Finding a replacement MOSFET
I have a faulty motherboard, it doesn't power up when the power switch is pressed. There are a number of faulty caps that I'm in the process of replacing but the only time I successfully powered the board on there was a audible 'crack'. I thought this was a cap venting but I think it has taken out a MOSFET.
I've checked them all with a meter (in place) and one of them seems to be short circuited. I was considering desoldering it and then seeing if the board powers up (even partially). If that's successful I was going to try and track down a new MOSFET. I don't seem to be able to find the exact part here in the UK (NIKO P60N03LDG) but I've found the datasheet. What properties do I need to match to get a substitute? Am I likely to be able to get the board working again or should I just junk it? Thanks, Simon |
Finding a replacement MOSFET
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Finding a replacement MOSFET
I have a faulty motherboard, it doesn't power up when the power switch is pressed. There are a number of faulty caps that I'm in the process of replacing but the only time I successfully powered the board on there was a audible 'crack'. I thought this was a cap venting but I think it has taken out a MOSFET. ** I found then when some 1200uF 6V electros when bad on the MOBO in my previous PC, a mosfet associated with one of them got VERY hot. New electros fixed that completely. I've checked them all with a meter (in place) and one of them seems to be short circuited. ** That is what overheated mosfets do. Am I likely to be able to get the board working again or should I just junk it? ** Worth a go, I'd say. Fitting the new SMD mosfet to the PCB is gonna take some skill and care though. Changing electros is tricky enough. ..... Phil |
Finding a replacement MOSFET
On Sunday, April 6, 2014 5:18:31 AM UTC+1, Phil Allison wrote:
** I found then when some 1200uF 6V electros when bad on the MOBO in my previous PC, a mosfet associated with one of them got VERY hot. New electros fixed that completely. These were 1000uF 6.3v caps. I was hoping the board was salvageable, I'd just fired it up to check that I had a working baseline when it went pop... ** That is what overheated mosfets do. Is this short likely to have caused other parts to fail? ** Worth a go, I'd say. Is removing the dead MOSFET and trying to power up the board a safe thing to do? Fitting the new SMD mosfet to the PCB is gonna take some skill and care though. Yeah, I've only got a 40W iron, the caps came out reasonably easily using a heat gun to pre-warm the board. I was hoping to do the same with the MOSFET. Simon |
Finding a replacement MOSFET
On Saturday, April 5, 2014 11:36:11 PM UTC+1, Maynard A. Philbrook Jr. wrote:
Any way, if do plan on replacing the MOSFET, it's a logic level type which means the gate voltage Vgs(thr) is low. Also it's a 60 Amp continuous part with 12 mohms. So you need that or less. I've a couple of scrap boards, one has P0903BDG and P75N02LDG MOSFETs. I'm assuming the P090's are no good as they're rated at 50A. The P75's have a higher Vgs(th): 1/1.5/3V. Does that rule them out too? |
Finding a replacement MOSFET
On Saturday, April 5, 2014 12:34:12 PM UTC-7, wrote:
I have a faulty motherboard, it doesn't power up when the power switch is pressed. There are a number of faulty caps... I think it has taken out a MOSFET. .... one of them seems to be short circuited. When the MOSFET is replaced, you'll know whether the drive circuit to that MOSFET was also burned up; usually there's a gate resistor (maybe 10 ohms) and an IC with a high-current driver transistor, either or both of those can go out when a MOSFET blows. If it's on a motherboard, the drive circuit is likely to have survived (has low voltage input), but in an AC supply, such drivers will often see high DC voltages in a short, and fry. Trace the gate from that MOSFET, and look for a resistor (with a microscope, probably). |
Finding a replacement MOSFET
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Finding a replacement MOSFET
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