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**Krankshaft** · 08-07-2009, 10:07 PM

Re: HP L1955 No Video

Check for bad caps on the inverter and on the video board.

There were Bright Green Lelons on my video board they all went bye bye.

**conglo** · 08-07-2009, 10:17 PM

Re: HP L1955 No Video

I have those caps on my board, but they don't look like they are bad (visual inspection only).

Those caps are on the inverter board. Would they cause the no video problem? I figured it would have to be on the video board. But, of course, the video board looks very good to me.

Do you know what the replacement parts would be for the inverter board?

**Krankshaft** · 08-07-2009, 11:28 PM

Re: HP L1955 No Video

Check for supply voltage from the PSU to the video board.

**EGuevarae** · 08-08-2009, 12:38 AM

Re: HP L1955 No Video

Originally posted by conglo

I have those caps on my board, but they don't look like they are bad (visual inspection only).

Those caps are on the inverter board. Would they cause the no video problem? I figured it would have to be on the video board. But, of course, the video board looks very good to me.

Do you know what the replacement parts would be for the inverter board?

Replace them If they haven't failed yet, they will.

**conglo** · 08-08-2009, 11:38 AM

Re: HP L1955 No Video

Originally posted by Krankshaft

Check for supply voltage from the PSU to the video board.

The voltages to the video board are 1V, 3V, and some 5V. Does that sound right?

I'll also post a pic of the board if you'd like...I'm currently charging my camera batteries.

**conglo** · 08-08-2009, 02:49 PM

Re: HP L1955 No Video

Here are pictures of my inverter board (front and back) and my video board.

I've included a couple of shots in different lighting.

Attached Files

**sofTest** · 08-08-2009, 06:25 PM

Re: HP L1955 No Video

It might be the picture, but it looks like the green capacitor on the lower left side of the picture of the video board might be bulging. As for the inverter, search the forum for 1940, as this model use a inverter very similar to the one you got, and you will find several advices on troubleshooting that board.

**conglo** · 08-08-2009, 07:10 PM

Re: HP L1955 No Video

I've tested some caps (without removing them from the board) and they don't read the correct values. Since I didn't remove them, I'm not sure that my readings are ok or not.

Is it ok to test while still on the board?

Also, since it shouldn't cost to much to replace the caps...
What should I buy for replacements?

I can list the caps currently on the boards if needed.

Thanks.

**sofTest** · 08-08-2009, 07:46 PM

Re: HP L1955 No Video

What did you test for? ESR? Capacitance? You can test for ESR in circuit, provided that you don't have capacitors in parallel on the board. For capacitance, one usually do need to remove the capacitor off the board to get a correct measurement.

A list of make, series, values and physical size will be helpful if you need help on replacements. Also, if you plan to buy from one particular place, tell us where, because vendors carry different make of capacitors.

**Krankshaft** · 08-08-2009, 08:42 PM

Re: HP L1955 No Video

They're Jamicons and Lelons after seeing the pics I remember from their colors.

Tracing out and making sure that the video board is getting supply voltage should be your first step. The rainbow colored connector all the way on the right is from the PSU for the board. At minimum measure across the secondary filter caps on the PSU to check the output voltage.

**conglo** · 08-08-2009, 09:44 PM

Re: HP L1955 No Video

Originally posted by Krankshaft

They're Jamicons and Lelons after seeing the pics I remember from their colors.

Tracing out and making sure that the video board is getting supply voltage should be your first step. The rainbow colored connector all the way on the right is from the PSU for the board. At minimum measure across the secondary filter caps on the PSU to check the output voltage.

Which caps are the secondary filters? Do you know what the voltages should be?

**conglo** · 08-09-2009, 02:59 PM

Re: HP L1955 No Video

Here is a list of electrolytic caps from my PSU/Inverter board...

