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PostPosted: Mon Jan 25, 2016 5:12 pm 

Joined: Sun Dec 13, 2015 10:26 pm
Posts: 7
So, I had some interesting issues with wifi and bluetooth over the last few weeks.
I thought I would share the resolution of these issues. Let's start with config:
  • CF-31 Mk2
  • 8Gb Ram, 1TB SSD,
  • Toshiba Bluetooth, Centrino 6205 Wifi, Sierra Wireless 3G+ (Gobi 3000 clone)
  • GPS
  • Runs Windows 10 (very unproblematically)

The original problem
At some point the PC developed an issue where the wifi needed to be reset with the hardware switch every time the PC was resumed from sleep; I use sleep mode a lot so this was incredibly annoying.

As part of trouble shooting I removed the 3G card and BT card, to look for potential conflicts. After some driver uninstall and install, everything started working as before and I no longer had any issues with the wifi... Except Bluetooth. Bluetooth was now gone.

While trouble shooting I replaced almost every single part of the PC, except the motherboard. I replaced 3G board, BT board, PCI-E interface board, all flex cables etc. Interestingly enough, the BT still did not work. The problem followed the mother board. All other components worked, including the 3G card which is a USB device on the same USB hub as the darned bluetooth. :wtf:

How could the NEW 3G card operate and not the NEW BT module sitting on the NEW PCI-E assembly? Could they run on different voltages from the main board and could only one voltage was missing?Hmmm...

I got plenty of great advice from Shawn in the troubleshooting process, and after some great discussion Shawn pointed me in the right direction, FUSES!

Fuse F5, shown in the attached image, appears to be powering a 3.3v line to the PCI-E subassembly. I guess the 3G card runs off 5v and somehting else, and hence a blown F5 only knocks out the BT. It is hidden underneath the flex cable to the PCI-E subassembly.

I shorted F5, and got my BT back.

So how did it happen?
Here is what I think: MHF coax connectors for the antenna cables are usually located on the board so that the connector does not short components on the board. Usually. The Bluetooth board is an exception. If you do not position the plastic properly under the neck of the coax connector/cable then the shield of the connector will short stuff on the bluetooth board. Lesson learned- be very careful to place the plastic between the board and the coax cable.

I big thanks :cheers: to Shawn for all the help! :notworthy:


File comment: Location of fuse F5 on Mainboard.
toughbook_Bluetooth.png [ 979.16 KiB | Viewed 4144 times ]

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