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USB, Bluetooth and Isight not working

lasagna

macrumors newbie
Original poster
Oct 21, 2008
9
1
USB, Bluetooth and Isight not working

Hi everyone. For a while I have this iMac (Mid 2011 EMC 2428) and only one USB port works on it. For now, I bought a powered USB hub to continue using it, but I would like to try and fix this issue. So, all the other USB ports aren’t working, neither are the bluetooth and iSight camera.
From what I understand, these other parts are internally connected to USB, so I guess it's a widespread issue.
Anyway, the other day I decided to open it up to install an SSD and since I was going thru that trouble I decided to remove the MLB and try to find out if I could also repair the USB issue, by cleaning it or something.
I couldn’t figure anything out. I did clean it a bit with isopropyl alcohol, but nothing changed. The machine is working fine, and faster with the SSD. But I would like to sell it at some point, and not having all USB, bluetooth and iSight working is kinda of a bummer.
I did research a lot online but couldn’t find anything related to this hardware issue.
Please understand I tried all the other solution like resetting SMC, reinstalling OS, etc etc… These devices don’t even show up on Hardware info listing. I even tried installing Windows to see if it would show up there.
Any ideas?
 

USB3foriMac

macrumors regular
Apr 15, 2020
165
64
Singapore
If you have a USB tester, use that to check whether you have the 5V. If you have no USB tester, use a multimeter. If you don't have that either, you won't be able to diagnose further anyway.
If you do, search for K62 MLB 820-2828. This is the 27" schematic. You can then narrow down to the FETs that switch on the 5V power, or maybe one of the ports has a short (ceramic capacitor), putting the power near the limit.
If it's not a power (voltage) issue but a comms issue, you will have a problem, as all ports go to a single chip U1800, the Intel Cougar Point (series 6 chipset). But I doubt it. It's more likely it has do do with a small component.
The current limiter chips are all close to the USB ports. They are tiny, you need a good microscope. I use a digital microscope with a screen.
What could also have happened is that at some point, you ripped a component off the board while mounting. Not sure you observed the issue after an assembly or gradually?
Sometimes, a PRAM reset also helps, just try again if you have already.
 

lasagna

macrumors newbie
Original poster
Oct 21, 2008
9
1
Thanks for the tip. Mine is the 21" inch thou. Do you know what I should search for the schematic?

Thanks again!
 

lasagna

macrumors newbie
Original poster
Oct 21, 2008
9
1
Hello again. So, following your suggestions here are my results:

- I used a multimeter to test the USB ports. All of them are giving me 5 volts. I also have a mouse that lights up when plugged in, and it had lights on on all of them.
- So, after I tested the voltage, I checked and BAM, iSight is back. Also the SD card reader and IR. But I think the last two were already there.
- On system profiler, under USB, I see TWO "ports". One with the iSight camera and hub, the other with SD Card reader, IR and Hub.
- The mouse now works on the first two ports, the same that I can see on the System Profiler. But Bluetooth is not back on.
- I unplugged the BT card and put back on, but no success.
- Now, I believe that if all ports were working, under System Profiler I should see 4 USB Bus in there, right?

The image below is just an example, it's not from my iMac. But it's like I see two USB Bus, one with the IR the other with iSight, and that's all. But I should see 4 Buses in there...

1594332140630.png


Long forward to your help! :)
 

USB3foriMac

macrumors regular
Apr 15, 2020
165
64
Singapore
The mid 2011 21.5in is K60 820-3126-A but they are quite similar.
Screenshot_20200710_080949_com.realvnc.viewer.android~01.jpg

So camera is working and all ports of hub1? Hub2 might have a component defect.
Try a few more times to do SMC and PRAM reset, it wouldn't hurt. I had some stubborn ports, too, which could be revived by that.
If it is obvious that something is wrong with Hub2, check the components around it for defects. Let us know when you get to that, I can point out parts to check.

This is how the device tree looks like:
Screen Shot 2020-07-10 at 8.57.31 AM.png

Note: "Composite device" is a combo keyboard/mouse receiver.

Maybe you can post yours for us to see?
 
Last edited:
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PaulD-UK

macrumors regular
Oct 23, 2009
131
10
Thanks for that.
It explains why my 2011 21.5" iMac hasn't had USB Hub1 working every since I bought it 'open box' 'all faults' for less than half price in 2012.
Everything else has worked fine since then, and it passes the Apple Hardware Test.
The USB Device Tree shows the hub, but not the ext ports or the SD card (and I presume the IR). But the ext ports do get power - only the data lines seem faulty, and I've got a Thunderbolt 1 hub with USB 3, so I've learned to live with the fault ;-)
 
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