KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

[triplefour]

i got this midi keyboard for 5$ untested, and of course, it doesnt work. doesnt do anything when you give it usb power. i took it apart and near the usb connector i saw that a couple of the SMD components looked charred. i scratched with my fingernail and one of them came loose. they are too small and burnt to tell what they were supposed to be, and of course i cant find any service manual for this device, let alone the individual board inside.
it is marked KLM-3022-D and i can't seem to find a replacement. it seems like it could be an easy fix if i knew what smd components to buy and solder back in place. can anyone help me? are there standard components like this usually found around USB power inputs? they are labeled C2 and L1 .. i assume C2 is some kind of SMD capacitor, but what is L1 ?
this keyboard is actually pretty slick and is not cheap to buy new:
http://www.ebay.com/itm/KORG-USB-MID...UAAOSwYHxWF93t

any help will be greatly appreciated. thanks!

[stj]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

c2 is a capacitor, if it's not shorted then it's o.k.
l1 is an inductor - you can probaby get away with a jumper.

now here is the problem.
the only way the inductor goes up is if something is shorted.

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

So should I try to find the short first? Whats the general method for finding shorts?

[stj]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

first, use a meter to check the 5v and ground pins on the usb connector.
check the ground goes to ground,
and see if the 5v goes to that inductor.
if it does, see if both go to that cap.

i suspect the cap is across the power, and the inductor is inline with the 5v
but i'm interested if the cap is on the connector side of the inductor or the board side.

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

ok i used my meter on diode mode and listened for the beep to look for shorts but i couldnt find any. there are 3 usb connectors on this board (2 of them are outputs, like a usb hub thing, im guessing) and the one square on is for input. each has 4 pins. on each connector, one of the pins has continuity to ground and the other 3 do not. the inductor and cap circuit is repeated for the other 2 connectors and studying those, i was able to figure out to jumper the pad that would have went to L1 properly to the + side of the cap. it doesnt look pretty... but i guess im ready to plug in a usb and measure voltages?

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

hey what do you know, i plugged it in, and windows made the noise, and started trying to find the drivers on windows update...and it found em now to put this whole thing back together and see if it plays!

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

awesome. everything seems to work fine now. thanks stj!

[Khron]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

I wouldn't be entirely shocked if C2 had failed shorted - it wouldn't be the first time i've seen ceramics short. That's how i've revived several laptops in the past.

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

i checked c2, it was not shorted. just had to jumper across L1 and all is good

[stj]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

maybe it got taken out by something plugged into one of the other usb ports.

i'v seen people do some really stupid shit with usb.
one guy blew the ports on a ps3 trying to charge his phone from one!!!

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

shouldnt it normally be ok to charge ur phone via the ps3?

[stj]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

no, the ports are only intended for the controllers or memory-sticks.
they arent intended to supply 500ma-2A that a phone may try to pull

[triplefour]

Re: KORG USB MIDI keyboard microKEY-37 has 2 fried SMD components near USB connector

oh wow good to know!