FWIW,  I was thinking that I wouldn't be sleep properly for a week or so until 
I can order/receive a new low-ESR cap (330uf), so I dug up a 1000uf 50V 
generic-ESR electrolytic and soldered it in place.  The PS works beautifully 
now.  And the cap is oriented (polarity) the same as the blown cap.  I will 
replace with the correct cap when I get it though.

I still need to see what sort of ripple I get on it (my scope is not here 
currently), heatsink the chips, and test will all outputs under 
significant/max load, but at this point all looks good so far.

BTW, on the subject of minimum loads, the datasheet for National's LM2678 does 
not state anything about minimum load, but I noticed that the output voltage 
was off (~4.2V) without a load, but came back within spec with a 1k load 
resistor in place.  The other outputs have the proper voltages w/o a load.

Much thanks,
-Neil.



On Thursday 25 November 2004 08:36 am, the madscientist scribbled:
> just be very careful with the grounding, it is very hard to get good
> scope traces in a switching power supply, especially with multiple
> switchers running because there is a lot of noise.  most of the switcher
> data sheets/app notes i've read go to great lengths to explain this and
> show what is necessary to get a meaningful scope trace in a single
> switcher, with 3 switchers running it's worse.  did you design the
> circuit board?  i know layout is somewhat critical with switchers.
>
> PicDude wrote:
> ------
>
> > I'll get a scope on it the next time to see if anything unexpected is
> > happening.
>
> --------


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