[zlobby]

My presonus firebox was functioning normally up until a few days ago.  I was going to listen to some music, and noticed that the LED in the front was off, so I assumed I must have knocked the firewire cable out.  This was not the case, everything was plugged in fine.  So i unplugged and plugged it back in.  The led flickered a little bit, and then i heard a loud pop, and then death of the unit.  It smelled of smoke too.  Presonus wants to charge me $75 to fix it.  I am pretty handy, and was wondering if anyone here would be able to help me figure out what I might have blown, and not spend $75 to replace this damn thing.  

 

[xslimmiejimmiex]

I have a Firebox too. The only way to know is for you to unscrew the chassis and open it up to see the damage...
 
Perhaps you weren't using the 12V adapter (its for more stability). However, I hear the adapters can be faulty sometimes, too..
 
Also, what operating system are you using?
Desktop or a laptop?
 
Could've been:
-failed capacitor
-burnt resistor
-burnt switching regulator
 
If you want to save money, buy the parts...
If you want to spend more; E-MU 0404 or especially the E-MU 1616

 

[zlobby]

I wasn't using the AC cord, i always just powered it with the firewire cable.  I use a win 7 desktop.  I am considering buying and emu regardless because it has a better DAC, because my interface serves dual function (recording and dac).  But i would at least like to fix this and resell it to recoup some costs.  
 
EDIT:
 
Ok so i opened her up and I found one cap that looks physically damaged.  Also at about 4 o'clock to the cap there is a diode(i think) that has some browning around the solder.  Some of the 1/4" outputs look as if they have been burned and have that rainbowing associated with heating metal.  Aside from the cap thats obviously toast, what are the chances that this took out other parts of the board?  In terms of electrical shock, how much threat does this unit pose at the moment?
 
 
 
 

 
 

 

 

 

 

[FallenAngel]

Open it up, take photos, post them, look for damage.

 

[zlobby]

I cant read what it says on the diode that appears fried.  If anyone that has a firebox could tell me what the numbers/letters on that, it would be greatly appreciated.  Presonus wont give me a schematic 

 

[FallenAngel]

That's a capacitor, not diode.  Just cut it off and look for what markings it has on there (or see if there is an identical sized one beside it).

 

[zlobby]

Quote:

That's a capacitor, not diode.  Just cut it off and look for what markings it has on there (or see if there is an identical sized one beside it).

Im aware that the cylinder is a cap (33uF 63v), but the rectangular thing adjacent (4 o'clock) to the cap looks fried too.  Thats a SMD right?

 

[beerguy0]

Quote:

Im aware that the cylinder is a cap (33uF 63v), but the rectangular thing adjacent (4 o'clock) to the cap looks fried too.  Thats a SMD right?

Could be a resistor. Can you get a little closer shot of that part? (Or better focus?) It's hard to tell what it is in the picture, but it looks more like a resistor to me.
 

 

[zlobby]

 
here is the part in question with better focus.  I removed the capacitor already. 

 

[FallenAngel]

Any way to clean the part off a little, there should be some markings on it, kind of looks like a chip resistor.

 

[zlobby]

It is in fact a resistor.  I wasnt able to see anything after cleaning it off a bit.  After looking around some, I came across this forum, in which a guy had almost the same problem I have.
 
http://www.prodigy-pro.com/diy/index.php?topic=38350.0
 
his image of what failed is below
 

 
He fixed his problem, unfortunately he didnt post the values for the resistor.  It turns out the cap in the bottom left corner of mine failed too, just didnt notice because it didnt explode.  How do I test to see if my switching regulator is fried like his? 

 

[Poolboy]

Hi Zlobby,
 
I appear to have the exact same problem and I have registered here purely because of it.
 
I`m a complete noob at electronics so I doubt I could fix the problem myself, particularly soldering in such tiny components. If it helps the Capacitor in question in my unit has the number uF63 v 33.
 
What is the technical term for the tiny square part?

 

[tangent]

Quote:

It is in fact a resistor.  I wasnt able to see anything after cleaning it off a bit.  After looking around some, I came across this forum, in which a guy had almost the same problem I have.
 
http://www.prodigy-pro.com/diy/index.php?topic=38350.0
 
his image of what failed is below
 

 
He fixed his problem, unfortunately he didnt post the values for the resistor.  It turns out the cap in the bottom left corner of mine failed too, just didnt notice because it didnt explode.

 
Clockwise, from lower-left, the parts are:
 

1. Electrolytic capacitor, 470 μF 10 V
2. 0805 chip resistor, 10 kΩ
3. Electrolytic capacitor, 33 μF 63 V
4. LM2586S-ADJ adjustable-voltage switching regulator

 
There's no way of telling what type of resistor they used just by looking at it.  My guess is 1% 1/8 W thick film, but that's only based on popularity of that resistor type, not on any knowledge of the circuit.  The only circuit knowledge I'll admit to is that it looks like it's just being used as a current limiter in series with the other SMD parts you can see in that loop, so I'd guess that the resistor type isn't critical.
 
Quote:

How do I test to see if my switching regulator is fried like his? 

 
Replace the known-damaged parts with good ones, turn it on, and see if they explode again.  If they do, replace the LM2586, too.
 
It could be that the cap gave up the ghost first, and its sudden absence caused the event that took out everything else.  If so, the fresh cap will keep everything else alive.
 
It could also be that the regulator died first, and that blew up everything sensitive around it.
 
Quote:

I doubt I could fix the problem myself, particularly soldering in such tiny components.

0805 is indeed quite small.  I'd put that right on the borderline of DIY hobbyist hand-solderability.  I've done it before.  It's not fun, but with the right technique, you don't even need special tools.  See my soldering videos: Tangent Tutorials.

 

[Poolboy]

 
Quote:

0805 is indeed quite small.  I'd put that right on the borderline of DIY hobbyist hand-solderability.  I've done it before.  It's not fun, but with the right technique, you don't even need special tools.  See my soldering videos: Tangent Tutorials.

I could watch your Tutorials until the cows come home but I have little or no soldering experience and there is no way I could solder that tiny resistor in there. I will have to seek out a professional somewhere locally. Thanks for your reply though.
 
I guess this is the reason Presonus christened it the Firebox...

 

[qusp]

pfft, try soldering 0402 and tell me 0805 is small, my home dac/amp has about 400 0805 (this may seem ridiculous, but is a rough estimate of all systems, 4 channel balanced dac, USB, fifo buffer, DSP, clock and all digital inputs, something like 35-40 regulators and all control, monitor systems) and close on 100 0603, but 0402 just aint gonna happen. 0805 really are quite easily done once you have the technique.