Asus PTGD-LR

[Th3_uN1Qu3]

Re: Asus PTGD-LR

• Pins 6 and 7 on the MOSFET close to the same connector are shorted. I removed it from the board and found the MOSFET pins are not shorted, but the tracks on the board are shorted. Pin 6 is Power Ground, and Pin 7 is SW, which the datasheet says is "This pin is connected to the buck switching node, close to the upper MOSFET’s source. It is the floating return for the upper MOSFET drive signal." Is this ok?

I wanted to get some feedback before replacing the transistor again to see if the bad cap was the problem.

Lift the switcher IC off the board and check its pins then the board again. I believe the IC itself has failed short. The 1R0 resistor is most likely the gate drive resistor, if you can't measure it just jumper over it, it isn't really necessary. But do that after you get a reading on that IC.

[sceva]

Re: Asus PTGD-LR

Lift the switcher IC off the board and check its pins then the board again. I believe the IC itself has failed short. The 1R0 resistor is most likely the gate drive resistor, if you can't measure it just jumper over it, it isn't really necessary. But do that after you get a reading on that IC.

Is the "switcher IC" the MOSFET I removed from the board? It is still off, and it has no continuity between pins 6 & 7 off the board, while the pads on the board where pins 6 & 7 attach still have continuity.

I also noticed that the coil (or is it an inductor) nearest the removed transistor tests at .19 with my ESR meter. All the other coils test .00. I don't think this could cause the short, but could it be a problem? I attempted to remove it, but was having trouble getting it hot enough to soften the solder so I left it alone for now.

[Th3_uN1Qu3]

Re: Asus PTGD-LR

Is the "switcher IC" the MOSFET I removed from the board? It is still off, and it has no continuity between pins 6 & 7 off the board, while the pads on the board where pins 6 & 7 attach still have continuity.

Nope, i was talking about the controller IC you mentioned in the pic, the ADP3418K (there's a typo in your pic). Lift it off the board and measure it. If you don't know how to do it with just a soldering iron, it's easy. Put a lot of solder on all pins of one side of the chip. Heat up the big blob of solder while using a small screwdriver to lift that side of the IC up. Do the same for the other side. Use desoldering braid or flux and a desoldering pump to clean the mess after you're done.

Btw, coil is a more non-technical term for an inductor. They mean the same thing.

[sceva]

Re: Asus PTGD-LR

Nope, i was talking about the controller IC you mentioned in the pic, the ADP3418K (there's a typo in your pic). Lift it off the board and measure it.

My mistake, I was calling it the wrong thing. I have done as you said and the ADP3418K is not shorted, but the board still is... I have looked around a bit, but I have not been able to figure out where the short is... I do remember something about testing inductors with the ESR meter, but I don't remember what a "bad" reading would be...

[Th3_uN1Qu3]

Re: Asus PTGD-LR

Leave it off the board for now. I'm quite sure that the board has at least two phases - look for another ADP3418K and see if the board is shorted there too. If it is, chances are this is not your problem. I'm quite sure the inductors are fine too. If anything, they'll heat up more than they should, but that's something we can address later.

In retrospect, if the IC were shorted, the board wouldn't run at all because the processor wouldn't get power. I'm confused about another thing you mentioned in the pic - you said the 1R0 resistor reads 1 @ 200M. If you were REALLY talking about the 200 megohm range, well, that resistor is open or very close to it! It should read ONE OHM!!! If it reads anything else that one ohm, jumper over it, put all parts back in and see what happens.

[sceva]

Re: Asus PTGD-LR

Leave it off the board for now. I'm quite sure that the board has at least two phases - look for another ADP3418K and see if the board is shorted there too.

I found 3 other ADP's, they all showed shorts on 6 & 7. I removed the one closest to the failing MOSFET and the tabs on the board are shorted, not the ADP's pins.

In retrospect, if the IC were shorted, the board wouldn't run at all because the processor wouldn't get power. I'm confused about another thing you mentioned in the pic - you said the 1R0 resistor reads 1 @ 200M. If you were REALLY talking about the 200 megohm range, well, that resistor is open or very close to it! It should read ONE OHM!!! If it reads anything else that one ohm, jumper over it, put all parts back in and see what happens.

I tested 1R0 again. With meter at 2k it reads .002, then nothing as I turn the dmm meter higher, until I get to 200M, and then it reads 1.

If/when I put all the pieces back together and jumping 1R0, and try again, is there anything I can check in the few minutes that it is working?

Thanks for everyone's help!

[Th3_uN1Qu3]

Re: Asus PTGD-LR

The 1R0 resistor reads what it's supposed to then. This is getting difficult... I'd check all other 1R0 resistors that are near the mosfets' gates, it's possible that one of them is open and the mosfet you replaced has to switch more current than normal thus causing it to fail.

As a last resort i'd swap the ADP3418Ks around and see if the failure moves in another area. I'd also test the mosfets with a temperature probe (or your finger but be careful), so you can shut it down before the things blow up.

[PCBONEZ]

Re: Asus PTGD-LR

Have a good snap-shot of the CPU/VRM area without the heat-sink blocking views?

