HP Pavilion vf15 (15" Flat Panel LCD Monitor)

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Nope. I got it from my parents a long time ago and I seriously doubt that they would ever have it worked on... ever. They would just buy a new one.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Here is a better view of the burn. I was having trouble getting a crisp image of the back without getting glare from the flash. I even went to a different room with better lighting and tried without the flash. So i just uploaded a bunch of them. The corner that is shown is the "top-right" corner. So I flipped the board as though it were a page from a book. The burn mark would be right below where you see the IN, OUT, ADJ

EDIT: In the first image, is that thing to the left of the voltage regulator supposed to be a Philips screw (that got melted)? It looks crazy now.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Here is a question:
What is that black thing? (more detail in the image)

EDIT: the resistance across it is zero. I don't know if that is significant, but there you go.
EDIT: there are 2 similar-looking ones on the other side of the board. I don't know if they do the same thing, but they both had solid resistance across them.

The number printed on it is impossible to see in the image, but it's
75B
46 (the six may be an 8 or a B... difficult to tell. doubt it's a B though because it doesn't look like the B in the number above it)

EDIT: Now that i look closer, it seems that there's some black stuff underneath it (between the two solder points) as though it had melted there. It seems like little black blobs, like puddles. But they are very small and there are none of those anywhere else on the board.

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

I was going to ask you to check that ZENER DIODE (ZD904, ZD = ZENER DIODE) if it is shown as shorted circuit. It is the one that got real hot and caused the board to turn brown.
I cannot read the print on the body. I think we found the cause of the problem.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

So what caused it to burn? Was it the endless "mileage" on worn out caps? Or was it simply just too old to carry on and would have had a super nova regardless of the other parts?

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

It can be from over voltage is being applied and it tried to clamp down the voltage from exceeding the Zener voltage, or it just failed. I will have to trace out the circuit to see how it is connected.

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

What is this component? Jumper wire or a resistor? I cannot see it on the top side of the board.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

I have no issue with swapping out the burnt diode. And since I'll already be paying shipping (the majority of the cost), I can swap out the startup cap and those 2 transistors I already pulled out just for good measure.

I'm wondering if there will still be overvoltage or some other problem that will just burn it out again. Would it be possible to get another diode with better specs? or will that just cause problems?

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

What is this component? Jumper wire or a resistor? I cannot see it on the top side of the board.

It's just a bridge (I guess you say the technical term is a jumper wire). The two spots below it are full components, but the one you circled is just a jumper. It jumps directly to the right ("due East")

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

OK, I traced out the ZD904 connection, it is being used to clamp down the spike on the output voltage feeding the inverter output section incase the regulator went out off control. You can remove it for now and apply the power to the board and measure the DC voltage on the two pads of this ZENER Diode so I can determine the Zener voltage, just power it just long enough to see the steady voltage.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Sorry to flood you with pictures, I'm trying to get you some better lighting. I adjusted some things and snapped a bunch more. There's some glare, but it's on another part of the board.

EDIT: Nevermind

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

I believe that is the 7.5V Zener but not 100%. I will have to look at some of my spare board bins to see if I have one of this board.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Well well. I just tested and got 7.66V. I come back to refresh page and you're two steps ahead of me. So does the 75B have anything to do with the 7.5? or was that just a coincidence?

EDIT: Also, it fell apart when I took it off the board. I didn't even pull very hard. That thing really was dead. And the click only happened one time (I'm guessing you expected that that).

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Here is the similar function of ZD904 used in another HP monitor.
https://cdn.badcaps-static.com/pdfs/...9977010163.pdf
Most power supply design does not use this type of setup for protection.
So if you put the transistors back in the monitor should work.
It is probably TPSMP7.5, OR 7.5A.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

So what is the worst-case-scenario if I just leave it (the Zener diode) out?

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

You can leave it off for testing to see if you have other problems with the monitor.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

So I test to rule out any other component failures. If everything looks good, then I'm clear to order and replace the necessary diode and put everything back together. Right?

[budm]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Yes.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

I'm getting a constant 5V. But that is without a load. I'm gonna plug the rest in and see how it goes.

[jdmillard]

Re: HP Pavilion vf15 (15" Flat Panel LCD Monitor)

Success! I plugged it all in, fired it all up, added it as an extended screen to my laptop and it performed flawlessly.

Bud - If you didn't live 11 hours away, I'd buy you lunch my friend. You are an excellent troubleshooter and you explain things well. This has been a great experience for me. The monitor is outdated, but the things I learned certainly are not!