Quote from: MrTeal on January 02, 2014, 05:05:41 PM

Remove the chip again, and check the resistance on the 3.3V rail. If it's below about 10 ohms or so, something is shorted and that's what keeps blowing the ST1S10.

Shorts on a main power rail like that are a huge PITA to debug. Depending on what you have available, there's a couple ways to find out what the issue is. The easiest way I know is to hook a lab supply at 3.3V up to 3.3V rail and turn the current limiting down. Grab an IR camera, and turn up the current until you see a hot spot. You can do the same with an IR thermometer, but it's more time consuming. A finger work too, but you need get the problem a lot hotter that way, and if it's something that's a QFN or one of the ASICs you might never notice it get hotter.

Without a current limited lab supply, it becomes more of a crapshoot. It's probably not worth trying to debug yourself if that's the case.

Yup. However the 3.3 volt supply on a jalapeno is really pretty small. Even the 1 volt supply will just crowbar and die if shorted (verified on the danger board); what blows things up in the FET world is when the FETs short due to overheat on high loads. Then if you feed it from an unlimited 12 volt supply (as opposed to the little supplies BFL sends) then the weakest component will explode.

That's why I have been recommending putting a 7 amp fuse in series with your jally when running it on 300-800 watt supplies. 12 volts at 7 amps will do minor things. 12 volts at 50 amps will do a bit more....

Having bench top power supplies is a godsend; I have a pair of them myself and can feed all three voltages to a board. Oddly enough I am getting a board with blown FETs on it, I'm debating checking the 1 volt rail, clearing the failures, and trying to power it off the danger board's 1 volt supply. A double-headed jalapeno. :-)

It keeps my mind working.

C