Compaq Presario's LCD Monitor Not Turning On: September 2020

After two or so weeks of my recently purchased used Compaq Presario working great, the LCD monitor no longer wants to power-up and turn-on. Remember, I bought this laptop for a really low price of $30 because the motherboard was supposed to be bad.

Testing LCD Monitor: Part 1

In the first video, I forgot to mention that the NI myDAQ voltage meter only measures 20 V_rms for AC voltage; only mentioned the DC voltage. Continuing on, RMS voltage is the DC equivalent voltage that multimeters read when measuring AC voltage. If you multiply the 20 rms voltage by 1.414 or divide it by 0.707, this will convert the AC rms measurement into AC peak voltage which is the reading that you would see on an oscilloscope. Therefore, the maximum peak voltage that the myDAQ voltage meter can read is approximately 28 volts (28.29 volts rounded). Although, you don't use this part of the myDAQ meter when using the oscilloscope which I believe has a max range of +-10 volts peak.

The HP part number for this Compaq Presario motherboard is 623915-001. The Quanta number on the board shows it to be an AX2 design; entire P/N is DA0AX2MB6E1 Rev E. Note: I don't know whether the third character is a zero or an 'O'. It wasn't too difficult to find a PDF schematic for this motherboard, but the boardview ( .brd ) file has proven to be most difficult where I still don't have a working file. The two files that I have, OpenBoardView software gets a runtime error when trying to open them, like it's missing some sort of support file. Currently, I am using an AX1 boardview file found on the Presario CQ42 editions. It is similar but not an exact match. If anyone knows a link to a working boardview file the AX2 boards found in Presario CQ56 laptops, please post a link in the comments below.

In case you are interested, here is a copy for the instruction manual for the NI MyDAQ that I'm using in the video as well as the schematic for the AX2/7 motherboard.

NIMyDAQ_UserGuide.pdf

Download PDF • 1.97MB

quanta_ax2,_ax7_r1a_20091224_schematics_.

Download • 1.04MB

This next file is HP's guide to reset the BIOS for laptops and some desktops.

HPGuide2ResetBIOS.pdf

Download PDF • 372KB

Testing LCD Monitor: Part 2

Testing LCD Monitor: Part 3

In video part 3, I mention that it's only feasible to solder the 128-pin integrated circuit that's used as the management controller device by means of a heat-gun and not a soldering iron. I have since learned that such a feat is possible utilizing a soldering iron. Below is a video from Circuit Technology demonstrating most of the process of doing such a task.

Continuing Progress...More to come at a later time.