Re: Six Acer V173 LCD monitor all with same problem, only display Win 98 640res

I have another faulty V173 showing Acer logo. Is like the MCU find every VGA signal as incomplete and went to a "parking" mode turning off backlights. I dissasembled the panel to see if there is an image without backlight but the LCD appears turned off completely.

I found a Service manual for a very similar monitor (same control board) and there is no hope: "No Image" troubleshooting end very fast with "change scaler and mcu" RTD2120L and RTD2025

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Re: HP Pavilion All in one power converter led backlight : how Mobo dim lights?

Well i made some experiments and clearly i misidentified that little chip: well under 10 volts control voltage created by that chip continues to be 1.2 v as required by MP3389 controller.
Maybe is a transistor or something but clearly is a signal conditioning for an external PWM not a PWM itself. I didn't try but an external PWM connected to pin 4 IK-CVB20 Pegatron will dim backlights for sure.

Re: HP Pavilion All in one power converter led backlight : how Mobo dim lights?

Thanks for reply:
It's a SOT-23 six pins version. It's possible to mix up both of these pins in that package but i see again and my measurements were correct. I will try to put less voltage (maybe 11 volts) to see if something changes.
I connected the panel backlight and is working at full power, it's too bright. I used a damaged LG 20M35a-b monitor main board to drive the panel but that monitor uses a backlight led strip with higher voltage 40volts vs 27 volts in the HP All in one Samsung...

Doing reverse engeneering to a IK-CVB20 Pegatron "inverter" board from an HP Pavilion 20f295la I found there is no real dim signal from Mobo.

Pin 1= GND
Pin 2= GND
Pin 3= Enable (works with 5 volts)
Pin 4= Pseudo Dim pin (i will explaint below)
Pin 5= Panel type selector (options are Samsung, LG and CMI, selected by jumpers in the board)
Pin 6= Same as Pin 5.



Link to the image [URL="https://imgur.com/gcTkPuK"]https://imgur.com/gcTkPuK[/URL]

That board works with a MPS MP3389 controller...

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

I forgot to mention I desoldered the 3.3v inductor and jumped Vin from the power brick connector to Vin in RT8243 and got 5 and 3.3v standby voltages.
My only problem now is 3.3v rail shorted to grownd :v

Re: Trying to find 3v and 5v regulators without schematics... Could it be this IC?

Looks like a common problem. Thanks to this thread i found standby voltages went to zero but in my case short circuit is in one rail and Vin got cut (looks from a burn fuse or some copper got kaput). Can be anything downstream and i don't have a thermal camera.