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paulz
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# Posted: 23 Jun 2016 11:01pm
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Dang, I was in a rush to get the 12vdc TV going for my wife before I went to work and jumpered it backwards. Took the back off hoping to see a fuse, no such luck. Did I kill it for good?
Newish LCD flat screen.
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darz5150
Member
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# Posted: 23 Jun 2016 11:36pm - Edited by: darz5150
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Did you have a cigarette lighter type plug in on the TV ? Did you reverse the polarity on the receptacle? Sometimes inside the plug in on the TV there might be be a fuse. If it has the cigarette lighter type plug.
I have 3 different DC TV's hooked up, as well as 12 volt lighting and 3 different 12 volt pumps.I use something similar to this, and a common negative ground buss bar connection. Also I put labels on the positive output wires. It helps to sort out problems if something pops a fuse.
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paulz
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# Posted: 24 Jun 2016 10:03am
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No such luck. The TV came with a 110ac wall transformer, I snipped that off and alligator clipped it direct to a battery. I had been using that way for months, and as I said, in hurry put it backwards.
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SE Ohio
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# Posted: 24 Jun 2016 02:45pm
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Might have blown an electrolytic capacitor? Cheap and easy to replace, they often go off like a shot (did you hear anything? smell anything?) and show damage, e.g. top blown open, scorch mark. They don't like reverse voltage. Might be able to spot the culprit.
A cheap properly sized diode can prevent current flow in wrong direction- I can send you one (free) if you get the set working. Will prevent problem on your next TV 
Good luck!
SE Ohio
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paulz
Member
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# Posted: 24 Jun 2016 03:01pm
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Thanks SE, I took the back off (hoping for a big old fuse, lol), here is a photo. I didn't hear or see anything, just the little red LED on the front no longer came on, nor anything else.
Yes, a diode, that would be a good thing.
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SE Ohio
Member
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# Posted: 24 Jun 2016 05:03pm - Edited by: SE Ohio
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Look carefully at the circuit board, as there could be a fuse soldered to the board and labeled "fu1", "f1" or the like. You'll likely have to scrape some coating of the component soldered ends to see if it has zero resistance like a good fuse. I sometimes use straight pins with clip leads for this multimeter test.
If you look at the circuit board like a clock face, is that capacitor (can) at 12 o'clock spreading open at the top? Cannot tell on my screen.
If a cap is replaced, make sure to use same or higher voltage rating.
Problem is most likely on board. Sometimes you can find replacement boards online? Cannot tell how difficult it would be to dig out/disconnect.
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paulz
Member
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# Posted: 24 Jun 2016 09:40pm - Edited by: paulz
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Wow, there it is, big as day. I put my VOM on the bare wire ends, open. Can I solder some leads and a replaceable car type fuse holder in there?
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SE Ohio
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# Posted: 25 Jun 2016 12:12pm
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Paulz, you can "sister" in an auto-type fused older, should work fine. That would be more elegant than simply soldering on a hair-fine wire strand...
Good luck!
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paulz
Member
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# Posted: 25 Jun 2016 12:26pm
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Thanks SE. Can't work on it till next week but I'll report back.
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paulz
Member
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# Posted: 28 Jun 2016 12:51pm
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It works! Thanks so much! So the TV draws about 30 watts, should I use a 3 amp fuse? And can I just go to Radio Shack down the street and get a diode to put inline to prevent future mishaps?
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SE Ohio
Member
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# Posted: 28 Jun 2016 05:02pm
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Great news on the fix! Nice to be able to repair things.
I'm assuming 12 volt operation.
Your local Radio Shack has diodes rated for 3 amps and a few hundred volts. A 4 amp or higher rating would be better, and they are cheap enough you can put two in series for extra safety. Voltage rating can be 12+ Volts.
The 3 amp fuse would need to be a "slow-blow" so startup surge won't knock it out quickly. Could also go with a 4-5 amp fast blow fuse.
Later,
SE Ohio
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