Insignia NS-LCD37 : No Backlights

[culcuhain]

Ok. I am stumped on this one.
Tv has Standby and turns on. No back lights. Not even the 2s to black.
I have the normal voltages on the Power Board that I should have when in Standby and powered on.
I have the same issues on 2 inverter boards.
On the inverter board I have 23.7VDC across all three fuses (2 ceramic and one tiny green on)
Transformers S1-S2 and S3-S4 all read between 2.20 and 2.31 k Ohms (both boards)

On the Connector in the picture here are my voltages and why I am stumped.
(not listing the voltages for the grounds.)
Pin # Label Stdby On
1 VBL 0.035 23.70
2 VBL 0.035 23.70
3 VBL 0.035 23.70
4 VBL 0.035 23.70
5 VBL 0.035 23.70
11 VDIM 0.008 1.60
12 BLON 0.001 0.27
13 E_PWM 0.715 3.30
14 PWM 1.3MV 2.40

To me it looks like the BLON (turn on signal is there but too low)
thoughts?

[budm]

Re: Insignia NS-LCD37 : No Backlights

"12 blon 0.001 0.27"
<1V = off

[culcuhain]

Re: Insignia NS-LCD37 : No Backlights

Bad main board then eh?

[R_J]

Re: Insignia NS-LCD37 : No Backlights

If the E in "E_PWM" stands for Enable and not Error, I would trace the Blon wire back to the main board and see if its not a bad switching transistor, You could remove the blon wire from the inverter plug (to isolate it from the main) and apply around 3 volts to the blon at the inverter and see if it turns on.
If the E stands for Error the inverter could be telling the main board not to turn on the inverter

[culcuhain]

Re: Insignia NS-LCD37 : No Backlights

Ok. Used main board shows up. Hook everything up. I have backlights and picture... no sound. Grrr. Might have gotten a bad main board. Time to track that down. :S

[culcuhain]

Re: Insignia NS-LCD37 : No Backlights

Definitely replacement board is bad. I hooked up the old board and disconnected the BL-ON signal cable from the main board to the power board. Back lights come on. Hook up an input and BAM. I got audio with picture. Board goes back tomorrow.

[culcuhain]

Re: Insignia NS-LCD37 : No Backlights

Received RMA'd board back. TV is good to go. Old main board just has an issue with the backlights not sending the signal to turn on.

Just curious. I know if I disconnected the BL-ON cable from the main to the SMPS that the backlights come on. Any harm in leaving that disconnected for long term use or would feeding it the correct voltage from a different source work as well?

[budm]

Re: Insignia NS-LCD37 : No Backlights

The BL-ON is applied to the backlights circuit AFTER the PS-ON is present to turn on the rest of the power supply so the power supply will be stable first before the backlights circuit (which draws lots of current) is activated, this help reduce the inrush current.
You may be able to used the switched 12VDC that feed the T-CON board for controlling BL-ON through 2200~2400 Ohms resistor.