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Old 03-06-2011, 04:01 PM   #1
freddyfena
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Question HP LP3065 black screen, LED lighted, USB works

Hi
I just got a HP LP3065 from work, because it's non working and out of warranty.
I have tried all 3 DVI inputs and I get no picture, the LED is lighted orange. The computer can sense it's presents and identify the screen. The USB-hub is working. I have googled but with poor results, seem like this is a rather good LCD monitor :-). I have measured the connector of the inverterboard, but it has almost no power, 3-4V somewhere, but no 24V. So I suspect the PSU has failed... for now. I don't see any physical damage or bulged caps. The PSU is a LITEON PA-3171-2-LF rev B. The biggest cap (180uF 450 V) gets very warm and so does the whole heat sink (HS4) with the two transistors and rectifier bridge at the bottom of P1050119.JPG.
I hope some one could give me a hint or point me in the right direction here.
Anybody else have one of these non working?

Best regards
-freddyfena
Attached Images
File Type: jpg P1050119.JPG (1.27 MB, 368 views)
File Type: jpg P1050120.JPG (1.05 MB, 206 views)
File Type: jpg P1050122.JPG (932.2 KB, 185 views)
File Type: jpg P1050123.JPG (486.1 KB, 165 views)
File Type: jpg P1050126.JPG (904.1 KB, 167 views)
File Type: jpg P1050127.JPG (1.53 MB, 140 views)
File Type: jpg P1050128.JPG (1.08 MB, 134 views)
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Old 03-06-2011, 04:19 PM   #2
ecking767
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Default Re: HP LP3065 black screen, LED lighted, USB works

interesting you are getting very little voltage for the inverter board.

one thing you can do to isolate which board has fail, power supply or inverter.

disconnect the cable going to the inverter and then monitor the voltage across the 24v connector on the power supply.

if you get +24 volts then your power supply is OK, if its remain low then you have a power supply problem.
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Old 03-06-2011, 08:49 PM   #3
jetadm123
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Default Re: HP LP3065 black screen, LED lighted, USB works

If you can remove the 4 screws off the cover plate over the heatsinks to expose the rest of the power supply, it would be helpful.
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Old 03-06-2011, 11:52 PM   #4
freddyfena
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Default Re: HP LP3065 black screen, LED lighted, USB works

When I connect only the PSU to 220V, I can only measure the 5V, (3.1 V on the 18V) nothing on the connector to the inverterboard.
Here is another picture.
Thanks so far
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Old 03-07-2011, 04:22 AM   #5
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
When I connect only the PSU to 220V, I can only measure the 5V, (3.1 V on the 18V) nothing on the connector to the inverterboard.
Here is another picture.
Thanks so far
Sorry my instruction wasn't clear, Did you attempt to power on the LCD TV, while monitoring the 24volts?

by connecting a multi-meter to the 24v connector.
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Old 03-07-2011, 04:56 AM   #6
freddyfena
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Default Re: HP LP3065 black screen, LED lighted, USB works

Maybe my mistake, I ment that I had measured it in the first post.
So: At first I measured the Inverter boards connector as all was connected.
and then I removed the PSU board and measured it by it's self. Both measurements gave the same result: 0V on the 24V. There is also another connector with 5V and 18V, but here only the 5V (for the USB) seems to be OK (3.1V on the 18V). There may be other powers/signals as well but I'm not sure what to expect to be correct.
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Old 03-07-2011, 05:42 AM   #7
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Maybe my mistake, I ment that I had measured it in the first post.
So: At first I measured the Inverter boards connector as all was connected.
and then I removed the PSU board and measured it by it's self. Both measurements gave the same result: 0V on the 24V. There is also another connector with 5V and 18V, but here only the 5V (for the USB) seems to be OK (3.1V on the 18V). There may be other powers/signals as well but I'm not sure what to expect to be correct.
This is a common design for the power supplies found on larger displays and TV sets. There is a standby supply which is always on whenever AC power is on. There is a PFC front end, and a main supply which turns on only when the signal (logic) board instructs it. The main supply provides the 18V and 24V.

From the picture of the bottom of the power supply there seem to be two output connectors, although the top pictures only show 1. The one that is shown seems to have the pins labeled, but ironically that information is obscured. For some real good troubleshooting help provide pictures of the connectors that clearly show the legends.

Clue: One of the pins on the connector for the cable to the signal board may be labeled 'PS_ON'. That is the control signal to turn on the main supply. It should be high (> 3 volts).

