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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Sep 18, 2012 6:37 pm Post subject: |
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It is possible you have a bad lamp. I have had them where they would arc and sizzle near the connector or transformer and found the end of a lamp cracked and/or broken. Maybe time to check the lamps for visual problems.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Tue Sep 18, 2012 6:45 pm Post subject: |
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| macgyver655 wrote: | | It is possible you have a bad lamp. I have had them where they would arc and sizzle near the connector or transformer and found the end of a lamp cracked and/or broken. Maybe time to check the lamps for visual problems. |
The thing about that is I didn't even have the lamps plugged into the board. I only connected CN6, CN7, and of course the wall outlet connection.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Sep 18, 2012 6:50 pm Post subject: |
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| Jakeklem wrote: | | macgyver655 wrote: | | It is possible you have a bad lamp. I have had them where they would arc and sizzle near the connector or transformer and found the end of a lamp cracked and/or broken. Maybe time to check the lamps for visual problems. |
The thing about that is I didn't even have the lamps plugged into the board. I only connected CN6, CN7, and of course the wall outlet connection. |
Well there's your first problem. Lamps need to be connected. It's like not connecting the high voltage leed in a CRT and just letting it hand. That voltage wants to go somewhere.
If it still sizzles when connected try to see the exact location and post me a picture.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Tue Sep 18, 2012 7:10 pm Post subject: |
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hm interesting, I wasn't aware of that as i'm not familiar with CRT's. Anyways, I plugged it all in and I'm getting a back light flash for a split second upon pressing the power button. At least something is working! 
So correct me if I'm wrong, but it appears that my fears from the original post are confirmed! The lamps went bad. Any chance lamps from a vizio gv47l would fit?  I have one laying around with a cracked screen.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Tue Sep 18, 2012 7:18 pm Post subject: |
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I would open up that light box and make sure you have a bad lamp. Then you can see what you have in there.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Wed Sep 19, 2012 10:06 pm Post subject: |
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Ok I got into the light box and it's pretty obvious where the problem is. There is a nice burn under one of the bulbs. Any hints on removing the bulb without snapping off the little plastic clips?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Sep 20, 2012 12:53 am Post subject: |
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What's the length and diameter of the lamp?
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Thu Sep 20, 2012 2:39 am Post subject: |
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41" x 1/4"
Is it common for it to arc to the metal housing like that?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Sep 21, 2012 12:01 am Post subject: |
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It will usually arc to gnd when there is a bad lamp. I would also check that cap for short. You could also try swapping that lamp in another position and try to connect everything with the lamp box open and power it up and see if more then 1 lamp doesn't attempt to light before shutdown.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Sep 21, 2012 12:13 am Post subject: |
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Have you opened up that broken screen tv you have to see what lamps it has. New lamps are coming in at around 25 bucks a piece but I'm not seeing your diameter. Are you sure about the diameter?
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Fri Sep 21, 2012 6:17 am Post subject: |
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| macgyver655 wrote: | | It will usually arc to gnd when there is a bad lamp. I would also check that cap for short. You could also try swapping that lamp in another position and try to connect everything with the lamp box open and power it up and see if more then 1 lamp doesn't attempt to light before shutdown. |
To check the cap... Do I need to unsolder it from the board? I can just test it with the capacitor setting on my DMM right? Any suggestions on removing the lamp in one piece without damaging the little plastic clips holding them in?
| Quote: | | Have you opened up that broken screen tv you have to see what lamps it has. New lamps are coming in at around 25 bucks a piece but I'm not seeing your diameter. Are you sure about the diameter? |
I've yet to tear into the donor set, got a bit busy today. I should have time tomorrow. 25 is more reasonable than I expected. Hmmm, I used a tape measure to get an idea, i'll use a caliper tomorrow. Do they typically measure in inches, mm, or both?
hmmm I've wondered how hard it would be to do a led conversion for quite a few years now, before they started building them that way commercially. Maybe this can be my chance 
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Sep 21, 2012 4:13 pm Post subject: |
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I would just test that cap to make sure it's not shorted. diode scale should have no flow either direction. Leave it on the board.
Lamp measurements are in MM. The lamp diameters in that length are around 3.0 and 4.0 mm.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Fri Sep 21, 2012 5:07 pm Post subject: |
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Cap looks good, I get nothing both ways and the others test the same way.
Ok, I gave the measurements in inches. So 41 inches converts to 1041.4mm and 3.4mm is the diameter. I said 1/4 inch previously when it's actually 1/8 inch.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Fri Sep 21, 2012 6:15 pm Post subject: |
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The bulbs from the donor set are about 1/2 inch too long. darn.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Fri Sep 21, 2012 7:39 pm Post subject: |
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Did you try switching lamps around and power it up to see how many don't light? How many lamps does it have?
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Fri Sep 21, 2012 11:55 pm Post subject: |
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Ok I hooked it all back up and it looks like ALL of the lamps are trying to light up for a split second, even the one thought to be bad. However, I noticed a zap sound coming from the power supply when the lamps turn on. I dimmed the room lights and plugged the tv back in. Sure enough, I could see a spark around the area circled in red in the picture. This is the secondary side of the transformer correct?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Sep 22, 2012 12:23 am Post subject: |
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Is that the replacement transformer from the other supply?
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Sat Sep 22, 2012 1:13 am Post subject: |
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Yes it is. Perhaps I bridged it with solder?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Sep 22, 2012 3:02 pm Post subject: |
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At this point you have so many things wrong it's hard to determine where to go. You definitely had arcing in multiple places. The burn hole in that board may have an open connection somewhere. I would probably push it aside until I had another tv with the same boards and test your current boards in it, so see what is good and what is bad. It could still be a bad lamp but it's still trying to light. Or look for a similar tv with a broken screen and just put your screen in it. Those screens interchange with a lot of different brands. Check that other one you have with the broken screen. It may interchange.
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Jakeklem
Joined: 18 Aug 2010
Posts: 45
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| Posted: Sat Sep 22, 2012 5:20 pm Post subject: |
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It might be a long time til I get a similar set. I only do this on the side and don't get many sets to begin with. I used the power board out of the donor for a previous repair, so even if the screen would swap it wouldn't work. The only other set I have to work on right now is a 32" vizio that I believe has main board issues. I'll start another thread for that one.
I ended up plugging the set directly into the doner set light box and get the same result. Lights try to come on for a split second and there is a spark on the same transformer.
Also, I took pictures when I soldered the relay and transformer to the board. There is one solder point, only on the bottom of the board, that seems to come from nowhere.
In the pictures, Blue box is relay, Red is the random solder point, and Yellow is transformer.
In the first pic, the red box indicates where the random solder point would be if it were on both sides.
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