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FAP only drawing .4A??

Fauxtawn

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Jan 25, 2022
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I bought 3 FAP-79-30c-800-B bars.
l3jly-03_600.jpg
l3jly-01_600.jpg

One by one, I hooked them up to my Elenco power supply. I set the Voltage to 2V, but as I crank up the current it tops off at .4A. I am viewing everything through my Sionyx nightvision (for protection and to see the IR), and I see output, but not enough to smoke black construction paper I have the fiber pointed at.

512Vx6jsIGL._AC_.jpg


Thoughts on what's happening? When FAPs go bad, do they still put out low amounts of light? Not sure if it's my power supply or the bars.
One
 



CurtisOliver

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The problem I’ve found with cheap power supplies like that is you can’t get the current needed at such a low voltage. You need a power supply that is capable of high current at 2V. Otherwise you will struggle to get past the threshold on those diodes.

Edit: is the power supply pictured the one you are using? It’s only rated for 3A max anyway. You need low voltage high current for these diodes.
 

Giannis_TDM

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I bought 3 FAP-79-30c-800-B bars.
l3jly-03_600.jpg
l3jly-01_600.jpg

One by one, I hooked them up to my Elenco power supply. I set the Voltage to 2V, but as I crank up the current it tops off at .4A. I am viewing everything through my Sionyx nightvision (for protection and to see the IR), and I see output, but not enough to smoke black construction paper I have the fiber pointed at.

512Vx6jsIGL._AC_.jpg


Thoughts on what's happening? When FAPs go bad, do they still put out low amounts of light? Not sure if it's my power supply or the bars.
One
The vf changes with current, raise the voltage by a few 100s of mVs or so and they will start drawing more
 

Fauxtawn

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The problem I’ve found with cheap power supplies like that is you can’t get the current needed at such a low voltage. You need a power supply that is capable of high current at 2V. Otherwise you will struggle to get past the threshold on those diodes.

Edit: is the power supply pictured the one you are using? It’s only rated for 3A max anyway. You need low voltage high current for these diodes.
Yep, it's the one I'm using. I figured I'd do 3A just to test the bars, but I'll try with some buck power supplies I got laying around, thanks!
 

CurtisOliver

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I went up to 2.2V but was afraid to go higher. Still didn't draw more than .5A
Do not go higher than 2.2V. You just need a power supply capable of delivering the amps at low voltage. Problem is these supplies are expensive hence why I’ve only ran my FAP-I at threshold.
 

Giannis_TDM

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I went up to 2.2V but was afraid to go higher. Still didn't draw more than .5A
That is due to the ESR of your wiring setup/supply dropping the voltage or the supply being inaccurate at low voltages. Get a Korad power supply, not just for testing the FAPs but as a good and cheap well-made unit.
 




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