> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of Peter Todd
>
> My second bright idea (ha!) was to try to reduce the voltage drop by
> using those fancy schottky diodes I noticed in the catalogs... So I
> ordered three 115CNQ015ASL-ND 15V 110A and made them into a diode
> bridge. (they are two diode packages) That worked 
> beautifully, giving me a usable 4.2V line, until after about 30 minutes 
> of running I heard a loud bang. The main AC fuse had blown, though not 
> the 40A DC fuse, and the after some testing the diodes were found to have 
> developed internal shorts. All three seem to have done this at once!
> 
> So, any ideas where I was going wrong? One possible culprit I think is
> how I soldered them, I made up a circuit board and used a heat gun to
> heat the whole packages up and "reflow" the heat-spreader tabs to the
> PCB. All this done without much regard to temperature other than go
> slowly and use as little heat as need be.

Check the specification of those Schottky diodes. Often they can not
withstand high reverse voltage. I think this could well be the
reason of failure for your diodes.

Do you have Varistors before the diode bridge? This might help as well.

Regards,
Xiaofan

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