HP L1955 No Video

[conglo]

Re: HP L1955 No Video

maybe the backlight lamps are dead? see anything when you shine a flashlight on the screen?

The lamps are fine. I can see them turn on.

Basically, the monitor works correctly except that there is no video...see the post above this one for the details.

[PlainBill]

Re: HP L1955 No Video

The extra circuit board you're referring to is probably the USB board. This monitor has a built in USB hub.

I don't know if it helps, but I've noticed that there is almost no electrical whine noise anymore since I've changed the caps.

As for what is happening...
The backlights are on, but the screen is black. There is a faint vertical grey bar that is in the center of the screen. I think this is the message text from the monitor saying that there is no signal and then another one saying that it is going to sleep. I can see the width of the vertical bar change as if the message changed. When the monitor was working before, these messages were in white rectangular boxes...one message box might have been a different size than the other.

Does that make sense? If not, I'll draw out pictures of what I mean.

Also, I checked the fuse on the panel board and it's not open. I also measured 5V coming from the logic board. There are three 5V lines and 4 grounds.

EDIT: Forgot to say one thing...
The fade to black I described in my first post, happened about a two weeks ago and I just turned off the monitor and waited a few minutes. When I turned it back on it worked again, but about a week later (when I first posted) it happened again. This time I couldn't recover it just by switching off.

Thanks for the picture. I was getting confused by the ribbon cable to the front panel.

If you can find a spec sheet for the gm5321 chip, I'd make sure it's getting the proper voltages. Off the top of my head, the voltages you mentioned earlier are correct. I would say your best chance would be to find a logic board from a L1955 with a broken screen.

PlainBill

[conglo]

Re: HP L1955 No Video

Thanks for the picture. I was getting confused by the ribbon cable to the front panel.

If you can find a spec sheet for the gm5321 chip, I'd make sure it's getting the proper voltages. Off the top of my head, the voltages you mentioned earlier are correct. I would say your best chance would be to find a logic board from a L1955 with a broken screen.

PlainBill

I've found a datasheet for the Genesis gm2221 which is similar to the gm5321. I've attached it here in case anyone needs it. I've also attached a datasheet for the AU Optronics M190EN03 V0 LCD panel. This is the LCD panel in my L1955.

Now onto my findings...
Using the datasheet, I've checked most of the pins on the gm5321 and they all appear to be correct either 1.8V or 3.3V.
I haven't changed the caps on the logic board. Should this be done? I'm not sure if anyone has ever had a problem with those.

Other than that, I'm not sure what else I can do?
If the voltages on the logic board are correct, does it mean that the LCD panel board is bad?

I wasn't able to find a panel or logic board on eBay.

Anyone have any more ideas?

[PlainBill]

Re: HP L1955 No Video

I've found a datasheet for the Genesis gm2221 which is similar to the gm5321. I've attached it here in case anyone needs it. I've also attached a datasheet for the AU Optronics M190EN03 V0 LCD panel. This is the LCD panel in my L1955.

Now onto my findings...
Using the datasheet, I've checked most of the pins on the gm5321 and they all appear to be correct either 1.8V or 3.3V.
I haven't changed the caps on the logic board. Should this be done? I'm not sure if anyone has ever had a problem with those.

Other than that, I'm not sure what else I can do?
If the voltages on the logic board are correct, does it mean that the LCD panel board is bad?

I wasn't able to find a panel or logic board on eBay.

Anyone have any more ideas?

It could be the panel, but the symptoms you described for the initial failure suggest a failure in the Genesis chip. Others with more experience may have another opinion.

PlainBill

[EGuevarae]

Re: HP L1955 No Video

I've found a datasheet for the Genesis gm2221 which is similar to the gm5321. I've attached it here in case anyone needs it. I've also attached a datasheet for the AU Optronics M190EN03 V0 LCD panel. This is the LCD panel in my L1955.

Now onto my findings...
Using the datasheet, I've checked most of the pins on the gm5321 and they all appear to be correct either 1.8V or 3.3V.
I haven't changed the caps on the logic board. Should this be done? I'm not sure if anyone has ever had a problem with those.

Other than that, I'm not sure what else I can do?
If the voltages on the logic board are correct, does it mean that the LCD panel board is bad?

I wasn't able to find a panel or logic board on eBay.

Anyone have any more ideas?

The KDS K917S (900p) notes I have show that a M190EN03 V.3 is used on that units. I will try to find pictures (I normally take pictures of all the units I take apart). If you research and found that the V.0 and V.3 are interchangeable, you can look for that units. I think I've seen the panel in other 900P units, but I'll have to see my notes.

[conglo]

Re: HP L1955 No Video

I was finally able to get some parts off of eBay.

Turns out that the LCD panel was bad. Once I replaced that it worked.

Now, given what happened to my old panel (fade to black from the sides to the center), is there a way to fix it? What would cause an LCD panel to fade to black from the sides inward?

[PlainBill]

Re: HP L1955 No Video

I was finally able to get some parts off of eBay.

Turns out that the LCD panel was bad. Once I replaced that it worked.

Now, given what happened to my old panel (fade to black from the sides to the center), is there a way to fix it? What would cause an LCD panel to fade to black from the sides inward?

I don't know enough about the technology to do more than hazard a guess. It's a failure of the panel electronics. A common failure is a blown fuse on the circuit board, that usually results in a white screen. Perhaps one of the voltages generated on the panel electronics is missing.

PlainBill

[wanyf]

Re: HP L1955 No Video

How do we test de backlight lamp?

Please help.