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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
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
239
86
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.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Thanks for the tip. Mine is the 21" inch thou. Do you know what I should search for the schematic?

Thanks again!
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
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! :)
 
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USB3foriMac

macrumors regular
Apr 15, 2020
239
86
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?
 
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PaulD-UK

macrumors regular
Oct 23, 2009
137
13
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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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Hi Paul, just saw your response... Thats interesting. I was just playing with mine again, since I wanna make a decision on what to do and close it already.

So here's where I am right now:

- Indeed only one USB port works flawlessly, the one next to the Firewire port.
- The second USB works with the mouse for a few seconds and stops. I had the luck of it coming back to work just to stop again some seconds later.
- The other ports only have power like Paul mentioned above.
- My FaceTime camera appears on the System Profiler and it works intermittently. Lots of flashes, and one time it was not being identified.

Today I tried disconnecting the BT/Airport cable from the motherboard, to see if it could be a short circuit between these cables.

As of now, I think the problem is somewhere in the board and I wouldn't be able to repair myself.

Thoughts???
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Maybe you can post yours for us to see?
Sorry I didn't see this being replied before. Awesome response...

Your diagram explains it all... so what should I check there? im gonna take it apart again and take a look on the board.

So, mine shows two as well, one showing FaceTime, but not Bluetooth, and any device I plug into USB 1 (the one next to the Firewire).

The other one shows IR and Sd Card reader.

1607468284446.jpeg


But you seemed to be able to plug something into that port as well... So I guess two ports connects to Hub 1 (with camera and bluetooth) and the other two with the SD Card reader?
 
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USB3foriMac

macrumors regular
Apr 15, 2020
239
86
Singapore
Look again at the diagram I posted earlier. It seems your Hub2 has problems. However, the camera is not on Hub2, so why would that be affected?! Maybe the power supply line to the entire usb ports. Something might draw too much power and cause the supply to go into current limit.
To troubleshoot, I'd do the following:
Open up the unit, disconnect camera, bluetooth, as card reader and IR board.
Test all ports for result.
If ok, plug in one by one of the internal devices. One at a time. If all work by themselves, start connecting in combinations.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
image.jpg


here we go. After I disconnected everything only the two hubs appears here.

Still none of the other 3 ports are working. I am using a hub on port 1 to connect two keyboards and a mouse.

what I find odd is that the one iMac hub says current available ma 500 but only 2 for current required.
Even thou it has three (low) power devices.

so yeah that didn’t solve.
Oh I also reset the pram like 20
Times.
Time to check the board ?
 
Comment

USB3foriMac

macrumors regular
Apr 15, 2020
239
86
Singapore
Step by step.
We want to figure out whether the hubs are both ok, and whether the internal devices are ok.
Maybe use an external screen, then you can leave your imac screen off and access the devices faster.
Step 1: all disconnected*. Result: this shows hub 1 and hub 2 appearing.
Step 2: Test any of the external ports with the same device (use a mouse for this test). Result: one port works, the others don't (correct?)
Step 3: Connect the internal camera and nothing else*. Result:
Step 4: Connect SD card reader and nothing else* and check SD card operation (hub 1). Result:
Step 5: Connect Bluetooth and nothing else*. Check bluetooth operation (hub 2). Result:
At each step, take the screenshot of the USB device tree. Then we can see what is working and how it is detected.

If you have an externally powered USB hub, you better use that. This will not draw much current from your internal USB source.

If you have a multimeter and understand voltage and current, you could
- check the 5V output of each port.
- use an external 5V supply to power a USB device and only feed the data signals to the iMac ports to check whether the data ports are still working and the issue is caused by the internal 5V supply.
- simulate different loads using resistors (100 Ohm = 50mA, standard 0.25W resistors) to determine the current limit of each port. To simulate higher loads, simply connect multiple 100 Ohm in parallel to the port. If you have n 100_Ohm resistors, the resulting resistance will be 100/n Ohm. Current I = 5 x n / 100 [A]. So if you have 10 resistors in parallel, it is 5 * 10 / 100 = 0.5 A.
Do not use a single 10 Ohm, as this will cause a power dissipation of 2.5W and the resistor will get extremely hot and may burn.


* this refers to internal and external USB devices.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Merry Xmas! :) Best time to run some tests, right?

