The parts required are 3mm 850nm for DS-2CD2142FWD-I. About a 2 hour job per unit.
Tools -
Solder sucker like this.....YIHUA 929D-V Electric Desoldering Soldering Iron Solder Sucker Desoldering Pump , Amazon
Copper De-solder wick
Flush cut nippers to straighten bent leads after desolder and to trim leads of LEDs after install
Soldering station with adjustable temp and small half chisel face tip
YOCTOSUN LED Head Magnifier, Rechargeable Hands Free Headband Magnifying Glass with 2 Led, Professional Jeweler's Loupe Light Bracket and Headband .....Amazon (not required but sure is helpful for older eyes)
I got my LEDs from Amazon, 100 to a pack, enough for three cameras.
CHANZON 100 pcs 3mm Infrared Ray IR 850nm Emitter LED Diode Lights (Clear Transparent Round Lens DC 1.4V-1.6V 20mA) Lighting Bulb Lamps Electronics Co
These were $10 a pack. If you wanted to wait awhile you can get these much cheaper from Alibaba or Bang Good.
The primary difference in the replacement units above and what was removed from the board was the placement of the flat spot indicating polarity. The removed units had the flat spot on the side of the negative, short leg of the LED (standard) while the replacements had the flat spot on the face of the LED with the negative, short leg to the right (nonstandard). The PCB has an orientation symbol silk screened on....to place the replacement in the right orientation turn the board so the image has the flat spot on the bottom as you look at it then place the replacement short lead to your right and insert. Easy peazy. In any event you should check the LEDs you use to make sure they didn't place the flat spot in some screwy orientation. Negative lead should always be shorter, tho.
