Troubleshooting backlight inverter short to ground

[DLinkOZ]

Is there a good resource posted on this forum for this? I have an RCA L42FHD37 with a bad backlight inverter (6632L-0481A), and wanted to see if it was worth it/possible to hunt down the component failure. In the second picture, the two groupings of test points are shorted - the bottom 2 are positive and lead to the smd fuse below, the upper two are ground.

What I can find is in the group of 4 transistors just under the caps, two appear to be shorted. However, I realize it could be reading back from some other point in the circuit.

Case this be tested in-circuit?

[bammbammfran]

Re: Troubleshooting backlight inverter short to ground

The transistors do not appear to have cooked, But , One still could have gone out
There is a chance that one of the two ceramic capacitors between the one electrolytic capacitor and the one resistor went out, Those might be the easier ones to check first
But, With a dead short like this, you will more than likely have to remove parts.

Not sure what type of tester you have, but if it is a manual select, try dialing it up till you actually see resistance between the pos and neg on the board, even if it is miniscule. then recheck ground to ground and see if pos to ground is a little different, If it is a little different, then you may be able to locate the issue using this resitance reference

[DLinkOZ]

Re: Troubleshooting backlight inverter short to ground

Thanks, I'll check it out.

[DLinkOZ]

Re: Troubleshooting backlight inverter short to ground

I ended up doing a quick and dirty little test - I lifted one of the legs on two suspect transistors, and the short went away. So I suppose I can swap those out and move on.

[tom66]

Re: Troubleshooting backlight inverter short to ground

Not always - sometimes the driver IC will be damaged so you should consider replacing that too.