Re: cicero lcd inverter IC replacment needed

Success!
I obtained some samples of the Alpha & Omega AO4606, and replaced the one on my inverter board that was toasted (U105, I think, but I forgot to make a note of it; it was in the blackened PCB area). Connected the LCD panel back up, plugged in the AC, pressed POWER, and presto! the power LED went on and the LCD panel, after a few seconds, gave me a nice "NO SIGNAL" image. Connected it up to a PC video output, and the display works fine.

So, to summarize:
- replaced several bad/bulging...

Re: cicero lcd inverter IC replacment needed



Oops...one more thing. On my unit, that BL pin was at about 1.25V DC, and the backlight (when it came on for the 1 second) was quite visible, but not hugely bright. Maybe try the brightness adjustment buttons on the display, see if you can see that BL voltage change? Is it possible that the 0.25V you see means "set the backlight very dim"?...

Re: cicero lcd inverter IC replacment needed



That's what I also thought initially, but I traced that line over to the BIT3191 chip. I now believe that this is an analog voltage input (driven by the LCD display controller board) that determines the brightness of the LCD backlight. I don't have my hand-drawn schematics here at work, so I can't give you any details right now.

I'm also curious about the one other signal pin on that 10-pin connector (pin 9?)....

Re: cicero lcd inverter IC replacment needed

I also have one of these Cicero displays with exactly the same problem. I replaced all of the bulging caps with new ones. I also had to replace the 47uF/25V cap on the primary side of the switcher. Now, the +5V and the +12V come up fine.

There are two separate backlight inverter sections, both controlled by the BIT3191. One of the circuits is fine, and the other is blackened, just like the photo that was posted. At least one of the dual-MOSFETs in that circuit is toasted. I have manually traced out quite a bit of the...