bright as when im projecting stuff but its dimmed yet still visible.
I can see the blue when i try to Project only Green and red.

The china company isnt very helpful, all they say is it cant e fixed but im sure it can with the right knowledge or spare part.

Anyone knows what the problem might be?

[LaNeK779]

the blue diode has a "residual" beam that can be visible in dark environment
this is most likely "caused" by a high threshold current, or by the diode driver's design

try to make them tell you which trim pot does what in the blue diode driver . i think you need to find the threshold, or bias pot

on any case, a photo might prove usefull

[db3306]

Thanx for the reply, i guess this could be the answer, would love to try the trim pots but they are all drowned in hot glue

here's a photo of the dot on my hand when the projector is idle.

[allthatwhichis]

What you are seeing is the blue laser driver keeping a lil bit of power going to the diode; this is done for the diode's health as blanking is very hard on a diode and keeping the diode just above lasing threshold while blanking causes less damage than taking all the power from the diode.

Installing a hardware shutter will resolve most of what you are seeing and will make your projector a bit safer.

[db3306]

nice one, thanx for helping

[LaNeK779]

however.... that dot is too bright.... maybe threashold current is set too high, or indeed you have no blanking?
maybe someone else would like to chime in on this. does it scan frames as it should? is blanking working when scanning?

[db3306]

it seems to work when scanning at least its not that obvious when the other modules are running , but it never dims out 100%..

Here's a short video when i had it dimmed 100% in quickshow, in the end of the video i turned it back to normal brightness.

The company i bought it from told me it couldn't be fixed, but im damn sure it can be fixed, i just have to adjust the right thing or change the right part.. But I am not sure which one.

http://youtu.be/w-xoBpu-2JA

They agreed to send me a new blue diode but they didn't think it would solve the problem. So if anyone have any ideas of how to fix it, what part to replace or what pot to adjust i would appreciate it.. I have no idea where to adjust the threshold current or on what board that pot is located.