Insignia NS-LCD47HD-09

[Butcherpet@yahoo.com]

Hello all, first post. Got this older TV for free has power but no backlights or picture. Tested voltages and it seems everything is there but the 3v BL ON. I know the inverters are a common failure with the fuses but they checked good on this one. So my guess would be the main board having a faulty component? Or does the BL ON come directly from the power board with the 24v to inverters?

[CapLeaker]

Re: Insignia NS-LCD47HD-09

BLon is generated from the main board's main IC. There are 2 ways of fixing this: either you need a new main board, or you can try to disconnect the BLon wire from the PSU and jump STBY through a 1k resistor to BLon pin on the PSU (or some other 3 to 5 v source).

[Dannyx]

Re: Insignia NS-LCD47HD-09

+1
Try jumping 3v to that pin somehow. A lab bench power supply or wall-wart adapter makes this easy, just make sure you connect the ground to the chassis. If the light doesn't come on, there's a fault with the inverter. If if does come on, the main board is not sending the BL-ON signal, so you either replace the board (which may or may not be worth it), or grab a 3v signal from somewhere else to "jump-start" the inverter every time you power on the TV....or indeed, attempt to troubleshoot the board if you manage to find the schematic to see where that signal is supposed to come from.
EDIT: remove the pin corresponding to BL-ON from the main board end so you only send your 3v into the power supply side and not the main board...depending on the connector, sharp enough tweezers can achieve this, since it usually involves slightly bending a piece of plastic holding the metal pin in the plastic connector shell along with the others.

[Butcherpet@yahoo.com]

Re: Insignia NS-LCD47HD-09

Ok tried to jump bl on with 3v did nothing. I also see no picture/menu on the screen with flashlight. Just strange to have all the correct voltages besides the bl on. I did notice I have a ribbon cable from the t-con board to the master inverter would that be something to do with the bl on feed thru the t-con? I tried removing the ribbon from inverter then jumping with 3v but still nothing.

[budm]

Re: Insignia NS-LCD47HD-09

So did you remove the BL-ON wire back to the main board FIRST before jumping the BL-ON pin with 3V?

[Butcherpet@yahoo.com]

Re: Insignia NS-LCD47HD-09

Pretty sure it is the mainboard I tried testing the very thin wires and connectors from the mainboard to t-con and got nothing so the mainboard is not sending anything to the t-con which is probably on the same circuit as the bl on volts.

[budm]

Re: Insignia NS-LCD47HD-09

The key point is that if the BL-ON is present then the backlights should be on.
The T-CON gets switched 12V from the main board, that 12V is from the power supply switched 12V.
We want to know if you have more than just main board or not by testing the power supply board by forcing on the Backlights, but you are not telling us if you did disconnect the BL-ON wire going back to the main board first or not, if you did not you could have damage the BL-ON drive circuit.