Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[mixedgas]

I went over to LPF, it looks like the power distribution in the beam has been improved somewhat. It might actually meet the data sheet now. I'm still weary of overdrive. The one I pushed hard did not do so well a year ago and went LED very quickly. At 325$ each, and production limited, we did not push them.

Some place in the world is a really cool new video projector.

Steve

[flecom]

But that feature will not protect you from long term gross overdrive.

I've been running one of the 445 diodes @ 1.2W output in my projector and it has several hundred hours on it already... no sign of degradation

and anyway for the price of these diodes its still cheaper to just replace them

[Xytrell]

Well, they don't die even at 1.9A. They drop in power after 1A or so though, so that means there's no point running them over that

Is it reasonable to say that if they live (even for a minute) at 1.9A, they will live much longer at 900mA?

[steve-o]

IMO apples and oranges. Comparing the c@sio 445 diodes to these mitsu 638s doesn't correlate much ..

[mixedgas]

Well, they don't die even at 1.9A. They drop in power after 1A or so though, so that means there's no point running them over that

Is it reasonable to say that if they live (even for a minute) at 1.9A, they will live much longer at 900mA?

Google Arrhenius and Semiconductior Derating....

Steve

[LaNeK779]

IMO apples and oranges. Comparing the c@sio 445 diodes to these mitsu 638s doesn't correlate much ..

the absence of correlation is a fundamental assumption on all the simpler forms and models of statistical inference
so this is not bad at all

sorry for the off topic, i'm just toasting my mind at work at the moment and all i can think off is this sort of "financial" humour

[steve-o]

lol

__________________

[Solarfire]

The diodes I ordered for testing came today, so here some preliminary info’s on the collimation of these diodes. First of all I did a raw power measurement @ 400mA to see how it meets up to the spec sheet. One diode did 312mW the other 306mW, within specs.

I first tried the 2 cylinder collimation/correction which would normally give the least loss. That it did and showed how much trash there is to deal with. I quickly realized there is not much sense in capturing the whole beam if half of the beam is useless, a lot of power within the fringes of this diode (see pictures). As you can see the first cylinder is a short FL of 3.9mm and its right in the face of the diode, nothing getting clipped there. The lens were not the right FL but close enough to see that this isn’t the way to go.

I then tried an Optima collimator but the lens could not be screwed far enough into the mount to even start thinking of collimating anything. That means the lens is not getting close enough to the diode for reasons whatever, not even without the spring (used Daves mount and one of Edisons Optima lens/Barrel combinations).

I then tried an O-Like which gave some halfway usable results. Output after the O-Like coli was 190mW and after prisms (prisms setup @ Zoofs Brewster angle) 168mW. Divergence after prism correction was @ 1.66mrad. Beam size @ the prism aperture 4.5mm x 1.75mm, farfield 4.5mm x 20mm.

So next up is a test with drlavas cylinders which should give a little better performance with the divergence. Actually a cylinder telescope of about 1:4 – 1:5 would be needed here.

[LaNeK779]

I then tried an Optima collimator but the lens could not be screwed far enough into the mount to even start thinking of collimating anything. That means the lens is not getting close enough to the diode for reasons whatever, not even without the spring (used Daves mount and one of Edisons Optima lens/Barrel combinations).

i am not getting this Frank, is it the mount to blame or the lens/retainer? i also have edison's optima lens and barrel and the lens sits at the bottom of the barrel. this, combined with dave's mounts can get the lens as close to the diode as possible. maybe try with one of dave's lens barrels?

i hope you mean an issue with the particular mount and not decaning the diode to get closer to the emmiter...


so in general, we are talking about 1.5-1.6 divergence with 35% loses for the best farfield so far (o-like and prisms)

[Solarfire]

i am not getting this Frank, is it the mount to blame or the lens/retainer? i also have edison's optima lens and barrel and the lens sits at the bottom of the barrel. this, combined with dave's mounts can get the lens as close to the diode as possible. maybe try with one of dave's lens barrels?

i hope you mean an issue with the particular mount and not decaning the diode to get closer to the emmiter...

OK.. another update. I got the Optima lens working, there was some grating where the adjustment slit starts, that kept the barrel from going further into the mount.

Well that didn’t really make things better. The loss is down; we are getting 294mW after the collimator and 260mW after the prisms. Divergence is up to 8.57mrad after the collimator, beam size @ the aperture 4mm x 0.8mm and far field @ 11m 4.5mm x 95mm. After the prisms we have a divergence of 3.5mrad, beam size @ the aperture 4mm x 1.5mm and far field @ 11m 4.5 x 40mm.

Note that the prism angles are kept at a max of Brewster’s angle, greater magnifications should be done with cylinders!