How to fix a HP L1706 (PX849A, HSTND-2F02) by Brett

This LCD monitor came to me with the screen completely dark. A couple of days earlier it was working fine, but then it started to flicker; things only got worse from there, until finally the backlight wouldn’t turn on at all. That was all I needed to hear. Time to crack it open and take a look.

There are four screws on the outside corners, plus if you have them installed, all four of the VESA mount screws in the middle will have to be removed. You’ll also need to remove the three screws that hold the stand on. Two should be visible, but one is hidden behind the top plastic cover- just grasp it by the sides and pull up on it to remove it and access the last screw. The stand should slide out now. Turn the monitor over and carefully peel away the silver bezel. I like to attack this from the inside of the monitor, rather than prying at the edges of the plastic. If you do this, be careful not to put too much pressure on the monitor, remember- we are trying to fix it here. Once removed, flip the monitor over, but hold onto the panel (don’t drop it!), it should fall out and the back should come off now.

Well, now we are down to the inner shell. You’ll need to lift up on that shield thing there (technical term, I know) and carefully unplug the LCD panel cable. Don’t forget to unplug the inverter cables too (needle nose pliers help here so you can grab them by the connectors instead of tugging on the cable and possibly pulling it out of the connector- bad!)

Carefully flip and remove the four screws, two on the left, two on the right, that hold the panel to the inner shell. The panel should lift out. Put it somewhere safe where it won’t get scratched or fall. We’ll need to get the board out to give it the once over, so unplug the cable from the button board for the front controls, then flip the shell up to remove the standoffs from the VGA connector and the screws from the power connector.

Once you get the screws off that hold the QLIF-041 REV A (490421200100R, TCI-AjS, 79042120 _ _ _ _ R written on mine) AIO board (All in one: the power supply, logic, and inverter are all on the same board) in place, it should lift out. Flip it over and surprise! Bad capacitors.

 

Time to dig around… and yes! I have some 25v 470µF replacements in stock. Time to warm up the irons and get to it. Maybe turn the 80’s music up a little… Perfect.

For my monitor, I needed to replace: C864, C862, and C855. From their position on the board, they look like they are part of the inverter circuitry. That would make sense given the symptoms. Clip the bent leads or bend them back up, your choice- I forgot which I did. Once they are straight, the desoldering iron makes quick work of the removal process.

Pop the new caps in (mind your polarity and pardon the pun) and solder them all pretty like. Done? Good. Not too bad. Sure you haven’t done this before?

Hang your irons to cool and don’t forget your OSHA signage. Assemble your monitor, remember to plug in the cables and put the cover thingy in place, or else like me, you’ll be cursing as you take it apart the second time. Comments are always appreciated. Thanks for watching!