[XCSSA] Blowing Fuses and Unsure Why

[X-otic Computer Systems of San Antonio]

The DMM doesn't show any anomalies, but I like the wirewrap as a fuse  
idea ;) I may pick up more fuses from Allied though, as Charles  
suggested. Trouble is I ran out of room on my protoboard for a real  
fuse holder :) I'm going to try and see if Allied has some protoboards  
tomorrow though when I get more fuses. I know the Radio Shack by my  
house has some, but they are too small for something like this (last I  
checked, anyway). I also have at least one more 7805 and 7809 so  
swapping them out is no problem.

I asked this same question on the Midibox forums, too, and they  
suggested an alternative design using a single rectifier that I may  
try as well. Fewer parts means it's easier to troubleshoot if nothing  
else (picture attached). It's based off a bipolar power-supply in a  
way. They also suggested a different capacitor configuration that  
removes more components. So I may try this and see where this gets me  
(fortunately, I bought extra parts assuming all this wouldn't work  
right the first time :)
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Thanks for all the help Charles and Lou & All!




On Jan 9, 2009, at 11:10 AM, X-otic Computer Systems of San Antonio  
wrote:

> Temporary trouble shooting fuse with 30gauge wire wrap wire: should  
> have added a
> caveat, if you're familiar with and have some wire wrap wire.  If  
> not, a single
> strand of copper wire from a stranded AC line cord would work.
>
> This allows a few more seconds than your Pico fuse to blow.  Believe  
> your Pico fuse
> has radial leads, this facilitates insertion of the above mentioned  
> wire into the
> fuse holder.
>
> If the 9V regulator is shorted, and remembering what I said about  
> fingers, you would
> find it warm~hot to the touch, depending on how long it draws current.
>
> Another off chance thought, are you sure your .5A Pico fuse are . 
> 5A ?  .There is
> nothing in your circuit that comes close to drawing .5A/500mA
>
> The circuitry is very simple, full wave bridge and a three terminal  
> regulator, not
> much to go wrong, save a solder splash, incomplete etch of the  
> circuit board, or
> wrong artwork.
>
> A trusty DMM  and magnifying glass is your best friend.
>
> Lou
>
>
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