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

[CDBEAM]

Kiy...The only other adjustable mount I have used is Daves from LSP. It is a very simple, straight forward design...that does work. It is a matter of the ease of adjustment. The LDADM V7C is easy to dial in the x-Y...just slowly rotate the positioners. With the LPS mount...the tension on the four (4) back plate bolts must be just right to allow for adjustment....but not let gravity pull the plate back out of the adjustment for the X direction. For the Y direction...again...it is a matter of ..." a little this way....then that way....and then back this way "

Is the extra cost/time to machine "worth" that ease of adjustment ??? Dunno ??? A matter of personal opinion !!

I remain of the opinion that some extra mass close to the LD location can act as a "thermal flywheel"...absorbing excess heat when the LD is driven at 100%...and radiating that heat away from the diode in a slightly more efficient fashion. The LDADM V7 has that extra mass. Again....is this a worthwhile feature as viewed against the extra cost and slightly larger footprint ???? Dunno ??? A matter of personal opinion !!

Sorry I have NO black and white answer. I DO feel that a adjusable LD mount is desireable... how one acheives that adjustable feature is the basic question...BEAM

[kiyoukan]

Well the problem im working with is the idea if there is a NEED to use these with the short FL lenses.
Or would the better solution be tight tolerances on the lens threads.
If you make them within a 0.006mm tolerance the play would be almost nothing and be very very tight.
It seems there is no performance reason, based on your data.
Nothing over what a good quick wrap with Teflon tape cant fix.
As it is i did some testing with different materials to coat threads from paint to plastic the results were just a bit more stable (lens not bouncing) but no power loss or gain.

[dave]

Not sure that a tighter tolerance would be the solution as the output angle of one diode will be different to the next ( I think variation is around 5% IIRC)

[steve-o]

Wow 5% variation from diode to diode? Didn't know that. That's kind of bad.

[planters]

kiyoukan,

I like the tape. Once you get the clearance compensated by a given length of tape, it remains pretty consistent from lens thread to lens thread. And, you can remove the tape without much fuss and little mess.

If the emitters on the 71's and the 73's are the same size then the next question is, are their thresholds the same? If so, then the intercavity intensity for each should be similar at the same drive current. So, they should both have approximately the same maximum power output unless the leads for the 73's are thicker or there are more of them. Are they different? I remember DTR running the 71 up to 1.7A. Do we know this is excessive or that it is less excessive if the 73's are run at this current?

[kiyoukan]

Well something to think about here.
Look at the heat we get out of the 445nm diodes, vs the heat from these 635nm diodes.
We are seeing that the max power is kinda based off the thermal stability of the emitter and in some cases is limited by the thermal property's of the package the emitter is attached to.
From the testing i think the 750ma i recommended is on the low side, after seeing people push the limits and the temp at those currents i think these diodes can be driven harder.
I am happy with 2 diodes doing 1W but i know i could up the current to get them doing 1.5W with long life and still less heat than the 445nm diodes.
Now i know this is not a 100% right comparison due to the obvious reasons they may not be built to take the same kind of beating but its sure looking like it.
No one has done a murder fund to see how many hours a diode on a TEC cooled at 15C can do.
I think if we can keep the emitter temp below 25C the power we can get will be around 1W.
And based off what i have read and seen the new 500mw diode is not anything different besides again maybe a single pair of bond wires and a open can package to allow for better cooling.
But i now decan all my high powered diodes to make them last longer and to get a fraction less loss.
It may be these diodes are near identical and the differences comes from the package they are mounted to.
True open can diodes vs closed cans that are opened there is more thermal mass in the open can style.
Also it will be interesting to see andys results of the true diodes from mitsu vs the ones from our current suppliers.
The only difference might jut be a laser engraved symbol on the back but maybe there is more.
Also what is this about the 5deg thing? that is the difference between the expansion correct?

[planters]

What is Andy looking into?

I can't imagine that opening the can will lead to improved cooling vs. the overwhelming effect of the emitter's contact with the copper. I also would fear that the manufacturer placed them in a can to protect them. A single small speck of dust landing on the facet that is doing 2 MW/cm2 has got to shorten it's life. But, then why no can on the 73's? Doesn't make sense.

I agree that these are being under driven. I have too many projects going to tackle this, but a longevity test at say 80% of the dimming current with the diode mounted to a large radiatively cooled heat sink might be a good start. I would be happy to contribute.

[kiyoukan]

well it does not help as much as some think but it makes the diode emitter less of a hot box and allows more cool air from the heatsink to get closer to the emitter.
Yes this increases the risk of dust but anyone working on these diodes should be working with at least some sort of dust system.
Im my work room i got 2 dust filters one is a box fan with a hepa rated furnace filter and then the other is a ionic breeze.
So it helps push a few more percent of power (less heat) there was a test some time ago vs a 445nm diode with can against the same diode with the can removed. the improvement was under a 7% improvement but i cant seem to find that thread.
Another way i found to improve the power was build a tiny heatsink that went over the can and makes contact with the heatsink, this helped pull more heat away from the emitter. besides just using the case like we do now.
An example of how i made a cheap way to improve thermal contact on my 9mm diodes
http://laserpointerforums.com/f42/im...ml#post1059381
To try to make contact on as many sides and parts of the diode as possible.

[DTR]

I remember DTR running the 71 up to 1.7A. Do we know this is excessive or that it is less excessive if the 73's are run at this current?

It was 1.5A for 10 minutes. It did take it but I have not felt the need to drive one that hard again. I suggest 750mA. Over that based on the wavelength testing it seems to become less stable and I have noted in my testing when you get closer to 1A you get diminishing returns on output power vs the current increase.

[steve-o]

I'm thinking that with the appearance of the P73 500mW now available, with almost identical beam specs/ emitter size etc to the G71, this may change everything..
For me personally, I would like to use less optics, mounts etc.. , have less alignment hassles too. The diode price is double but 1/2 the optics and hardware may equal it out. Who is going to use the G71 vs the P73? Thoughts?