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I disassembled an Asus A7S-A1 2 nights ago for a BGA reflow. Following reflow I inserted a stick of RAM, had the heatsinks re-seated with fan, attached the power button to motherboard and then connected the battery to test if reflow attempt was succesfull... good so far but heres where it all went wrong, lastly I connected the display data/video cable to the board, and a faint pop then burning smell and now no power AT ALL, no post, nothing.

Obviously I should have had everything connected AND THEN lastly the battery.

Anyway thats where I am now. It wasn't the inverter because the loogicboard would still get power im assuming and fans would still spin up etc...so I am guessing that its something on the motherboard (possibly around where the display connects as that is where burn smell seems to be)

What should I be looking for exactly? I realise its, "look for something burned", but anyone know specifically? I can't visually see anything burned.

Should there be some kind of embedded fuse perhaps?

For the record I have a solder station, multi-meter etc...and am not afraid to dig in.

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reported a faint pop and burning smell at the display connector after a BGA reflow, and suggested the reflow could have caused a short. A systematic isolation-and-measure approach will find the fault fastest and with the least risk of further damage.

  • Safety first: remove battery, unplug the adapter, discharge caps where possible and use ESD precautions.
  • Confirm the adapter voltage at the barrel plug with a DMM. With everything disconnected from the board (HDD, optical, LCD/inverter), try powering the board from adapter only.
  • Disconnect the LVDS/display cable and the inverter/backlight harness; if the board then shows any activity the display or inverter/cable is the likely short.
  • Find the input SMD fuse (often marked F or a fusible resistor near the DC jack) and check continuity. Measure DC-in on the motherboard before and after that fuse.
  • With power removed, measure resistance between main input rail (after the fuse) and ground. A very low ohm reading indicates a shorted component. Use DMM diode mode to check MOSFETs, diodes and large electrolytic caps near the input and around the display connector.
  • Check standby rails (3.3 VSB / 5 VSB) at the power-button header or EC power pins. If standby is absent the fault is upstream in the input/regulator stage.

If you detect a hard short, use a current-limited bench supply or a series lamp to limit current while you power the board briefly and feel for the hot component; a thermal camera or freeze spray will help pinpoint heating parts. CCFL inverter circuits carry high voltage—keep the inverter disconnected while troubleshooting. Replace only verified blown fuses, MOSFETs or regulator ICs with correct parts and repair any damaged traces. Start by isolating the display/inverter first; if no standby rails remain with the display removed, concentrate on the DC-input/power-regulator area.

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Member Avatar for Rik_

What exactly do you mean by BGA reflow (I know reflow refers to solder reflowing)? Need to know exactly what you have done to the mobo!
I also repair electronic items so may be able to help with more info!

Member Avatar for bobbytomorow

Hey Rik,

BGA stands for ball grid array, most GPU's are BGA's and thus attached to the motherboard rather than being on a separate board and plugged in like say a MXM board. What happens is that after heating and cooling (expanding and shrinking) they lose contact ith the motherboard and require a reflow. This is very common with Nvidia GPU's and especially 8400 and 8600's.

I have reflowed a few notebooks, typically I will add a copper shim to keep them from separating off the board once repaired but in this case I did not as it did not require a shim, the copper heatsink made good contact.

I hope that helps some.

Member Avatar for Rik_

It's possible the reflow has caused a short!?!

Member Avatar for bobbytomorow

Thats a possibility, albeit slim, like I mentioned I heard a faint pop when I connected the display to the logicboard so I am thinking that is what caused the short. There was also a faint burn smell near the area when the display connects to.

I tore down the cooling assembly and (heatsink/heatpipe/fan) inspected the area around the gpu, where I reflowed and did not notice anything.

Member Avatar for Rik_

Hmmm, it's gonna be hard to find the problem I suspect!

Member Avatar for bobbytomorow

any pointers on where to start checking with a volt meter?

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