12v L.E.D Light Bar

[thorthor]

I have a 12v L.E.D light bar it has 60 leds(20 in series and 3 of those in parallel if im not mixing that up). The center 20 leds just barely light up, so I poked around with my multimeter like one does, every led works when tested, but when I measured everything while 12v was applied the driver circuitry for the center measured 55-60v but the other 2 drivers only went to 12v. I compared sections and everything measure the same till I get to 2 caps where I get the 55-60v, am I wrong in thinking its a bad inductor. ....... Its an old light bar that was on a truck it did have water work its way in.  I did clean everything up with a nylon brush and alcohol, to my eye no leads or pads broke/rusted off.  Thanks for any help/advice etc.

[Jwillis]

  Could be anything  . A bad driver chip , transistor , shorted cap even a burned resistor can exhibit higher resistance than it should . 60V for 20 white LEDs in series seems about right .  2.7 to 4  forward volts is typical of white LEDs . If you could check the Forward voltage of one of them with diode setting on your DMM and multiply that with 20 that will give you the total forward voltage of the string.
Could you take some clear pictures of the driver board ?

[thorthor]

You're absolutely right, forward voltage hadn't even crossed my mind. And yea I can take one quick. Sorry for the late reply btw. is this one good? Its from 1 of the working ones there's 3 driver circuits on the board in total all 3 are copies of each other, the one shown is the one I could get the best picture of due to how my work space is set up. I no some of the silkscreen is flecking up in places but I think there's another layer beneath cause its not conductive at all.