820-2936 PP3V42 being pulled down.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

At 16k ohms, the reading very low. Suggest to replace this mosfet.

Continue to check other mosfets as well in this area.

Hi mon2,

I removed the mosfet Q7030. Resistance between source and gate is showing O.L. But when I check the resistance between the source and gate pads, it is showing 15.1k Ohm.

The remainder of the resistance to ground on Q7030 are as follows :

Resistance between Source and Drain is 5.11 M ohms.
Resistance between Gate and Drain is O.L.

Resistance on the other pads of Q7030 on mobo are
Resistance between Source and Drain is 8 M Ohms.
Resistance between Gate and Drain is 7.8 M Ohms.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

Out of curiosity, could you please help me with the correct procedure to check a mosfet and what readings to expect? I am learning a lot from you. Kudos to you.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Sure, see here:

https://electronicsbeliever.com/how-...-is-defective/

Prefer the table with the resistance check method.

In general a normal mosfet will be with HIGH resistance values of hundreds of Kohms or more.

It is possible that other parts interconnected with the mosfet are causing the mosfet to appear to be shorted. For this reason, a good sanity check is to remove the mosfet off the board -> allow it to discharge (you can short the pins with a wire - so source & drain; source & gate for example) -> then check again on your work table.

At ~15kohms, the resistance is considered to be too low and likely to be defective. Reverse the meter probes and check again to see if the readings change but would suggest to replace this mosfet.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

I think I confused you. The 15.1 Kohms resistance did not come from the mosfet but from the pad on the mobo where it was installed. The reading came by checking the pad on the mobo after removing the mosfet.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

The resistance between source and gate on Q7030 is showing O.L.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Yes, thanks for the clarification. Continue to check the other combination of pins on this removed mosfet on your work table.

source & drain
source & gate
gate & drain

If each is with a high resistance reading then this mosfet is ok.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

Resistance between Source and Drain is 5.11 M ohms.
Resistance between Gate and Drain is O.L.
Resistance between source and gate is showing O.L.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

This mosfet is fine and not shorted.

Continue to check the low side and also the battery mosfet using the same procedure.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

Readings after removing and checking Q7035

Resistance between Source and Drain is 5.11 M ohms.
Resistance between Gate and Drain is O.L.
Resistance between source and gate is showing O.L.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Q7035 is ok.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

would you like me to remove Q7055 and check it as well.?

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Remove all power and test the resistance while onboard first. Same as earlier.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Here are the readings from Q7055.

Resistance between Source and Drain is O.L.
Resistance between Gate and Drain is O.L.
Resistance between source and gate is showing 16.43 M Ohms.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

This mosfet is not shorted.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

So I think it is safe to say that ISL6259 could be the culprit.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

Yes, it is looking that way. Has this part been replaced already? If yes, reflow it with flux. If not, replace it and test again. Still keep the fuse at the output off the logic board till the PPBUS_G3H is confirmed to be within range.

[bridges_4u]

Re: 820-2936 PP3V42 being pulled down.

Hi mon2,

I have already ordered the ISL6259 and is in transit. It leads me to think that the batch of ISL 6259 i had is from a bad batch as all of them has not yielded any results across different boards.

[mon2]

Re: 820-2936 PP3V42 being pulled down.

That is sad to hear and the parts may be fake but of course continue with the review and update this thread. From the videos by Louis, he said these parts break often on the logic board. You can try to flux and reflow the part as well. Be sure that pin #1 orientation is correct.

Perhaps you can post a close up picture of this part on your board for a review?

[bridges_4u]

Hi mon2,

mon2

Just wanted to give you an update on this as well. Now I have 3.420 volts at pp3v42_g3h and ppbus_g3h is now 12.45volts.

Any suggestions?

Regards

[mon2]

PPBUS_G3H is too low and should be 12v6. This is controlled through SMC over the I2C bus. Confirm the voltage to ground of the SDA / SCL lines that mate with the ISL chip that is building the PPBUS_G3H rail.

820-2936 with 12,23V on ppbus_g3h | Rossmanngroup Forums