Re: Gateway FPD1976w / LE1936 Inverter Madness



In my own stupidity -by not taking the time to label with CCFL leads I reversed them after flipping the power board over on the bench. Now with the 4 connectors seated properly, I am getting correct waveforms on all 4 inverter primaries and no more hot transformer or lamps. Still would not stay on.

Traced the problem to a noisy line on the v-sense to the pwm. Tracing the circuit shows an RC filter on that line. In an effort to calm down the line, I added an extra RC filter, similar to the smd components...

Re: Dell 22" monitor backlight goes out right away.




See here:
[URL="http://en.community.dell.com/support-forums/peripherals/f/3529/t/19285583.aspx?PageIndex=5"]http://en.community.dell.com/support-forums/peripherals/f/3529/t/19285583.aspx?PageIndex=5[/URL]

I fixed this monitor with the mod mentioned at the bottom:

[Then added a 2nd 1meg resistor in parallel with the 1st effectively making it a 500k resistor. Seems to be working great. Have had it running for several hours now....let's see how long this...

Re: Gateway FPD1976w / LE1936 Inverter Madness



I swapped both sets of leads and the transformer still was hot. All joints were soldered on caps, transformer and everything else that didn't look right. Solder generally looked good all over.

Here come the pictures...

It sure looks to me like the drive on the hot transformer has way too much spikes. What could cause this?

I'll wait for some comments before I translate the location of the transformers first. Then translate the location of the mosfets to see if I can isolate...

Re: Gateway FPD1976w / LE1936 Inverter Madness



I swapped the position of the lamp leads and the problem remains exactly the same. Guess the bulbs are ok.

Ohm'ed the transformer primary and secondaries. 2.8 ohms on both legs to common on both transformer primaries. 618 ohms on both secondaries. Cannot detect any problem on transformer with resistance measurements.

Pictures coming soon....

Re: Gateway FPD1976w / LE1936 Inverter Madness



I just noticed that the lamp that the hot transformer is running is also way too hot at the ends....

Hi,

I'm new here. Working on my first LCD repair!!

OK, it is opened up on the bench. Power on the display, the lamps in the panel power up for about 1 sec. then turn off, then turn on for about 1 sec. then remain off. The blue led power button remains on. (display from PC is working correctly and is visible with flashlight when inverter is down)

All caps look fine on the outside. Scoped the DC and everything is smooth.

I tacked a 1 meg resistor from vsense on pwm to ground to keep the inverter running. 1 of the 2 inverter transformers...