hp pavillion vf51

[hpaca509]

Hello everyone this is my first time posting. I am a completer newbie. I read a thread here about how to fix gateway 1975 w monitor and fixed right up. now i have a new challenge. my hp vf51 does not turn on at all. i have check the caps and all looked good. what should i look for next any help will do thanks. hope to be a member of community for a long time.

[retiredcaps]

Re: i have a dead hp pavillion monitor vf51

my hp vf51 does not turn on at all.

Welcome.

First, you posted this in the wrong section. It should be in the Troubleshooting Computer Displays section.

So start the thread in that section.

Also, be more specific about what "does not turn on". Do you see the power LED?

Post clear focused pictures (all boards - top and bottom) after reading

https://www.badcaps.net/forum/showthread.php?t=1868

edit: You can check the fuses. A good fuse should read 0.3 ohms.

[hpaca509]

Re: i have a dead hp pavillion monitor vf51

thank you i will do that.

[hpaca509]

hp pavillion vf51

hello,

total newbie here to this. I have a hp vf51 that wont turn on when you push the power button it doesnt turn on. i put some pics of the back hope i did it all right. any help will do thank you.

[seanc]

Re: hp pavillion vf51

Do you have an ESR meter?

[retiredcaps]

Re: hp pavillion vf51

I have a hp vf51 that wont turn on when you push the power button it doesnt turn on. i put some pics of the back hope i did it all right. any help will do thank you.

First, that is a great clear focused picture.

Second, it helps to tell us that this monitor uses an external power adapter. I only knew this because I saw P500 and then looked up the manual.

Okay, now if you have a multimeter, the first thing to check

1) does your external power adapter provide the correct DC voltage? You should get 12V DC according to the manual.

2) Check all the fuses on the board with power off and unplugged. They should measure 0.3 ohms. I see (thanks to the great pic) FB500, FB501, FB502, and FB503 right by P500.

[jetadm123]

Re: hp pavillion vf51

disregard

[dood]

Re: hp pavillion vf51

Merged the thread from the FAQ's section to here.

[retiredcaps]

Re: hp pavillion vf51

1) does your external power adapter provide the correct DC voltage? You should get 12V DC according to the manual.

2) Check all the fuses on the board with power off and unplugged. They should measure 0.3 ohms.

Assuming 1 and 2 are good, the next step I would take is to measure LM2596 (IC500 - found near upper left hand corner) .

The datasheet is at

http://pdf1.alldatasheet.com/datashe...2596S-5.0.html

On page 2, we see that pin 1-Vin, pin 2-output, pin 3-ground, pin 4-feedback, pin 5-on/off.

Since your chip is says -5, I'm going to assume it is going to output 5V. Thus, we should see 12V DC on pin 1 and 5V DC on pin 2.

Put your multimeter on 20V DC if it is manul range. Black probe in COM, red probe in Volts. Assemble all the boards, put in all the grounding screws.

Plug the ac adapter into the monitor.

Put your black probe on pin 3 (ground). Put your red probe on pin 1. Record DC V reading. Now move your red probe over to pin 2. Record DC V reading.

Be careful not to have the probes slip and possibly short out something.

[hpaca509]

Re: hp pavillion vf51

i have a craftsman digital multimeter.
As i said earlier total newbie....how do i test fuses just put tips on of multimeter and will get 3 ohm reading and if i dont get one are there replacable. Thanks for all the info

[retiredcaps]

Re: hp pavillion vf51

how do i test fuses

To test a fuse, turn off power and unplugged.

Put your black probe in com jack, red probe in the ohms jack. If your multimeter is not autoranging, set it to the lowest ohms (usually 200 ohms).

Put black probe on one side of the fuse. Put red probe on other side. A good fuse should read 0.3 ohms (NOT 3 ohms).

To test your ac adapter, check out this youtube video.

http://www.youtube.com/watch?v=ykq4GJMgpf8

[hpaca509]

Re: hp pavillion vf51

ok so i did all the fuse checks and they are ok. i switched to the next step to check LM2596 pins when i did ground 3 to red one I got a reading of 2.56.
when i went to probe 2 i got zero. once again thank you.

[retiredcaps]

Re: hp pavillion vf51

ok so i did all the fuse checks and they are ok. i switched to the next step to check LM2596 pins when i did ground 3 to red one I got a reading of 2.56.
when i went to probe 2 i got zero. once again thank you.

Okay, test your ac/dc adapter to see if you get 12V DC. It may not be outputting 12V DC. You don't see it, but there are caps inside that adapter that could be bad.

[hpaca509]

Re: hp pavillion vf51

i plugged the red tip into the center of the computer adapter and the black on the side and got a reading of 18.6

[hpaca509]

Re: hp pavillion vf51

did i have to have it plugged in?

[retiredcaps]

Re: hp pavillion vf51

i plugged the red tip into the center of the computer adapter and the black on the side and got a reading of 18.6

Can you post a picture of the ac adapter so we can see the voltage and amps rating on it?

edit: what are the values of C501, C503, C524? It should say something like 1000uF 25V (I'm guessing). This is related to post #5.

[retiredcaps]

Re: hp pavillion vf51

It should say something like 1000uF 25V (I'm guessing).

After re-reading the LM2596 datasheet, on page 1, it shows a typical application. It shows 12V unregulated going to a 680uF cap and then into pin 1 (Vin).

So if the AC adapter is good and the voltage on pin 1 is low, that leaves the 680uF cap as suspect.

Caps don't have to be visibly bloated to be bad. They can have out of tolerance uF and/or high ESR (ohms). Hence the question about the ESR tester in post #5.

If you don't have an ESR tester, the easiest way to test this theory is to replace that cap and retest LM2596 to see if you get 12V DC in.

[hpaca509]

Re: hp pavillion vf51

so here is a pic of the screens power cord. hope this helps came out a little blurry

[retiredcaps]

Re: hp pavillion vf51

so here is a pic of the screens power cord. hope this helps came out a little blurry

Odd. The manual for the VF51 on page 24 clearly says output is 12V DC 3.3A for the adapter. Yet your picture shows 18.5V DC and 4.9A.

Since you measured 18.6V DC, we will assume this is a good adapter.

[hpaca509]

Re: hp pavillion vf51

thank you for your patience and time i will try this and see how it goes where should i go from here? i have kids and they just woke up from their nap. Have a good day and I will try to be on later thanks again Retiredcaps.