Code:

PCB#	Brand	Volts	Farads	Diameter	Height
----	-----	-----	------	--------	------
C802	Elite	35V	220uF	8mm		16mm
C801	Elite	35V	220uF	8mm		16mm
C605	Elite	450V	150uF	17mm		50mm
C813	Lelon	50V	33uF	6mm		11mm
C811	Jamicon	50V	1uF	5mm		11mm
C611	Lelon	50V	47uF	6mm		11mm
C606	Lelon	50V	47uF	6mm		11mm
C707	Elite	16V	1000uF	10mm		21mm
C712	Elite	16V	1000uF	10mm		21mm
C703	Elite	35V	470uF	10mm		21mm
C704	Elite	35V	470uF	10mm		21mm
C709	Lelon	10V	1000uF	10mm		13mm
C708	Lelon	10V	1000uF	10mm		13mm

Note: All appear to be 105 degC

Can someone please tell me what replacements I should buy?
I'm in the US, so I'm guessing that DigiKey or Mouser would be the best places to get them.

This board also has always made a squealing noise when the backlights turn off. Will changing the caps fix this?

Thanks.

**PlainBill** · 08-09-2009, 04:51 PM

Re: HP L1955 No Video

Originally posted by conglo

Here is a list of electrolytic caps from my PSU/Inverter board...

Code:

PCB#	Brand	Volts	Farads	Diameter	Height
----	-----	-----	------	--------	------
C802	Elite	35V	220uF	8mm		16mm  P12412-ND FM $.34
C801	Elite	35V	220uF	8mm		16mm    "      "
C605	Elite	450V	150uF	17mm		50mm  Do not replace
C813	Lelon	50V	33uF	6mm		11mm P10320-ND FC $.27
C811	Jamicon	50V	1uF	5mm		11mm P10312-ND FC $.27
C611	Lelon	50V	47uF	6mm		11mm P10321-ND FC $.28
C606	Lelon	50V	47uF	6mm		11mm   "      "
C707	Elite	16V	1000uF	10mm		21mm P12366-ND FM $.59
C712	Elite	16V	1000uF	10mm		21mm    "      "
C703	Elite	35V	470uF	10mm		21mm P10301-ND FC $.72
C704	Elite	35V	470uF	10mm		21mm    "      "
C709	Lelon	10V	1000uF	10mm		13mm P12353-ND FM $.50
C708	Lelon	10V	1000uF	10mm		13mm    "      "

Note: All appear to be 105 degC

Can someone please tell me what replacements I should buy?
I'm in the US, so I'm guessing that DigiKey or Mouser would be the best places to get them.

This board also has always made a squealing noise when the backlights turn off. Will changing the caps fix this?

Thanks.

I've indicated what caps you should use. These are all Panasonic FC and FM series. The part numbers are DigiKey's. The total comes to $4.40, first class shipping will be about $2.00

PlainBill

**conglo** · 08-09-2009, 05:05 PM

Re: HP L1955 No Video

Originally posted by PlainBill

I've indicated what caps you should use. These are all Panasonic FC and FM series. The part numbers are DigiKey's. The total comes to $4.40, first class shipping will be about $2.00

PlainBill

Thank you!

Is there any reason for not replacing the 450V cap?

**sofTest** · 08-09-2009, 05:29 PM

Re: HP L1955 No Video

Originally posted by conglo

Is there any reason for not replacing the 450V cap?

It's seldom anything wrong with that cap.

**conglo** · 08-15-2009, 08:10 AM

Re: HP L1955 No Video

I've changed all of the caps on the PSU/Inverter board, but nothing has changed.

What should I do now?

**PlainBill** · 08-15-2009, 01:15 PM

Re: HP L1955 No Video

Originally posted by conglo

I've changed all of the caps on the PSU/Inverter board, but nothing has changed.

What should I do now?

I'd like an over-all shot of the back of the monitor. There seems to be an extra circuit board and a cable that doesn't make a lot of sense.

This is the first time I read your first post carefully. The symptoms would seem to indicate a problem with the voltages on the panel itself. What do you mean by 'no video'? Black screen or white screen?

PlainBill

**conglo** · 08-15-2009, 01:52 PM

Re: HP L1955 No Video

Originally posted by PlainBill

I'd like an over-all shot of the back of the monitor. There seems to be an extra circuit board and a cable that doesn't make a lot of sense.

This is the first time I read your first post carefully. The symptoms would seem to indicate a problem with the voltages on the panel itself. What do you mean by 'no video'? Black screen or white screen?

PlainBill

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.

Attached Files

**ratdude747** · 08-15-2009, 04:44 PM

Re: HP L1955 No Video

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

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