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Old 02-18-2013, 06:45 PM   #43
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I recently replaced all the florescent bulbs in our trailer with these LED strips from Amazon, and everything was great for a while.

Now the one in the bathroom, the 18 incher that I installed six rows in has gotten very dim. I've checked the voltage both at the switch and at the strips, and it is good.

What could have caused these LED's to go dim?
My guess would be a short or high resistance at one of your connections. Can you check the voltage on the solder connection points on all of the individual strips and see if there is a difference? You could also try to re solder the connections to the power, maybe a cold solder joint?
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Old 02-18-2013, 07:08 PM   #44
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My guess would be a short or high resistance at one of your connections. Can you check the voltage on the solder connection points on all of the individual strips and see if there is a difference? You could also try to re solder the connections to the power, maybe a cold solder joint?
I did check the voltage at the individual stips and it is fine, same as at the switch. I seriously doubt that all six of the joints would go bad after two months, all at the same time, and all at the same rate. I think the odds of that happening would be higher than winning the lottery.

All the rest of the lights in the trailer are fine.
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Old 02-19-2013, 09:12 AM   #45
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Ha! Bad ground (sticking my neck out here, having not been able to handle the patient...).

Here's why you could be getting good voltage readings--you're measuring from the switch (or LED strip) to a point on the shell (between points A and B). I bet your ground wire from the fixture is bad, or the place where the wire is attached to the shell is corroded. That means you've developed a resistance (C) in the ground lead. If you measure between A and C you'll see something like 8 volts.

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(there is no physical resistor, of course, it's just symbolic of something wrong in the ground wire.)

Zep
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Old 02-19-2013, 09:58 AM   #46
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Ha! Bad ground (sticking my neck out here, having not been able to handle the patient...).

Here's why you could be getting good voltage readings--you're measuring from the switch (or LED strip) to a point on the shell (between points A and B). I bet your ground wire from the fixture is bad, or the place where the wire is attached to the shell is corroded. That means you've developed a resistance (C) in the ground lead. If you measure between A and C you'll see something like 8 volts.

(there is no physical resistor, of course, it's just symbolic of something wrong in the ground wire.)

Zep
Actually, my first voltage measurement was from the switch output to the ground wire, and I got normal battery voltage (12.66 with no charge going to the battery).

My second voltage test was at the solder point on the strips where the wires are soldered on, again I got the same voltage as above.

My third voltage test was at one of the cut points on one of the strips where the foil is exposed for soldering, and again I got the same voltage.

Since I first posted about this problem I've been researching on the net, and found that LED's will do this if they've been overheated in operation. Since I installed six strips (three on each side where each florescent tube went), all very close to one another, I'm thinking this may be the problem,
so my next move will be to replace the strips with some spacing so they won't run so hot.
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Old 02-19-2013, 12:39 PM   #47
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Looks like to took the right voltage measurement.

On the other hand, I find it hard to believe that all the LEDs decayed in the same way over the same short period of time. This is very interesting.

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Old 05-14-2015, 11:55 AM   #48
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I see an LED liftime versus supply voltage test looming on the horizon. You would need a control LED that is only lit while comparing the long terms. I expect that 13.5-14V is too much for these things.

I had a brand new LED screw type AC powered LED bulb die in a month at home. I had high hopes for these and it is dead in a month. I may contact GE and see if they will replace it. LED still has its issues. The harder you drive these things the lower the liftime. A volt or two does matter. Also there are different grades of these things. Some will last longer than others.

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Old 05-14-2015, 01:36 PM   #49
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So far the strip LED's that I installed back in 2012 are still working fine. There have been several different batches for sure, and none have been expensive, around 10 dollars a roll. I played with some of those round LED's that Zep used and last I checked there was about one diode left burning out of all of them. Quality of some of these small 12v bulbs is sketchy, though I'm not so sure its the voltage that kills them but rather the heat and maybe just marginal quality components. I think what helps the strips is gluing them to metal backs which draws away excess heat. I havent checked voltages lately/ever, but initially there was a univolt and it was replaced with a PD unit that keeps power on 24/7.

I am branching out a bit with LED's I have the two bunk lights that were the last holdouts on incandescent and will be replacing them with these:



Time will tell how well they last. I've bought some little 110v GU10 mini floods for the house and those suckers last maybe a year or two before they burn out. These were the typical chinese 2-3 dollar bulbs. If I had paid 15-20 each like they charge at the big box stores, then I'd be mad. But at the cost, you pay for what you get.
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