HP L1906 "No Signal"

[spoon]

Hey guys,

I recently picked up a HP L1906 LCD Display for cheap because it would not get an input signal. The monitor turns on and it looks like the backlight is fine since the "No Signal" and "Going to Sleep" messages show up bright and clear.

I tore it apart hoping to find some obviously bad caps that could be replaced on the Video Board or even the Power Supply but after a visual inspection they all look fine (no visible bulging or leaking).

Is it possible they are still bad? Would that cause this sort of problem, or would it likely be something with the signal processor chip?

Thanks for the help!

I'll attach some pics of the two boards just in case it's helpful.

[PlainBill]

Re: HP L1906 "No Signal"

Hey guys,

I recently picked up a HP L1906 LCD Display for cheap because it would not get an input signal. The monitor turns on and it looks like the backlight is fine since the "No Signal" and "Going to Sleep" messages show up bright and clear.

I tore it apart hoping to find some obviously bad caps that could be replaced on the Video Board or even the Power Supply but after a visual inspection they all look fine (no visible bulging or leaking).

Is it possible they are still bad? Would that cause this sort of problem, or would it likely be something with the signal processor chip?

Thanks for the help!

I'll attach some pics of the two boards just in case it's helpful.

Pictures always help. In this case, what are the voltages on the three pins of U601 and U602? What are the part numbers of U601 and U602?

PlainBill

[spoon]

Re: HP L1906 "No Signal"

Thanks for the reply PlainBill. I've replaced a few bad caps before but I'm not electronics expert so forgive me if my explanation is a little crude.

Here's what I got for voltages:

U601-
P/N: 1084-33 0603FL
Voltages:
Monitor On:
Legs (from right to left in photo)
1 - 2 = 3.3V
1 - 3 = 5.9V
2 - 3 = 1.8V
Monitor Standby:
1 - 2 = 3.3V
1 - 3 = 5.1V
2 - 3 = 1.8V

U602-
P/N: AZ1117D-L8EI 602J23
Voltages:
Monitor On:
Legs (from right to left in photo)
1 - 2 = 1.8V
1 - 3 = 3.5V
2 - 3 = 1.65V
Monitor Standby:
1 - 2 = 1.8V
1 - 3 = 3.9V
2 - 3 = 2.14V

Also on a related note: When I plugged everything in with the monitor actually taken apart, I was able to hear a 1 - 2 sec. "sizzling" sound coming from the Power Supply board whenever the monitor went from Standby to On. I'm guessing this might have something to do with the problem, but I'm not sure which component is making the noise.

Thanks again for your help!

[PlainBill]

Re: HP L1906 "No Signal"

Those voltages are correct. I don't have a good idea what could be causing the problem, but here are some possibilities, not in any particular order.

0. Not connected to a computer.
1. Video resolution on computer not correct. (Set the video card to 640 x 480, 60 hz).
2. Bad capacitors on signal card.
3. Bad capacitors on power supply.
4. Bad component between input connector and the Genesis chip
5. Bad support component for Genesis chip.
6. Bad Genesis chip.

As far as the sound from the power supply, I suggest using a cardboard tube (the core from a roll of paper towels) as a rudimentary stethoscope.

PlainBill

[UniT3d]

Re: HP L1906 "No Signal"

I've done this recently on an acer. I would like to suggest checking all zener diodes near the vga dsub connector (at least zd208 until zd211) and the BAV99 diodes (d211, d212 and d213).