Why did my 642nm diode die?

[DTR]

Where are people "harvesting" these 642nm diodes from?

The ones I have are from Avnet



It seems they are out of the 150mW 642nm the OP said he had but to call for availability. But they have a 637nm in a 170mW and a multimode 637nm 250mW.
http://avnetexpress.avnet.com/store/...lers=&x=24&y=3
Datasheet
http://www.opnext.com/products/pdf/o...1_hl6385dg.pdf


170mW 637nm

http://avnetexpress.avnet.com/store/...ction=products
Data Sheet
http://www.opnext.com/products/pdf/o...133dg_Rev1.pdf





250mW multimode 637nm

http://avnetexpress.avnet.com/store/...1&listIndex=-1
Data sheet
http://www.opnext.com/products/pdf/o..._hl6388mg2.pdf

[catalanjo]

The ones I have are from Avnet
It seems they are out of the 150mW 642nm the OP said he had but to call for availability. But they have a 637nm in a 170mW and a multimode 637nm 250mW.
http://avnetexpress.avnet.com/store/...lers=&x=24&y=3
Datasheet
http://www.opnext.com/products/pdf/o...1_hl6385dg.pdf
170mW 637nm
http://avnetexpress.avnet.com/store/...ction=products
Data Sheet
http://www.opnext.com/products/pdf/o...133dg_Rev1.pdf
250mW multimode 637nm
http://avnetexpress.avnet.com/store/...1&listIndex=-1
Data sheet
http://www.opnext.com/products/pdf/o..._hl6388mg2.pdf

Hey, thanks for the info DTR ! .... but are these "harvested" or new from manu ?

This hl6388mg2 diode is new to me. 250mw @ 637nm sounds really good, although I see that the can is not isolated.

Has anyone tried to tame the output of this beast ?

Cheers

[kitatit]

Why don't you just snip them shorter with wire cutters so they match the harvested length?

Seems to me would remove the problem.

It wasn't really a problem. Was just speculating that it could have been a long shot cause of this inexplicable death.

Where are people "harvesting" these 642nm diodes from?

Sorry I was referring to cheap 445 diodes.

Did you drill Dave's back plate out to 5.1mm so that the bug socket could enter right up to the diode ??

No, I didn't want to reduce the heat dissipation surface area any further.

The opnext spec sheet doesn't show the leads as being very long.

Ha! you are right, after measuring several different diodes they are no longer than anything else. Well they are long enough to be exposed when untrimmed and using a Laserbug. I'm mostly using Laserbugs while I'm testing so I can swap diodes around without having to keep re-soldering each time. I'll be hard wiring them when they go in my projector

The only tricky bit I can see is placing the (drilled out) back cover over the diode pins where heat shrink might well come in very handy. How did you deal with that bit of the mounting procedure?

Also what collimating optics are you using?
Are you knife edging?
Any ideas about telescope optics?

Cheers

With an anti-static mat and wrist strap connected I put Dave's mount face down applied Arctic Silver thermal compound to the mount and fitted the diode. Then I used some insulation I stripped off some wire as I didn't have any heat shrink small enough to insulate the diode pins. Next I applied a small amount of compound to the back cover, position the back cover, fitted the cap screws and connected the Laserbug.

I'm using McCarrot lenses one for blue and one for red. I'm happy with them.
The beam specs from my 50mw 445nm blue is a perfect match for the 642.

"Are you knife edging?" No this configuration is for my mini projector which needs to be quiet compact. It will only have one red, one blue and a green. It will be the same foot print as a 15" notebook and 50mm thick.
This projector doesn't need power, just decent beam specs, compact and reliable.

It is for learning about projector building and for learning how to use the software so I'm
prepared when my large projector build is ready for prime time.

"Any ideas about telescope optics?" No I'm still a grasshopper, I'll save telescope optics for when my knowledge is more advanced

[dnar]

No, I didn't want to reduce the heat dissipation surface area any further.

Kit, the rear plate is not the only heat dissipation area, the seat the diode sits in is!

Also, I would be reluctant to drill this out, I found with virgin 826 diodes that 2 of the 6 mounts I have the diode was not adequately secured with the plate screwed tight, and the diodes could still be rotated! This was cured with a little tweak of the rear plate under force.

Do you feel like your being questioned by the Coherent Gestapo in this thread?

[kitatit]

Kit, the rear plate is not the only heat dissipation area, the seat the diode sits in is!
Also, I would be reluctant to drill this out, I found with virgin 826 diodes that 2 of the 6 mounts I have the diode was not adequately secured with the plate screwed tight, and the diodes could still be rotated! This was cured with a little tweak of the rear plate under force.

Yeah the back plate would be a secondary dissipation path but I'd like to maximise its potential. With a press fit housing I roughly calculated there is 24mm\2 direct surface contact between the diodes heat sink and the mount. With Dave's It is about 9mm\2 on the front and 9mm\2 on the back. The 24mm\2 of radial surface area is coupled to the mount via a 0.05mm (2 thou) air gap filled with Arctic Silver.

Do you feel like your being questioned by the Coherent Gestapo in this thread?

Maybe... but a punk kid's got to learn some how

[steve-o]

A 1 watt zener diode seems to protect the LD well, I've found. Across the leads and barely conducting, it will gulp up a voltage spike no problem.

[DTR]

Hey, thanks for the info DTR ! .... but are these "harvested" or new from manu ?

This hl6388mg2 diode is new to me. 250mw @ 637nm sounds really good, although I see that the can is not isolated.

Has anyone tried to tame the output of this beast ?

Cheers

From what I understand they are new from the manufacturer.

I have mine underpowered quite a bit @ around 300mA with the Max being around 430mA. I am getting 125mW out of it.



Here is the dot with an Aixiz red ar coated glass lens. It has a small line in it which I have also seen on a LOC.




Here is the raw output. Pretty close to the look of a 445.



Here is how the diodes comes. Did not get a picture of the pins but they are long and clean.

[catalanjo]

From what I understand they are new from the manufacturer.
Here is the dot with an Aixiz red ar coated glass lens. It has a small line in it which I have also seen on a LOC.

Thanks man !
How big and how far from the aperture was this dot. (difficult to tell from the pic!).

Cheers

[DTR]

Thanks man !
How big and how far from the aperture was this dot. (difficult to tell from the pic!).

Cheers

Sorry I did not list it as I don't have a ruler or anything in the picture to give it some scale. It is right about 5 feet.

[catalanjo]

@stev-o
What voltage zener are you using ?

@kitatit,
Many thanks from the "Coherent Gestapo" ...... very useful info.

Cheers