HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

[momaka]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

^ What piernov said above: if a high-side MOSFET goes, the CPU/GPU may have gotten damaged. I find older hardware is usually more likely to survive high-side shorted MOSFETs than newer stuff (I had a Pentium 4 CPU survive 5 short-circuits on a high-side FET on a mobo I was troubleshooting... and it still worked afterwards ). Same goes for a few older GPUs as well.

That said, it is also possible that your CPU may have been bad/damaged to begin with, causing the failure you saw after replacing the controller.

Either way, when replacing a buck regulator controller, I also always check the surrounding connected components, like any SMD resistors, capacitors, and diodes (especially any boost diode(s) along with Gate-drive resistors, if any).

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

I checked the FETs prior to replacing the IC and they were fine...could've been a busted CPU all along, though it DID turn on without doing anything. Now it just went on and then off with the FETs shorted.....any "clever" way of testing a CPU ? I may not have a similar one on hand, plus I risk damaging that one too. For some reason this board refuses to power on without the CPU installed so I can check the voltages and stuff with no CPU in place....this is getting kinda expensive TBH I can see why Louis Rosmann only fixes Macs...

[momaka]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

No easy way to test the CPU that I know of.

You could do a little "experiment" and connect the V_core (VRM output) of another mobo to this one (with very thick wires, like 2-5 strands of 14 AWG solid copper wire) and see if the CPU can take V_core voltage without frying. But be prepared for possible fireworks and also damaging your other mobo.

I've done this a few times with video cards, but only when I was bored and just didn't care anymore (clearly not on a customer's machine ). I also have lots of "dead"/RROD Xbox 360 motherboards at my disposal. A few have their GPUs removed, so I used the GPU V_core (about 1.0-1.2V on most Xbox 360's) for this experiment. The GPU V_core on the Xbox 360 is pretty well designed and will shut-down from a short-circuit or bad part without getting damaged.

But all in all... nah don't try this, really.
You'd also have to remove all of the MOSFETs from the CPU VRM to do this (or the coils/inductors) - more work than it's worth, most of the time.

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

more work than it's worth, most of the time.

Yes...

I WAS thinking of something crazy like this (it's my MOBO and I don't care): power the CPU externally with a supply...how much power does that thing eat ? The wattage tells me the current figures, so it's it's powered at 1 volt (let's round it off) and it's a 60w TDP CPU that's 60A worth of current which none of my bench supplies can provide. Even if I try it anyway, the current would rise, hit the threshold of the supply and I wouldn't be able to tell if the CPU is shorted or drawing current naturally and normally. The noise on the supply would likely be too great to allow a CPU to run, so it's not a good idea all in all....

[mcplslg123]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

I find this too risky to try-Not worth doing such experiments.

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

True that...

[momaka]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

Meh. When you have decent hardware that you just can't get working or sell for decent scrap price... I say F-it/YOLO!!! and just try something silly. Might as well entertain myself with it at that point. (Any fans of PhotonicInduction or Electroboom? )

... but again, maybe not with a customer's machine.

The wattage tells me the current figures, so it's it's powered at 1 volt (let's round it off) and it's a 60w TDP CPU that's 60A worth of current which none of my bench supplies can provide. Even if I try it anyway, the current would rise, hit the threshold of the supply and I wouldn't be able to tell if the CPU is shorted or drawing current naturally and normally. The noise on the supply would likely be too great to allow a CPU to run, so it's not a good idea all in all....

Exactly, lots of current. Hence why I suggested you'd need at least 2-5 strands of 14-12 AWG wire for the V_core alone... and keep it short (otherwise, losses may drop that 1V too much).
Noise probably won't be an issue, since both boards have caps filtering the CPU.

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

Any fans of PhotonicInduction or Electroboom?

Me...both of them

I'll try replacing the trannies anyway to see what happens...I don't have any other voltage source on hand to test that CPU, plus it's likely junk anyway, so YOLO Yeah, no way I'd do that for a client, but since this one is mine......wattevah

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

Well guys, believe it or not I dug out this hunk of junk again. The reason I bother with it again is because I just performed a successful MB swap on another laptop (an Acer which I also wrote about and gave up on) and thought this one was decent enough to try and resell as well.

Instead of getting the board of Ali like I did for the Acer, I thought I should first check the listings to see if there's one up for sale locally and I came across one which claimed to be in working order at a decent price, so I got it. Trouble is it doesn't work It's not the same exact board, but should be close enough to be compatible with the case and the display. The schematic is different too, so I attach it here.

I have no idea if the guy scammed me and the board was dead to begin with, or if my CPU is dead and won't let the board fire up. If you scroll down and read the original story of this laptop, a pair of transistors on CPU_VCORE blew up, so it's possible some adapter voltage leaked into the CPU and killed something...

I hit the power button - nothing happens. I do get 3.3v on the button itself, as well as 5v for the lid sensor and the current consumption of the whole thing goes up to around 26mA, but nothing else happens. It could be my CPU is defective in some way, so I'm going to get myself a cheap "Arrendale" i3 just to try it. If it still doesn't work, that means I'm not getting CPU_PWEN out of the ITE chip for some reason. Could a faulty BIOS cause a totally dead machine ???

[Dannyx]

Re: HP Pavilion DM4 6050A2402401 Motherboard no CPU Vcore

Ok, turns out I was right: there WAS something wrong with the CPU after all, because I tried a replacement one and the replacement board works now.

As a curiosity, I tried replacing the two MOSFETs and the controller IC again, this time making sure to solder everything as best as I can, but sadly the same thing happened: as soon as I applied power to the DC in jack, I saw the current spike to 15a (the maximum my power supply can put out). I quickly pulled the plug and the FETs were dead again, so at this point I gave up and just binned the board, since it's like the third time I try. Don't worry, I used a second CPU - not the one I managed to fire up the "good" board with.

Makes me wonder what the hell's breaking down each time...