Okay here are my findings:

  1. Nothing plugged in, both Hubs appear on system profile
  2. By testing the ports with a keyboard, only Port 1 worked.
  3. iSight camera works, but from previous experience its unstable. I tried making a video but it didn't show much this time, but it flicks and also sometimes simply doesn't work. Maybe when there's more devices connected.
  4. SD Card works great, and always have.
  5. BT was the first to disappear and it's the reason I'm investigating this. I wonder if the BT card itself isn't fried.


I also tried an external USB HD (with a power adapter), and it actually worked on Ports 1 (EXTD) and 2 (EXTC).

Port 2 has been a mystery. Sometimes when I test port 1 with a mouse and then I move it to port 2 (EXTC), mouse works for a little bit then dies.

So I am stress testing the HD on this port to make sure it will continually work. And it did work quite well.


So, now I tested my Powered USB Hub and it only works on Port 1, but not on 2. This is strange since the HD worked on Port 2.

The Hub adapter was 5v, so I decided to go nuts and used the 12v power adapter from the HD on it. And it shut down my iMac. I guess it sent too much power to the iMac from the hub.

A few more details:
  1. I found an old bluetooth dongle (I knew I should've kept it for all these years) and it worked on the iMac, so I can connect a keyboard and mouse and trackpad.
  2. Using a simple USB hub on Port 1 (EXTD), I was able to connect a mouse, the BT dongle, a flash drive and my iPhone charger, without the need for external power. Im considering this as a final solution.
    tempImagenEsYUx.png
  3. Port 2 worked for a while, with the same hub, but I can't figure out how to replicate it.
  4. I have all the internal components turned on now. Indeed SD and airport work, but no BT.
  5. I tested the voltage on all ports and I get 5V normally.
    tempImagetVWXmg.png

    Enjoy your holidays and thanks for all the help once again!
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
To sum it up, I believe this is where we are at:

USB__Bluetooth_and_Isight_not_working___MacRumors_Forums.png


EXTD is the one that always works.
EXTC is the one that works sometimes, but it did work with my hard drive with an external power supply.
EXTA and B never works for data.
All ports have 5V, all of them charged my iPhone.
BT is never found.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Now I’m wondering if it’s not a matter of cleaning this board
2C54FA27-E69A-4ED9-98DA-EAA6BAD2F050.jpeg
 
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USB3foriMac

macrumors regular
Apr 15, 2020
239
86
Singapore
EXTD is the one that always works.
EXTC is the one that works sometimes, but it did work with my hard drive with an external power supply.
EXTA and B never works for data.
All ports have 5V, all of them charged my iPhone.
BT is never found.
Well done, and great visualisation.
So I'd say in principle, your voltage is ok, and your hubs are at least partially ok. So there's hope.
What concerns me is the camera, at this goes into the chipset directly, and also has problems.
Bluetooth and SD card reader are powered by 3.3V. So there's another riddle why one works but not the other.

Now I’m wondering if it’s not a matter of cleaning this board
If this is dust, you surely should clean the board. You need to take it out, and use a brush. If I clean PCBs, I normally use alcohol in a spray bottle and brush and spray until the board is clean. Dirt can indeed cause low-ohmic pathways and cause electrical problems.

The Hub adapter was 5v, so I decided to go nuts and used the 12v power adapter from the HD on it. And it shut down my iMac. I guess it sent too much power to the iMac from the hub.
Don't do that. USB is only for 5V, and you can not only damage your hub but also the protection circuit internal to the Mac. For prolonged over voltage, it will burn the chips, so you better not do that.

So best right now is:
- clean the PCB thoroughly, also around the IC pins, and then re-test.
- disconnect the bluetooth PCB (there is a connector), re-test, see what impact that has.
- use a hub on port 1
- you could also try to connect a hub directly to the chipset, there are many USB ports available, but possibly they are not accessible.
- You could try to connect a POWERED hub to the USB pins of the camera connector, as see what happens.
If that works, you can connect all the internal devices to this, at least in terms of data lines. For BT and SD reader, you need a voltage regulator mod, see here: Post on camera, BT, SD card reader
Once you have the POWERED hub working, you can then try to tap 5V from the internal 5V rather than use the external power. However, taking the 5V from the camera connector is quite daring, as the current is limited.

