Help needed in repairing my Sun Blade 100 – I can't identify an exploded IC.

[CircuitBored]

Hi all,

This is my first post here – seems like a nice place!

Earlier this week I fired up my Blade 100 for the first time in a while and for some reason my hard drives were not spinning up. I tried the optical drive and that didn't work either.

I tested the voltages on the Molex power connectors and 12V was correct but 5V was reading 1.9V and 0.9V under load. I traced the voltage back through the riser board and quickly found this rather exploded chip, U2.

The input of this chip reads correctly at 5V but the output is, again, 1.9V. Something has obviously gone badly wrong. Sadly I cannot read the silkscreen on the chip any more as it has disintegrated so badly. It's definitely a Fairchild component and I'm fairly sure it's some sort of voltage regulator but I have no idea which one.

I would hugely appreciate it if a fellow Blade 100 owner could open up their computer and identify this chip for me. I am simply at a loss otherwise. There are almost no pictures of these Suns online so my hunt for pictures of this board were entirely fruitless.

A huge thanks in advance to any one who helps me out with this!

All the best,
P

 

[Elf]

I am not certain -- I only have a Blade 150, which I could check if you like, but it may not be the same -- but the layout of the traces to that package make it look a lot more like a MOSFET rather than a voltage regulator. The two sets of tied pins with thick traces (Drain, Source) and the small trace for the Gate are a bit of a giveaway. The prefix on the part also seems to line up, see attached data sheet.

The datasheet attached is not necessarily the same part, but it is representative of the type of part I would guess that this is.

 

[CircuitBored]

Dear @Elf,

Thank you very much for your reply. The datasheet that you sent does indeed seem to have the right pinout but I agree that it's likely not exactly the right part! If you could check the U2 chip on your Blade 150's riser board then I am fairly confident it will steer me in the right direction. Some of the characters on the burnt out chip are just about legible so I can still check for a partial match. Failing that I can check the datasheet for whatever chip is in your 150 and see if it logically makes sense for the 100 as well. The 150 and the 100 are very similar so I wouldn't be surprised if the riser boards were identical.

Please do take a look at U2 on your Blade 150 if you can find the time! It would be hugely appreciated.

 

[Elf]

Certainly; U1 and U2 on the riser (of a Blade 150) appear to be the same FDS4435 P-ch MOSFET, no longer normally stocked. However, the SI4435DY appears to be a compatible equivalent, though you should take care to judge this for yourself. The use of a P-ch MOSFET makes sense for something doing high-side switching to power towards drives, etc.

You should also consider what might have melted the part in the first place. I would check for shorts on the load side?