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Guidance on determining if I have a bad driver or diode, please...

-MTWallet-

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I have a 50mw aixiz laser unit that is a couple of years old that only had a dozen or so hours on it that has stopped working after being stored for a few months. I don't know if it is the driver or the laser diode that has died. I hooked a dummy load up to the driver and the DMM readings per what I have seen on the web (through three diodes on the load) seems to be in-line with the rated output. However the voltage measured at the LD+ and LD- points is only about 1.75v. I tested the laser diode using the diode test of the DMM and it reads 1.7v one way and 0v the other. All this leads me to think the driver is bad. One of the caps on the driver board is slightly bulged, so I pulled it and tested it but it reads alright at 1130uF for a 1000uF marked cap. I have a 2.5w blue laser that I could use to test the green one if that would be a sensible thing to do. And I have an old LM317 DDL driver circuit that I could use for testing also, but not sure what voltage to feed it for a green 50mw output.

Bottom line: Is this thing worth messing with, or do I just go on amazon and order a new one for $20? Photos attached of driver and laser head. Any guidance greatly appreciated!

20181219_221311 (Medium).jpg20181219_221348 (Medium).jpg20181219_221422 (Medium).jpg
 



paul1598419

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When you say this is green, what is the wavelength? If it is a 532nm green laser, then a Vf of 1.7 volts would be normal as it uses a 808nm pump diode. The board you call a driver is a SMPS circuit and likely includes a driver. But, if you can replace this whole unit for $20, that is cheap enough to make troubleshooting this one not worth the effort.
 

-MTWallet-

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When you say this is green, what is the wavelength? If it is a 532nm green laser, then a Vf of 1.7 volts would be normal as it uses a 808nm pump diode. The board you call a driver is a SMPS circuit and likely includes a driver. But, if you can replace this whole unit for $20, that is cheap enough to make troubleshooting this one not worth the effort.
Yes, 532nm is correct, sorry, should have specifically stated that. Thank you for verifying the Vf value. I was thinking that was the correct value, and the actual laser head is probably OK.

As to a new unit for $20. That was just kind-of an attempt at humor. I could get a 30mW diode/driver combo, but no heat sink or TTL. And sorry again, I forgot to say that the "driver" accepted 120v line power and then output to the laser.

Any thoughts on using the DLL circuit I have on hand to test with? Or the driver for the 450nm 2.5W that I have?
 

paul1598419

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There are 532nm lab laser for sale on eBay for ~$20.0 at 50 mW, so it is not out of the ordinary to find one like that. Because the 808nm pump diodes are case positive and because of the difference in power levels, you likely won't be able to use this driver for a 2.5 watt 450nm laser diode. You can pick up a lab laser above 100 mW for ~$35.00. I have one that does 230 mW and is actively cooled on eBay for $50.00.
 

-MTWallet-

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Thanks much for the input! I'll have a go at something off ebay and save this one for messing with later.
 

m3vuv

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I will just add my piece, you say you tested the capacitor,if its bulged its gonna be u/s,most caps will still measure the correct capacitance,its the equivelent series resistance thats important,normaly measured at 100khz,buy yourself an esr meter,one that tests under 500mv is best as can test in citcuit then in most cases.
 




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