Audio interface died, emitting smoke.

[Tonitz]

Wires in a transformer are often coated with varnish or other substances and if heated enough this substance will melt and leak. I have been working with electronics since high school and I am 50 so figure out the length of time.

Yeah another friend told me basically the same thing. He said "The goo is the laquer from the windings in the transformer. It got hot enough to make it liquid again." He's about your age and has been a recording engineer all his life and he also repairs most of his own gear. So I believe this to be true.

Tonitz: That capacitor blew rather spectacularly. The brown goo you see everywhere is the electrolytic gel from inside the capacitor. You're going to want to clean that up with isopropyl alcohol (90% or 99%) and cotton swabs.


Firewire supplies 500mA of 12VDC power, by the way.

I've given it a pretty thorough cleaning. I noticed there was a big difference between the brown goo oozing directly from the transformer and the brown fiber-like stuff from the blown capacitor (see pic below). The fragments of the blown capacitor cleaned up rather easily, and it looks to me like that resistor you mentioned may not be blown after all, and it was just collateral damage left behind from the capacitor in the original pic that made it to appear shot. The brown goo from the transformer wouldn't budge.



Anyway, I plan on replacing the capacitor. I've just got a few issues. When I first took the unit apart I noticed the blown capacitor right away. I lifted off the cap not thinking to check the polarity (there is a negative symbol on one side of the cap). Now I'm not sure which way to install it. Presonus doesn't make available the electrical flow of the unit so is there any other way to figure this out?

Also the issue I keep coming back to is the transformer. If I'm powering it with DC, and the transformer's sole purpose is to convert AC to DC, then why is it getting so hot to the point of melting itself? Shouldn't electrical signal be bypassing the part completely? Given it's close proximity to the blown capacitor, I worry that by simply replacing the capacitor I could run into the same problem in the near future.

[drzinc]

Firewire supplies 500mA of 12VDC power, by the way.

http://support.apple.com/kb/HT2952

Power
Input voltage range: 8 to 33 V
Input power: approximately 0.3 W
Output voltage range: 12 V to 30 V (varies by product)
Output power: minimum of 7 W per port

[djpenguin]

I would think that any parts that were damaged or destroyed would need to be replaced before the sound card will work properly again.

Transformers don't convert AC to DC. They use inductance to convert voltage by stepping it up/down. The number of copper wire windings on each side determines the conversion factor. That little three-legged jim-jam directly above the transformer looks like a voltage regulator, so it's possible that the internals of the sound card use a voltage other than 12V, and the transformer/regulator combo supplies that.

*EDIT* I just looked up the spec sheet for the AMD CMOS flash memory boot chip, and it has an input voltage range of 2.7-3.6VDC. The transformer is definitely necessary for normal operation.

I have the same soundcard sitting in a box downstairs. I can open it up and determine which direction that capacitor should be installed. That's probably the best thing to do short of having the schematics to refer to.

[djpenguin]

The capacitor should be aligned the same as it's neighbor above and to the right of it in your pic, with the negative side oriented towards the top of the picture

http://support.apple.com/kb/HT2952

That's the design spec from the mid-eighties. As implemented in computers and old iPod power supplies, IEEE1394a ports deliver a maximum of 500mA@12VDC. That's what the IEEE1394a ports on this audio interface will be expecting to see.

[drzinc]

The capacitor should be aligned the same as it's neighbor above and to the right of it in your pic, with the negative side oriented towards the top of the picture




That's the design spec from the mid-eighties. As implemented in computers and old iPod power supplies, IEEE1394a ports deliver a maximum of 500mA@12VDC. That's what the IEEE1394a ports on this audio interface will be expecting to see.

I understand that, but if a component fails in a device the full voltage/amperage may flood into the device causing more damage.

[djpenguin]

I understand that, but if a component fails in a device the full voltage/amperage may flood into the device causing more damage.

You are correct, but unless something went wrong with the voltage supply (computer) end of this particular setup, the 1394 controller in the computer should not be allowing more than 500mA@12VDC to be drawn. I'd have to do some research to be sure, but I think the max voltage and current values for 1394 are typically seen only in repeater/extender type devices.

[Tonitz]

The capacitor should be aligned the same as it's neighbor above and to the right of it in your pic, with the negative side oriented towards the top of the picture.

Awesome. What are the odds that you just had one laying around. Thanks for taking the time to look!

[djlotus]

Wires in a transformer are often coated with varnish or other substances and if heated enough this substance will melt and leak. I have been working with electronics since high school and I am 50 so figure out the length of time.

This. Transformers are usually coated and most have an electrolyte between the copper wire and the "iron core", which is actually a magnet and shaped like a square. It would appear your unit took a surge and blew up. The surge would cause over current through through the primary leads on the transformer which would in turn send over current out of the secondary. If the board is not properly protected, which it appears it is not, the over current will blow all kinds of components starting with smallest resistance. You def have a blown cap there and most likely that resistor is shot also. If you are to fix yourself you are looking at replacing the transformer, cap, resistor, most likely a diode or two, and possibly the little guy to the top left of the blown cap.