EDIT:
You could also follow this thread Post on camera, BT, SD card reader and connect the camera/SD card reader/Bluetooth to another PC to see whether it is working correctly.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
We keep talking about power here but I thought we were clear that power is not the issue ? (Quick middle of
The night reply)
 
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USB3foriMac

macrumors regular
Apr 15, 2020
239
86
Singapore
I thought we were clear that power is not the issue
You can of course draw any conclusion you like.
I'm not convinced that power issue can be excluded. The driver ICs are powered by 3.3V and 5V supplies. If the voltage is not stable, for example (e.g. a capacitor died), you can have all sorts of behaviour. If you don't have a scope to check the supply ripple, is it correct to exclude it?

Something special about the 4th port (EXT_D, port 3) is that it goes through a multiplexer chip to switch between SMC and USB. The power for the port comes from the same IC that also powers EXT_C (port 2). However, I can't see how this would improve things.

The ports have a protection circuit, consisting of several diodes. It is possible that some of these are shorted, causing a short of one of the data lines. To check that in Power-OFF condition (unplug!), you could use a diode meter and check from the data lines to +5V and 0V. You should be able to measure the diode forward voltage in one direction and no forward voltage in the other, for each data line.
1608997386591.png

A fault would likely cause unstable or no communication. You could use a scope to measure the signal, so that you would be able to observe the differential signal between Data + and Data -.

Some ideas of what else can be done are already in my post #15. I tried to help you narrow down of what the problem could be, but we weren't able to pinpoint whether
- the problem is with hub 1 or hub 2, or even both (both work partial only)
- this is a voltage issue or overcurrent issue (e.g. short circuit of a port) (it appears not to, but we can only confirm the 5V not the operating voltage of the hub/logic ICs which is 3.3V)

The only thing we appear to be able to confirm is that the problem is not specific to a particular USB device.
As that is so, I suggested to use some internal hub to hang the internal devices onto that rather than having them unused.

A plausible explanation is that you had some surge damage that damaged or degraded internal components as well as some of your internal devices. Such surge damage can occur if for example you have an externally powered USB device connected, and you get a surge coming from that external power supply, e.g. when it gets spoilt, or when there is a lightning strike in the area.
If you never had externally power devices connected, it is extremely unlikely that damage would occur.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Thanks again for your time and your patience. Oh boys these things are complex. I thought that since we are getting power from the USB ports, power wouldn't be the issue.

I will see if I can try your other suggestions, as Im not that savvy in electronics, although im trying to learn more :)

But I guess I will just focus on the external hub and move on with my life...
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
I got worse :( I was about to post an ad to sell it (informing all the details about the issue of course), but now its worse. Now it complains about devices using too much power, and will barely work.

Sorry, just wanted to vent here :p
 
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USB3foriMac

macrumors regular
Apr 15, 2020
239
86
Singapore
If you got a soldering iron and you are out of other options (e.g. powered hub onto internal USB ports), then I could advise you which components to take out and which ones to bridge to try to get it working without all the protective components.
There is a risk that this could damage your ports, e.g. if you have an external surge, but before you throw it away, why not?
A first test would be to remove one of the D4600/4610/4620/4630 (port 0/1/2/3). these are tiny 6-pin black pieces. the function is clamping diode: it protects the internal USB data lines from external overvoltages (e.g. from a surge). See picture above showing D4630.
You can simply remove it. If function is restored, it means one/several of the internal protection diodes are shorted.
Note that the camera and bluetooth ports do not have such diodes. So if these 2 ports are also not working, there is a low chance only that removing the diodes would restore function.

A slow death is often associated with electrolytic capacitors. So you could watch out for cylindrical components. If you see bulging, they are spoilt. The affected components could be C3538 + C3544 (near USB Hub1 U3500), C3638 + C3644 (near USB Hub2 U3600), and C4602+C4622 (should be near the USB ports). They could be spoilt even if they are not bulged. C4602+4622 are most likely candidates. They are 330uF 6.3V rated. You could try to replace them, or solder another capacitor in parallel for testing purpose.

Other than that (and the dust you mentioned earlier, have you cleaned that?), I don't really see what could cause this. Wish you luck.
 
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lasagna

macrumors newbie
Original poster
Oct 21, 2008
20
1
Thanks for your time to put this together. Unfortunately I’m very new to electronics so I’m taking it to a repair shop. Fingers crossed.
 
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