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How do I fix a dell 50" plasma tv with no picture or sound? Answered

I have power to the power board but no power to half the board from the transformers over.

4 Replies

roger73142 (author)2010-02-04

Where can I buy the parts to replace detective item(s) on the power supply board. (U501) etc.

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mr12volt (author)2010-01-20

 Have a look at my instructable.

Your symptoms are not the same but the instructable describes procedures for debugging the power supply.  Without more information its hard to tell you how to fix it.  Start by probing all 10 of the power supply output voltages to see what they are.  This will point you in the direction of a sub circuit on the power supply that is not functioning correctly.  If the problem is not as simple as replacing one of the two AC input fuses, you'll need quite a bit of in depth circuit knowledge and equipment to implement a repair.  

If you find one of the power supply voltages not within spec, you'll have to trace back from that output, draw the schematic of that sub-circuit by looking at the components and their connections, figure out the circuit topology, guess which components are broken, probe them with a multimeter and/or oscilloscope, possibly unsolder them to probe the suspect component further, then replace with a similar component.  Be sure you plug the TV or power supply into an isolation transformer if you do any probing with your fingers or non-battery powered instrument.  

Good Luck.

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MahavishnuMan (author)2009-12-06

Another tip is, should you ever find this set beyond repair, don't buy dell monitors or televisions.

They are notorious for having issues, even in the laptop displays.  99% of the malfunctions seem to be a bad inverter for the cold-cathode tube in the back-lighting (a problem limited to LCD's, of course), but it seems there are many others who have even worse issues.

I think it really just stems from their apparent use of cheaply-manufactured components, but that's speculation on my part.

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Re-design (author)2009-12-05

If you've got power on one side of the transformer and not on the other then the transformer is probably blown.  And you need a new one.  If that's not what you meant then read on.

If you can't find a fuse blown, a wire or ribbon cable disconnected or another obvious malfunction you're gonna have to get it serviced if you don't want to buy another set.

There may be a fuse soldered to the board somewhere or the fuse may not even look like a fuse.

Also look for any obvious signs of parts blown, Burned resistors, bulged capacitors etc. and replace any that you might find.  If they're burned or blown replacing them may not buy you much time unless you figure out why they went poof.

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