O.T. Fixing a power inverter


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Posted by D Sherman on Saturday, November 22, 2008 at 13:48:36 :

In Reply to: server or something is down posted by chuck on Saturday, November 22, 2008 at 08:09:26 :

Thought I'd pass along a successful fix for an inverter I used to run my power tools out in the boonies. It's a "Chicago Electric" (Harbor Freight) "2000 watt / 4000 watt peak" inverter. That's a lot of watts for $150, which is why I bought it. I like it a lot better than a generator because it's silent and easy to start and stop as often as necessary. I run it off a dedicated car battery, which I charge up now and then.

The problem was that it very often wouldn't start up in the morning when it was cool or damp. Just a normal morning out in the woods and it wouldn't work. I exchanged one, but the replacement had the same problem. The only clue it gives you about what's wrong an indicator light that comes on green if it's working and red if it's not. I finally got to thinking that maybe it was condensation on the circuit board that was keeping it from working, so I tried drying it out, either on the wood stove or under the heater of my truck. Either one would fix it so it would start that day.

I took it back to town, took it all apart, and found the reason for the problems. The soldering flux was never washed off the board! I knew that due to environmental rules, they've been going to "no clean" soldering processes, but I never thought they'd leave gobs of hygroscopic flux all over the boards. I tried to scrub it off with water and then with alcohol, but it took brushing with lacquer thinner to get it all off. I blew it dry with air and let it get good and dry in a warm place. Then I sprayed both boards on both sides with two coats of silicone conformal coating (M G Chemicals #422A-340g). That was back in September, and I used it all during the fall when the weather was getting progressively colder and wetter, and have never had a problem with it since.

If you have any problem with electronic devices not working in cold or damp weather, it's worth taking them apart, cleaning the boards thoroughly, and spraying them with conformal coating. The stuff is kind of expensive ($18/can) but it was well worth it. It will also keep the boards from corroding due to ongoing dampness. Most PCBs in military equipment are conformal coated for this same reason.



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