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Old 03-07-2011, 11:00 AM   #8
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Maybe my mistake, I ment that I had measured it in the first post.
So: At first I measured the Inverter boards connector as all was connected.
and then I removed the PSU board and measured it by it's self. Both measurements gave the same result: 0V on the 24V. There is also another connector with 5V and 18V, but here only the 5V (for the USB) seems to be OK (3.1V on the 18V). There may be other powers/signals as well but I'm not sure what to expect to be correct.
Can you make a measurement with the power supply install and connect all cable except for the inverter cable. Then make a measurement on the inverter power supply connector. Its should read +24 volt.
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Old 03-07-2011, 12:55 PM   #9
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Default Re: HP LP3065 black screen, LED lighted, USB works

Here are the two connectors.
The pin "VON" is 3.1V see picture P1050133.JPG. VBR = 0V
I have connected all but the inverter board and when I measure the 24V it goes up to about 4 V and down to almost zero and up again (Guess I told a bit wrong in the previous post). And still no change with the inverter board connected.

I haven't measured the other connector (P1050146.JPG) when it was assembled because it is completely inside the metal box. If really necessary I will take the time to disconnect all boards and connect them "outside the box. (It's rather awkward to connect the GND cables and the boards to the chassis without the metal box)
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File Type: jpg P1050146.JPG (829.8 KB, 183 views)
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Old 03-07-2011, 01:21 PM   #10
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Here are the two connectors.
The pin "VON" is 3.1V see picture P1050133.JPG. VBR = 0V
I have connected all but the inverter board and when I measure the 24V it goes up to about 4 V and down to almost zero and up again (Guess I told a bit wrong in the previous post). And still no change with the inverter board connected.

I haven't measured the other connector (P1050146.JPG) when it was assembled because it is completely inside the metal box. If really necessary I will take the time to disconnect all boards and connect them "outside the box. (It's rather awkward to connect the GND cables and the boards to the chassis without the metal box)
Good pictures, good information. I'm afraid you're going to have to set this up 'outside the box'. The STBN-24V pins control the main supply. It's pointless to troubleshoot the power supply until you determine if it's getting the 'turn on' signal.

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Old 03-07-2011, 02:17 PM   #11
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Default Re: HP LP3065 black screen, LED lighted, USB works

Thanks, it's a LX3 camera :-)
So, now I have measured again:
I have connected everything without the chassis now.
The STBN-24V pin gives 5.1 V and drops down to 0V and up again to 5.1V, its period is around 5 sec.
VON is 3.3 V and VBR is 0V
Its the same result if I pull out the connector to the inverter board.
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Old 03-07-2011, 04:56 PM   #12
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Thanks, it's a LX3 camera :-)
So, now I have measured again:
I have connected everything without the chassis now.
The STBN-24V pin gives 5.1 V and drops down to 0V and up again to 5.1V, its period is around 5 sec.
VON is 3.3 V and VBR is 0V
Its the same result if I pull out the connector to the inverter board.
That sounds like the processor on the signal card is repeatedly trying to start the main power supply. VON and VBR come from the signal card and are passed directly to the inverter. The 18V output is definitely from the main supply.

I've marked up a few points to test, note the attached picture. The right side of the power supply is Hot. You can encounter voltages as high as 400 volts, so be careful. The other side of the tan line is the cold side of the board.

On the hot side of the board I have circled the leads of the large cap in red and black (Gnd). With the signal card connected and the power supply plugged in, what is the voltage across those pins?

Going back to the cold side, I have labeled the pins of PC501. What is the voltage on the pins I have labeled as 5V and In? Use the point I labeled Cold Gnd for the ground lead of the DMM.

NOW using the - lead of the large cap (circled in black) for the ground lead of the DMM, what are the voltages on the pins of PC501 I have labeled Out1 and Out2? Again, be careful.

I haven't labeled it, but on the top side of the board there is a 16 pin IC near the transformer that was partially covered by the shield. What is that part number?

PlainBill
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Old 03-08-2011, 01:24 AM   #13
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Default Re: HP LP3065 black screen, LED lighted, USB works

Across the large cap I have 380 V
In: alters between 0 V and 5.3 V
5V: alters between 1.3 V and 5.3 V
Out1: 0V
Out2: alters between 0 V and 20 V
The IC is a L6598, See picture also
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Old 03-08-2011, 06:45 AM   #14
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Across the large cap I have 380 V
In: alters between 0 V and 5.3 V
5V: alters between 1.3 V and 5.3 V
Out1: 0V
Out2: alters between 0 V and 20 V
The IC is a L6598, See picture also
Good information. Next question, what line voltage do you use in Norway? 380 volts implies either you are using 270 VAC, or the PFC circuit is working.

