HP14 - DA0G7GMB8F0 REV.F

[Darren Hibbert]

Will do but can you show me where Source & Drain are on this chip as it has 2 gates and 3 pins one side and 3 on the other. Thanks.

[mon2]

Sure - see attached. Get a bearing of pin # 1 and locate the belly pads that will be visible on the North and South of the body as shown in the datasheet here:

Pin # 1 = DOT / DIMPLE = Top Left of the mosfet and the first pin is the G1 pin. Then count in a 'U' counterclockwise direction for the rest of the pins.

[Darren Hibbert]

OK thanks for that. 😀

Source to Drain - 43K ohms
Source to Gate 1 - 78K ohms
Source to Gate 2 - 2.4M ohms
Gate 1 to Drain - 1.34M ohms
Gate 2 to Drain - 4.7M ohms.

[Darren Hibbert]

Just found another MOSFET below the one I just measured (with a coil between it) and its exactly the same QA3112

Source to Drain - 1.2M ohms
Source to Gate 1 - 1.5M ohms
Source to Gate 2 - 2.4M ohms
Gate 1 to Drain - 180K ohms
Gate 2 to Drain - 3.6M ohms.

[mon2]

The measurements with kohms are of concern. I would consider to source some spares and replace these parts. You can also flux each (make a note of their location #1 position first); remove off the board and then test each when the parts are on your work bench. Confirm is the measurements remain this low.

[Darren Hibbert]

I took the mosfet off and the readings are reading OL

[Darren Hibbert]

I think I might change the MOSFET anyway. I have some old boards but none of them have a QA3112 on them but I found a board with 22CF FDMS3660S MOSFETs which looks similar. Could you compare them and let me know if they would be suitable? Many thanks.

[Darren Hibbert]

Anyone?

[mon2]

The replacement looks suitable - not as high current drain support as the original but is worthy of testing. Same pinout, etc.

[Darren Hibbert]

Many thanks will give it a go.

[Darren Hibbert]

Well I changed the MOSFET and the laptop is still doing exactly the same!! On and off every 3 seconds. So frustrating.

Is there anything else I can try? I'm determined to get this going.

[mon2]

Do you ever see any text / graphics on the display during the 3 seconds the power is on? You may have a dead CPU.

Remove all power / no battery. Meter in resistance mode (not diode mode). Measure the resistance to ground of each inductor. Checking for a low resistance measurement. Post any suspects.

[Darren Hibbert]

No text and no backlight.

7 inductors on the board.

1 - 0.5K ohms
2- 1.10K ohms
3 - 37K ohms
4 - 0.8K ohms
5 - 0.7K ohms
6 - 0.7K ohms
7 - 36K ohms

[Darren Hibbert]

Board with the inductors numbered.

[Darren Hibbert]

Seems a bit low to me but then I don't really know anything about this.

[Darren Hibbert]

Can anyone help?