You either have two Phases with two Toroids each [which is odd] or 4 Phases [which I don't see enough MOSFETs for].

You can check values of component in one Phase to the components in the other Phase. If they are the same then it's less likely something is broken.
[Would have helped a lot with that resistor reading.]

.

[sceva]

Re: Asus PTGD-LR

The 1R0 resistor reads what it's supposed to then. This is getting difficult... I'd check all other 1R0 resistors that are near the mosfets' gates, it's possible that one of them is open and the mosfet you replaced has to switch more current than normal thus causing it to fail.

As a last resort i'd swap the ADP3418Ks around and see if the failure moves in another area. I'd also test the mosfets with a temperature probe (or your finger but be careful), so you can shut it down before the things blow up.

I only find one more 1R0 up by the MOSFET that is on the top edge of the board, and it tests .002 like the other one. I am thinking about removing the rest of the ADP's and see if one of them are shorted...

Have a good snap-shot of the CPU/VRM area without the heat-sink blocking views?

You either have two Phases with two Toroids each [which is odd] or 4 Phases [which I don't see enough MOSFETs for].

You can check values of component in one Phase to the components in the other Phase. If they are the same then it's less likely something is broken.
[Would have helped a lot with that resistor reading.]
.

Here are the pics. There are 4 MOSFETS. I don't know anything about Phases... sorry about the resistor mistake. I should have looked up what 1R0 meant and then tested.

[seanc]

Re: Asus PTGD-LR

Is D25 ok - to the left of R397?

[PCBONEZ]

Re: Asus PTGD-LR

You have two Phases.
See that APD3180 over by large cap at RAM slot?
That 'reads' the VID from the CPU and 'tells' the two MOSFET driver [aka controller] chips [the APD3418K in this case] by way of a PWM signal what voltage to keep the Vcore voltage at.

Each APD3418K controls two MOSFETs.
- One high side MOSFET between +12v and Vcore.
- One low side MOSFET between Vcore and ground.
Most designs only use one Toroid on the Vcore output of the MOSFET pairs but yours seems to have two.
-
Each Controller/Driver IC with it's associated High and Low MOSFETS and the Toroid comprises one Phase.
The Phases, as units, operate in parallel to power the CPU.
-
Other VRM variations you might see. [On other mobos.]
- Number of Phases can be 1 to 8 with 2 to 4 being most common after socket 370 era.
- High side MOSFETs [in one given Phase] can more than 1 with 1 being the usual, 2 is common, more is unusual.
- Low side MOSFETs [in one given Phase] can more than 1 with 1 or 2 being usuall, 3 or 4 common, more than 4 unusual.
[One High and two Low in each Phase is pretty common.]

Toroids are the doughnut and rod shaped wire wrapped 'coils' you see.
*Usually* the input [to VRM] Toroid is a rod shaped part near the "P4" 4-pin PSU connector. *Usually* there is one doughnut shaped Toroid in the output of each Phase.
That is usual but they can use other types in either place.

Here is the reference drawing for the APD3180.
https://cdn.badcaps-static.com/pdfs/...5a7e781990.pdf
See figure 4. - If you remove the third Phase and Q3 and Q6 it is basically what you have on this board.

I was working on this for something else but it applies here...
[See attached drawing.]
.

[sceva]

Re: Asus PTGD-LR

Is D25 ok - to the left of R397?

I think so, in diode mode on dmm it reads open ciruit one way, and .22 the other way. I think the correct data sheet shows:
BZX399-C2V4, VR = 1 V, 0.2 uA max.

You have two Phases.
See that APD3180 over by large cap at RAM slot?
That 'reads' the VID from the CPU and 'tells' the two MOSFET driver [aka controller] chips [the APD3418K in this case] by way of a PWM signal what voltage to keep the Vcore voltage at.

Each APD3418K controls two MOSFETs.
- One high side MOSFET between +12v and Vcore.
- One low side MOSFET between Vcore and ground.
Most designs only use one Toroid on the Vcore output of the MOSFET pairs but yours seems to have two.
-
Each Controller/Driver IC with it's associated High and Low MOSFETS and the Toroid comprises one Phase.
The Phases, as units, operate in parallel to power the CPU.

So the problem could be in either Phase... Doesn't help in trying to figure out where to look... I am going to remove the other ADP3418k's and see if one of them are shorted... If I find nothing wrong, I will reasemble everything, turn it on, maybe take a couple of voltage tests and temp checks and turn it off quickly!! I have made such a mess of the board I am not confident that even if I found the problem I will be able to clean it up enough for it to work over the long term...

I was just looking at the pics I uploaded - I took the board outside to get the best lighting - and just realized I need to get a lot more light on my workbench!! I can see things better in the picture than on my table...

[sceva]

Re: Asus PTGD-LR

Got it put back together and turned it on... and.... it booted up again. I have a temp probe and I was checking the MOSFET that burns up, and the top one. They both rose steadily, and when the one that burns up got to 120 degrees I turned it off. I had not checked to see what the operating temp is... I just looked and it says 175 C, which I think is 347 F, so I guess I can let it run a bit longer next time. If it would help to get voltages I will have to rig something up as my probes won't fit in there...

