Electronics > Repair

led deterioration

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I have a solartron 7075 dvm, It displays ok but wont display an actual value of anything measured, As far as i can see the signal path goes thru an attenuator/signal conditioning then drives an optical chopper, The chopper has 4 led's and 4 photo diodes,my uestion is do led's get dimmer as they age?.
I suspect the chopper cct is iffy,does that sound a possibility?.

Kim Christensen:
Yes, LEDs do get dimmer over time. It's called lumen depreciation.

its why I push for use of digital isolators over optical isolators

I would rule out more likely causes before pulling apart an optical chopper assembly. Follow the service manual faultfinding procedures very carefully. Neon choppers are more likely to cause issues than LED ones.

Edit: Choppers fading are also far more likely to cause noisy readings than no reading at all.


--- Quote from: Kim Christensen on April 13, 2024, 02:40:34 am ---Yes, LEDs do get dimmer over time. It's called lumen depreciation.

--- End quote ---
Yep. Experienced such with old 5 mm standard LEDs. Green and yellow
being switched alternately for 10 s on and 10 s off over 30+ years.


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