[XCSSA] Blowing Fuses and Unsure Why

[X-otic Computer Systems of San Antonio]

Man I want to try that out :) Seems like a really neat idea!  
Fortunately, I was able to stop blowing fuses. I ended up changing a  
few things - I went with panel mount fuse holders (the glass tube type  
instead of the picos) as these were easy, cheap, and plentiful. I  
cheated a bit here and put the fuses after the xformer (instead of  
after the rectifier). I could risk doing more damage this way but I'm  
going to try and figure out a better solution when I start perfecting  
it. I also went down to the single rectifier solution I mentioned  
earlier and removed a few caps that may not have been needed (that,  
and I ran out of extra caps :P)

Everything is working now, although I have yet to put a larger load on  
it other than the 2 LEDs. Here's some pics:

https://www.moocowproductions.org/photodawg/album.php?albumID=27

(Yes I know it's messy and my protoboarding skills have much to be  
desired :P The eventual goal is to get a printed board of this thing).

There's a discussion on the MidiBox forums (a rather good one I might  
add) about what implications this design, and other designs, have and  
might be a good read if people are interested:

http://www.midibox.org/forum/index.php/topic,12695.0.html

I hope to test the waters with a power source that draws more load.  
Actually, I guess I could actually use a light-bulb for that too!  
Hmm...well either way, I'm going to work on soldering parts to the  
MB-6582 mainboard. There's a lot so I don't know how far I will get,  
so I may try to test it with my existing SID synth (the one I showed  
everyone a few months back).

Oh one more thing - those not wanting to look at the forum post might  
still be interested in one of the links off it:

http://www.falstad.com/circuit/

Dunno if people already knew about it, but it's fun to play with this  
stuff (the interface has a bit to be desired, but does work).

Will keep everyone posted!

Tim



On Jan 11, 2009, at 12:46 AM, X-otic Computer Systems of San Antonio  
wrote:

> On Friday 09 January 2009 11:23:16 am X-otic Computer Systems of San  
> Antonio
> wrote:
> [...]
>> I think I get what you're saying, but that's for if the fuse on the
>> left of my xformer blows right? Can I use this setup if one of my
>> fuses blows to the right of the xformer? The only fuse that's blowing
>> is on the 9V rail - the 5V works just fine before and after the fuse
>> blows on the other side.
>
> Depends on how much current it's drawing.  You can decrease the  
> wattage of the
> bulb until it stops blowing the low voltage fuses... (300W, 150,  
> 100, 60, 40,
> etc) then you can work safely.
>
> But I would disconnect caps, regulators and components until you  
> either stop
> blowing fuses or the light bulb goes out.
>
> Another, safer way you could also do this passively, with the power  
> shut off
> and disconnecting the transformer by just watching the resistance of  
> the 9V
> circuit with a DMM Ohm meter (after you disconnect the transformer).
>
>
>> Now, if I understand you correctly, I can hook this up so that the
>> bulb lights up iff there is a short?
>
> Yes.  Or more specifically.. the closer you get to drawing 3Amps on  
> the AC
> side (with a 300W bulb), the brighter the bulb gets (the ampergace  
> will not
> be GREATER than 3Amps because the bulb limits the AC current to  
> three amps
> (pre transformer amps) because the bulb's wattage (300) will limit  
> it to
> 300W/110v=2.7A.  If you want to limit it to around 0.9A, then switch  
> to a
> 100W bulb.  Get it?
>
>
>> I'm a little fuzzy on that so I
>> don't suppose you have a picture? I actually have extra light bulbs,
>> so this might work out well!
>
> meh.. I googled for some.. but it's not an off the shelf lab/bench  
> device.
> Just old timers who do a lot of bench work build them.  Let me  
> render an
> ascii schematic for you:
>               _ bulb  switch
> -AC-hot-------/ \------o/ o ---o AC hot
> -------------------------------o AC gnd
> -------------------------------o AC neutral
>
> (switch to mono space fonts to view that)
>
> In your case.. I would try the passive DMM/short detection method  
> first (have
> to disconnect the xformer from the board).  Then if that doesn't  
> help yo
> ufind it.. do the light bulb thing.
>
> Tweeks
> _______________________________________________
> XCSSA mailing list
> XCSSA at xcssa.org
> http://xcssa.org/mailman/listinfo/xcssa
>