[seanc]

Re: Asus PTGD-LR

strip some wire, leaving only a short amount exposed - you don't want to create a short, solder it in. Strip the other ends back, attach to probes via croc clips, tape, whatever.

[sceva]

Re: Asus PTGD-LR

Victory... well at least some better information.

Forgot to mention this in the previous post, but I removed all the ADP3418k's and none of them were shorted. It looks like that reading may be ok, see below for more detail.

The first leg of the failing MOSFET has higher voltage than the others. See pic for other details. Also in the pics where I am showing that pins 6 and 7 are shorted, well when powered on they are not! And it looks like pin 7 goes to the 3rd leg of the MOSFET. I updated my drawing with more detail. Is it possible that pin 7 goes to both pin 1 and 3 of the MOSFET? I could have misread something...

The docs say pin 1 is the gate, pin 2 is drain, and pin 3 is the source on the MOSFET. The resistor between pin 1 on the mosfet and pin 7 on the IC says 822, and reads 8.29k ohms.

I am only leaving the computer on for a minute or two at a time so hopefully it won't blow the MOSFET for while.

I hope this info will help someone, as I don't understand enough to know what to do next... But I do have a little more hope that we are getting closer to the solution.

[PCBONEZ]

Re: Asus PTGD-LR

.
Here:
I cleaned up the reference drawing I linked to earlier so maybe it will make more sense.
.
The problem may be a bad PWM signal or one of the Sensed signals is wrong to/from the main Controller IC - APD3180.
.

[sceva]

Re: Asus PTGD-LR

First of all, thanks for everyone's input. If you think this is more trouble than it is worth, just say so.

I cleaned up the reference drawing I linked to earlier so maybe it will make more sense..

Thanks. I am slowly gaining some understanding, and your diagram is similar to the one I saw in the ADP3180 datasheet. Seeing something multiple times helps it to sink into my brain...

The problem may be a bad PWM signal or one of the Sensed signals is wrong to/from the main Controller IC - APD3180

Are you saying the higher voltage on the failing MOSFET is a problem?

I was able to get a few more readings before the MOSFET failed (once again), the details are in the attachment. The only odd one was PWM 1 was a bit higher than the PWM 2-4. PWM 1 is the one that connects to the ADP3418 that is controlling the failing MOSFET.

If the ADP3180 is bad, I will have to consider if my skills are good enough to resolder something like that, or find someone local to do it for me. I have seen the videos at Curious Inventor on how to do it, but haven't attempted it myself.

The MOSFET was not that hot, maybe 130 F when it failed this time. And the voltages seem to be within the range on the specs. Does it have something to do with it being in Phases and this one being different than the other ones?

[PCBONEZ]

Re: Asus PTGD-LR

The odd voltage is at least a symptom of 'the' problem.
What I mean is the fact that they are different between Phases.
Hard to say which one is wrong at this point...

I gather it's the upper MOSFET in Phase 1 that is burning out? [Q1 in my sketch]
The lower MOSFETs should not have +12v on any pins. [Q2 in my sketch]
[Phase 1 is associated with PWM-1.]

The ADP3180 itself may or may not be the problem.
There is a sundry of small resistors, diodes and caps in the circuit.
A bad feedback [Sense] path would also cause a bad output because the IC 'sees' and corrects for the wrong value.

PWM-3 and PWM-4 are not used in a 2 Phase VRM.
- Curious that PWM-2 has the same voltage as the unused PWM pins.
Possible that Phase 2 is not working at all and Phase 1 has a double load on it.
Higher voltage might be an attempt by the IC to get more current through the one working Phase.

Should note the a PWM signal is not a DC voltage, it is a square wave.
The width of the Pulses controls how long the MOSFETs are on and/or off.
A DMM only 'sees' the average value of the square wave.
[If it's 1.2v 50% of the time and 0.4v 50% of the time a DMM will read 0.8v.]
Problem is if something is broke then you may actually have DC instead of a square wave.
- Meaning the 0.8v or 0.6v you saw may steady at that 100% of the time. - And the MOSFET is 'stuck' either on or off.
An O'scope is the best tool to tell for sure but a DMM that reads frequency might do the trick.
If neither is possible then knowing DC volts is better than nothing to work with.
Just sacrifice a cap to the great MOSFET God to ensure they are actually switching. [Don't use a Fuhjyyu. That just pisses him off...]

.

[sceva]

Re: Asus PTGD-LR

The MOSFET that is burning out is the one the is connected to pin 7 of the ADP3418 that is connected to PWM-1.

Are the SW1-4 the sense circuits? I haven't tried testing any of these...

Actually I am beginning to look around for a replacement motherboard... I can get an exact replacement for about $75 on eBay, or a new model for about the same thing...

[shovenose]

Re: Asus PTGD-LR

Dont give up! Lol i would give up after replacng the caps and it not working. I would just buy a new mobo

Ps: (unrelated): i know someone who modified his lga775 and runs an amd dualcore