Repair Usb Audio interface Focustrite 2i4

[magic]

USB 1.x/2.0 devices should tolerate shorts between any two pins indefinitely.
That being said, maybe that's too much to expect from audio gear

Post a pic of the blown parts and their neighborhood.

[Countrypicker]

Hey Magic,  thanks for the fast reply. I'm at work right now but I will take pics when I get home (Based in Scotland). I just figured out what those codes are (SMD Codes). I'll use a big magnifier and see if I can decipher the code. I used to be an electronics tech way back in my Air Force days but they didn't use surface mount components in those days. (Old Timer)  . Regarding shorting out pins, I wonder what 5 volts down the input pins of the USB Controller chip would do. It already blew off the little inductors at the input. Also blew off chip U38 and R51. I have ordered a USB3343 chip just in case.

[Countrypicker]

Pics attached. I found U38 detached inside the casing. It is marked SDERCG. A previous comment says this is NCP303LSN09 but I think that's wrong. I looked up the SDM code and it says LM3670MF-3.3. That's a DC Voltage drop down device 5 Volts to 3.3. Makes sense as the Processor, USB Controller and the Cirrus Logic DAC all use 3.3 volts. U39 is marked Z074. That appears to be  a Fairchild NC7WZ07P6X Dual Buffer. The middle 2 pins appear to be unconnected so that ties in with the Chip schematic. C137 should be 1 uF capacitor according to USN 3343 Data Sheet.

[Zucca]

I found U38 detached inside the casing

Strange, those do not came off so easy, do not spit on my face but maybe is overheating and desoldering itself?
It's a mistery.

[Countrypicker]

R51, L5, C137, C139 all missing. C137 should be 1 uF according to the USB3343 Data Sheet. Not sure about C139 - maybe it was never there. This was caused by someone trying to replace the USB connector. He shorted the Data pins to the +5V line with a solder splash. 

[Zucca]

Another moron before us, very common story unfortunately.

[magic]

Regarding shorting out pins, I wonder what 5 volts down the input pins of the USB Controller chip would do.

Nothing interesting in principle, though I haven't had an opportunity to test it in real life yet

Universal Serial Bus Specification Revision 2.0, 7.1.1 USB Driver Characteristics, page 124

A USB transceiver is required to withstand a continuous short circuit of D+ and/or D- to VBUS, GND, other data
line, or the cable shield at the connector, for a minimum of 24 hours without degradation.  It is recommended
that transceivers be designed so as to withstand such short circuits indefinitely.  The device must not be damaged
under this short circuit condition when transmitting 50% of the time and receiving 50% of the time (in all
supported speeds).  The transmit phase consists of a symmetrical signal that toggles between drive high and
drive low.  This requirement must be met for max value of VBUS (5.25 V).

I will tell you what happened: the previous owner knocked these components off the board while trying to replace the USB connector. Or maybe desoldered them and couldn't put them back. Or lost them, or broke them during desoldering.

Either that or he managed to apply mains voltage to the USB input. But there are no smoke stains.

As for the data lines, I bet they go straight through L5 to U4. L5 was a common mode choke to suppress EMI, the device will work without it (replace with two straight wires). Then you may look for a proper replacement, but I am not familiar with that stuff.

The only serious problem is the mayhem around U38. You need to identify it. It doesn't look like a switching regulator, because there is no coil in the vicinity.

edit
Trace how things are connected around U38 and U39 and post a schematic.

That guy from Poland has 47kΩ at R51. Both he and the Brazilian have nothing at C139.

Is your U38 visibly broken or only disconnected from the board?

[Countrypicker]

I see from other pictures on the web that C139 is empty so can rule that out. Yes, the data lines do go through L5 to pins 13 and 14 on the USB3343. I have a replacement choke for L5. I am fairly sure I have correctly identified U38. (LM3670MF-3.3) The part I found rattling around inside the device has no connections to solder it back in. Just a black chip with no legs and marked SDERCG.

[magic]

I wonder if this thread might be about the same one unit which is being broken a little bit more by each new owner and then sold on eBay to the next one

U38 is not LM3670-3.3, don't try it. Firstly, the marking doesn't match (SDER vs SDEB). Secondly, there is no inductor nearby so U38 wasn't an SMPS chip.

Too bad that the original part is nonfunctional. NCP303LSN09 is a reasonable match (the datasheet says: marking SDE). You may order a new one and see if it looks the same (same number of letters, font style and size).

Try to figure out how the circuit is wired and whether NCP303LSN09 makes sense in this place in terms of pinout and function.

[Countrypicker]

Thanks Magic. NCP303LSN09T1 ordered.

[stuartmp]

Hi Guy's

Just wondering if someone can tell me the value of R40 on a Scarlett 2i4 as I somehow blow it up last night.

See attached image for the location

I'm assuming that once I know the value I can just replace it the a regular 1/4 watt resistor of the same size.

Thanks

[magic]

A more interesting question: what it is doing there and why did it blow up out of a sudden?

[stuartmp]

I was just switching over a whole heap of leads over not paying attention. Do you know the value of R40?

The device seams to be working fine otherwise. So I don't really know what it does. I traced on end to the phantom power switch and the other end to the IC near by.

[magic]

I don't own this device so can't help.

Se what IC it goes to and find the datasheet. Chances are that this circuit just follows the chip manufacturer's reference design.

[diegooo1972]

I had a short between 0v and 5v. I finally isolated with the best analyzing instrument ever. The thumb. The problem riside in a componet marked as IAFEF. My best guess after few serach is that is compatible with IAFEE which seems to be a MP2159GJ-Z (wrong. it's not). But I can't find any infromation about IAFEF. Someone can point me to information about this component ? I'm quite inexperienced.
Edit: Just found another thread here where it seems that also IAFEH is the Mp2159GJ-z. It seems to me that IAFEF, IAFEE, IAFEH are all the same. I'm going to buy them and try to cheange the faulty component anyway. Just love a confirmation.

update 1: the Mp2159GJ-z is not equivalent to IAFEF.

[jpm1680]

can someone help me whit some reference to check that voltages.. please.. no schematic on internet

I know this is an old thread, but I wanted to get Braian some resolution on this.

I just opened up my neighbor's 2i4, and it had the same issue as yours. L12 getting super hot. Unfortunately my finger is not sensitive enough to detect the other hotspots on the board, so I borrowed a thermal camera from someone.

The right spots are the inductors, as you already know about.


I zoomed in on the left hotspot, and it's one of the HC4066AG multi-switch ICs.


Without power, the other HC4066AG ICs had nominal resistance from the inputs (pins 1, 4, 8, and 11) and outputs (pins 2, 3, 9, 10)  to GND (pin 7). This one had 2.4Ω on A and B inputs and outputs. While I expected anything connected to the shorted inductor to have minimal resistance to GND, the fact that both the input and the output were shorted made me suspicious. I removed the component, and sure enough, the pins measured 2.4Ω to GND without being mounted. And now the 2i4 is working as an output device. I've ordered a replacement part, and hopefully that will restore full functionality.

[chanobass]

Great! Thank you very much! I'm missing the L5, and the one in light blue, I think it's the C137. Can you help me with the C137 please. Thank you very much!!