The evidence right now is that the controller on the signal board is turning the power supply on, then when it fails to get full power, turns it off, then on again. And the control signal is making it's way through the photo coupler. The bad news is that you will be troubleshooting on the HOT side of the power supply.

Carefully!!! measure the voltage on each pin of the IC. I am particularly interested in the voltage on pins 8, 9, 10 and 12.

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Old 03-08-2011, 03:59 PM   #15
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Default Re: HP LP3065 black screen, LED lighted, USB works

We use 230 V AC in Norway
I have measured on the L6598

Pin 1 = 0V
Pin 2 = 0V
Pin 3 alters between 0.4 V and 2.5 V
Pin 4 alters between 0 V and 2 V
Pin 5 = 0V
Pin 6 alters between 0 V and 0.39 V
Pin 7 alters between 0 V and 0.37 V
Pin 8 = 0V
Pin 9 = 0V
Pin 10 = 0V (GND)
Pin 11 alters between 0 V and 5.5 V
Pin 12 alters between 0.4 V and 11.4 V
Pin 13 = 0V
Pin 14 alters between 0.8 V and 7.3 V
Pin 15 alters between 0.8 V and 7.6 V
Pin 16 alters between 0.5 V and 12.7 V

Last edited by freddyfena; 03-08-2011 at 04:13 PM..
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Old 03-08-2011, 04:27 PM   #16
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
We use 230 V AC in Norway
I have measured on the L6598
Pin 8, EN1 = 0V
Pin 9, EN2 = 0V
Pin 10, GND = 0V
Pin 12, Vs goes from 0.4 V to 11.4 V up and down
230 VAC in and 380V on the large cap says the PFC circuit is working. Very good.

Pin 12 going up and down constitutes a 'smoking gun'. You had mentioned that the period of the STBN-24 line is about 5 seconds. Does the voltage at pin 12 change at the same rate?

C310 is a suspect, it is the filter cap for the supply pin on the L6598. Also, on the attached picture I have circled two dual diodes. What is the resistance between the center pin and either side pin of each diode?

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Old 03-09-2011, 01:57 AM   #17
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Default Re: HP LP3065 black screen, LED lighted, USB works

Yes Pin 12 and STBN-24 seems to have a period of about 4 seconds
The two diodes have a resistance of 407 respective 403 ohms.
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Old 03-09-2011, 06:58 AM   #18
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Default Re: HP LP3065 black screen, LED lighted, USB works

Quote:
Originally Posted by freddyfena View Post
Yes Pin 12 and STBN-24 seems to have a period of about 4 seconds
The two diodes have a resistance of 407 respective 403 ohms.
At this point we get into uncharted territory. If you haven't done so, look up the datasheet for the L6598. When pin 12 is high the power supply SHOULD be working; clearly it's not, and I don't have a clear idea of why not.

I've marked up the picture some more. The red line marks the path of +380VDC to the primary of the transformer. The light brown line marks the ground return line. Of particular interest is a point I've circled with a question mark in the center. That may be the component in heat shrink tubing on the top between the two driver transistors. Check it. Of course, the driver transistors and any diodes and small transistors in the area should also be checked with power off. And yes, the L6598 could also be defective. The input voltage you reported SHOULD be high enough to cause it to start. Of course, check for bad solder joints.

Several points of caution. As I've already pointed out, when power is on you are dealing with potentially lethal voltages. Also, the frequency and amplitude of the signals around the driver transistors may be enough to fry a DMM.

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Old 03-09-2011, 01:24 PM   #19
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Default Re: HP LP3065 black screen, LED lighted, USB works

With out power I have measured the component in heat shrink tubing (a 0.33 ohm resistor) to 0.3 ohm. I have also measured all diodes I could see; all but two had 0.4 - 0.7 V. One, Z0101 is short circuited, 0 ohm and the other D307 (Besides L6598) gives 0.1 V and has 95 ohm, see picture. I've also looked after bad bad solder joints more carefully, but can't see anything bad. I'm not sure how to test the transistors.
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Old 03-09-2011, 01:41 PM   #20
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Default Re: HP LP3065 black screen, LED lighted, USB works

Z? Zener diode... probably shot. They're designed to fail short (although i've blown them in every imaginable way including physically shattering the glass but that's a different story). Lift it out, if it still gets zero ohms change it. Test that other diode too while you're at it.
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