P73 doesn't do what it should do

[neutrino]

Oh, I think I was running my flexmods on 5 volts too for the P73. I will have to double check when I get a minute.

[jeejeedr]

I had some time to investigate a bit further.
When removing the cylindrical optics to measure, but before removing the 2mm collimator I noticed that the projected line was interupted.
When ramping up power I noticed that the different parts (probably different emittors) do not increase in power in the same way.
I even saw some points decreasing in intensity when giving the diode more current.

The photo is assembled from 6 different photos, taken from the same position with the same aperture, shutter speed and iso each time.



I think this indicates that part of the emittors are not working. (and hence the lack of power)

[steve-o]

Possible COD ..

[jeejeedr]

I think it was a bad diode from the start going on the fact that it didn't deliver the power from the start.

[m0f]

I had a similar problem with 1 p73 out of 10 that I purchased. As the smallest speck of dust can cause be enough to cause problems being an open can diode, I think some doa's are to be expected to some degree.

[The_Doctor]

I had a similar problem with 1 p73 out of 10 that I purchased. As the smallest speck of dust can cause be enough to cause problems being an open can diode, I think some doa's are to be expected to some degree.

Yes. Given how tiny the emitter area is, this is extremely likely. It's one of the reasons I went with G71's recently. Washing with very pure acetone is a possible help but even that hassle is uncertain unless the entire lens, barrel, mount are all equally cleaned and assembled in conditions that are usually owned only by semiconductor factories. Most collimating lenses are designed for use with 0.3mm glass windows on diode cans too, and with very short focal lengths, may work badly without the window.

I know a lot of people use uncapped diodes, but in this case the risk of poor performance, or no performance, was too much for me. The lens barrels I have contain a powdery substance lining the inner bore, probably dried residue of cutting fluid/lubricant used in lathing. I found I could remove it easily by threading a shoelace through the centre and running the metal part swiftly along the stretched lace a few times, then making sure that fibres from the lace weren't left behind in there. Anything like that might easily find its way onto a diode facet sometime if not rigorously removed first.

[ZeroPoint]

I just got a P73 last night from DTR and had a chance to fire it up. I focused it as narrow as I could, set the thermopile approximately 1cm from the diode and fired it up to 400mA.... 180mW. I was scared for a second until i decided to double check what the operating current was. AHH! 500-800mA. Ok, so I cranked it up to 850mA and..... 360mW Started to get worried again. So I hopped on the forum and started looking through threads related to the P73 and came across this one. I saw Swamidog's post and realized that I'm powering my flexmod with a 5V supply as well. I pulled out an old Xbox power supply (12V supply) that I've modified a bit and hooked that up instead. This time it went to 385mW (Slight improvement but it may actually have been a result of a shift in the position of the laser in relation to the thermopile from the first test). Then i decided to adjust the module in the heatsink so that I could place the lens directly in front of the thermopile (about 1mm) and the measurement went up to 420mW. Finally I took the lens completely out and left the module approximately 1mm away from the thermopile and the measurement skyrocketed to 630mW. Now, I have a nice solid line with no interruptions or black spots so it's possible your issue is different but in my case the loss of power is simply caused by the lens (glass lens). So now my question is - is there a lens out there that would work better to minimize that loss? Maybe a G-2 lens, or is this loss inevitable because of the emitter design? It seems a shame to lose 200mW before the beam has even left the module.

[steve-o]

So now my question is - is there a lens out there that would work better to minimize that loss?

The 2mm aspheric sold by Dave. All my p73s operate @ 830 ma in/ 650 mw out w/ no tec just ambient cooling and heatsinks/fans with no problems. I limit the exposure to outside air to just a few seconds, being open can so that no dust will settle on the delicate innards

[ZeroPoint]

Thanks Steve-o, I will invest in an aspheric lens from Dave.

[steve-o]

Thanks Steve-o, I will invest in an aspheric lens from Dave.

You're welcome ZeroPoint. I would also get the lens holder from him too because the lens is very small and is difficult to mount otherwise.