Hello fellow Electronic Adventurers,
I am new to the forum, hope to get some great advice and some possibly hard to find information.
I am fixing or at least trying to repair a customer's M-Audio M-Track Eight Audio Interface USB who accidentally ripped the USB connector right off of board while traveling, having forgotten to unplug it. Unfortunately, he tried to fix it himself rather clumsily with a huge iron or something, regardless, he cooked the two capacitors flanking the 310 Ohm resistor.
I've searched the internet for a BOM or any information on the microfarad value of the capacitors, so I can order a replacement, but no luck. I will also have to do some trace repair on the other side of the board.
I originally thought it would be a straightforward repair, but when I checked the value with my tester the caps showed open, when I desoldered the USB the caps just disintegrated on me with the heat I had to use, They were already cooked them real good. The resistors value is obvious, and I may be able to guess the cap's value, but I'd rather see a BOM or at least get someone to give me some more expert advice on how much the capacitance would be on a USB output.
Does anyone have a link to a BOM or know what value is common for capacitors used for the USB in this case? I'm an experienced micro-solderer, but not an electrical engineer that can figure this theoretical stuff out, it would give me a headache Lol, I already have enough headache inducing crap in my life, hats off to the engineers, I'm not built for that level.
Any help, or pointing me in the right direction, would be greatly appreciated!
Cheers, from Ottawa, Canada,
Your friend and mine,
EnzoSupremo
I am new to the forum, hope to get some great advice and some possibly hard to find information.
I am fixing or at least trying to repair a customer's M-Audio M-Track Eight Audio Interface USB who accidentally ripped the USB connector right off of board while traveling, having forgotten to unplug it. Unfortunately, he tried to fix it himself rather clumsily with a huge iron or something, regardless, he cooked the two capacitors flanking the 310 Ohm resistor.
I've searched the internet for a BOM or any information on the microfarad value of the capacitors, so I can order a replacement, but no luck. I will also have to do some trace repair on the other side of the board.
I originally thought it would be a straightforward repair, but when I checked the value with my tester the caps showed open, when I desoldered the USB the caps just disintegrated on me with the heat I had to use, They were already cooked them real good. The resistors value is obvious, and I may be able to guess the cap's value, but I'd rather see a BOM or at least get someone to give me some more expert advice on how much the capacitance would be on a USB output.
Does anyone have a link to a BOM or know what value is common for capacitors used for the USB in this case? I'm an experienced micro-solderer, but not an electrical engineer that can figure this theoretical stuff out, it would give me a headache Lol, I already have enough headache inducing crap in my life, hats off to the engineers, I'm not built for that level.
Any help, or pointing me in the right direction, would be greatly appreciated!
Cheers, from Ottawa, Canada,
Your friend and mine,
EnzoSupremo
They look like ceramic caps, they normally take a lot of heat as they are, well, ceramic... Mechanically they are brittle though.
A tester isn't going to understand a capacitor shorted out with small value resistor, they were possibly fine. Seems to be RF coupling between USB ground and circuit ground, values for that might only be a few nF. I'd go for 10nF or 100nF sort of value and hope - they may not be needed for correct operation, but protect against ESD when a lead is plugged in.
From that photo it needs the flux cleaned off and reworking carefully with new flux and a keen eye for damage to the traces particularly where they join the pads.
A tester isn't going to understand a capacitor shorted out with small value resistor, they were possibly fine. Seems to be RF coupling between USB ground and circuit ground, values for that might only be a few nF. I'd go for 10nF or 100nF sort of value and hope - they may not be needed for correct operation, but protect against ESD when a lead is plugged in.
From that photo it needs the flux cleaned off and reworking carefully with new flux and a keen eye for damage to the traces particularly where they join the pads.
The caps did not survive removal, I used two soldering irons to quickly remove them, but they were already delaminated. I've done rework professionally for 20 years, once components are overheated there is no salvaging them. The other side of the board is a mess. I'll send a pic shortly, I'll have to do a trace repair.
The crucial thing was getting some values for the caps and that resistor.
Thanks both of you for such a speedy reply and valuable information. I'm going to see if I have those in stock, and I'll post an update on the outcome.
Great forum!
The crucial thing was getting some values for the caps and that resistor.
Thanks both of you for such a speedy reply and valuable information. I'm going to see if I have those in stock, and I'll post an update on the outcome.
Great forum!
Check with the multimeter.... if I'm correct (see below). Observe the USB socket pins, check the pinouts on the net & trace them on the PCB to confirm.
C96 and C97 are non-critical... they can be 0.01uF. R174 is important (even though it's a 1Mohm)... for the "hand-shake" IF the USB (source) ground (USB cable shield) is not at the same potential as the USB socket shell.
...SP9 is a USB Vbus (+5V DC) coming from the source.
C95 is a local decoupling cap for the D40 IC V+ rail.
C384... is for something else... not related to this USB input circuitry
C96 and C97 are non-critical... they can be 0.01uF. R174 is important (even though it's a 1Mohm)... for the "hand-shake" IF the USB (source) ground (USB cable shield) is not at the same potential as the USB socket shell.
...SP9 is a USB Vbus (+5V DC) coming from the source.
C95 is a local decoupling cap for the D40 IC V+ rail.
C384... is for something else... not related to this USB input circuitry
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Oh. So the caps connect the USB ground to the audio ground. Fun, fun... Their purpose in life is to connect the audio ground and the USB ground at RF. This could have been done to meet EMC or ESD specs, but they're likely not critical for operation otherwise.
I'd start at 100 nF. Hook the device up to a PC powered from a grounded mains outlet. Then measure to see if you get much hum/hiss/noise. If you don't button it up. If you do reduce the capacitors. I'd probably use 1 nF as the lower limit.
You could also ask M-Audio. They might respond or they might not. Either way it only costs an email.
I'm amazed that the owner managed to cook the caps. Did they use a heat gun or something? If so, there could be more damage.
Tom
I'd start at 100 nF. Hook the device up to a PC powered from a grounded mains outlet. Then measure to see if you get much hum/hiss/noise. If you don't button it up. If you do reduce the capacitors. I'd probably use 1 nF as the lower limit.
You could also ask M-Audio. They might respond or they might not. Either way it only costs an email.
I'm amazed that the owner managed to cook the caps. Did they use a heat gun or something? If so, there could be more damage.
Tom
Looking at the layout D40 is quite likely USBLC6 (or similar) used for ESD protection.
Oh interesting. In that case I'd probably worry even less about the exact value.
Tom
Interesting indeed. Ignorance is bliss. No need to worry about plops/clicks every now and then...
Yeah... the one (Zener) going to Vbus + is the one that confused me. But you are right...
....something like this:
That looks like remnants of a small common mode choke. E.g. https://product.tdk.com/system/file.../catalog/cmf_commercial_signal_acm2012_en.pdf
Cleaning the board should reveal more. If there are 4 pads then it is a common mode choke.
