Typical restance values for these types of fuses.Bigwol wrote:Having unpacked the Pi - it's clear that even after supplying a duff Pi in the first place and being given the high resistances of F1 and F2 as the reason for return, no effort is made to ensure that the replacement is any better - the seals on the anti-static bag and packaging were undisturbed, and the resistances measure even higher on the replacement Pi.
F1 = 8.0R
F2 = 5.7R
F3 = 0.5R
I haven't even bothered plugging it in, and I'm going shopping for a powered USB hub.
Unfortunately not. The D-Link hub uses the presence of the +5v line to swap between "charger" mode and "hub" mode. With no +5 all you get is 1A power on the first two ports and no hub functionality on any of them.rurwin wrote:Is it possible to disconnect that 5V from the D-Link?
it begins to look like there are other problems than power. The trouble is that it takes a lot of doing to conclusively rule out power.piglet wrote:I still don't understand why putting power into a hub attached to one port will stop the devices on the other port attached to a powered hub from working. Same result with 2 different sources of power.
That's probably fair comment and many desktop users turned their machines off overnight so few would likely ever see the problem.rurwin wrote:In about 2000, Microsoft fixed a bug that had first been introduced in Windows 95, where any PC left switched on for over 49 days would crash. It had taken them five years to find the bug, presumably because up until then all PCs crashed before that point due to other bugs.
Hi Simonsimonbr wrote:Hi,
For the last few days I was trying, in vain, to get my wifi dongle (RT2770 based) to work. But all the erratic behaviour I was seeing vanished after I ran a wire from the Raspberry Pi 5V input to the USB sockets pins 1 (effectively bridging the fuses).
1. If you can't get your wifi dongle or other USB device to work with the Raspberry Pi, you might be able to fix it by bridging F1 and/or F2
2. Current limiting on the USB ports (its implementation or even having it at all) may need to be rethought.
That may work fine, but be aware that the microUSB connector is usually rated for somewhat under 2 amps. If you push the current rating I would expect the connector to get hot, and also perhaps have more voltage drop than expected. If I was going to do this much rework on the PCB, I think I'd also add a different input power connector like a 2.1/5.5mm jack (of course, then it's up to you to make sure the voltage and polarity is also correct!)ianwill wrote:My fix
For my pi is to remove the 2 x 140mA usb fuses and replace them with 500mA. I will cut the track and link the power from the mini USB side of the main fuse via a schotky diode.
This will make the USB ports power independent of the pi power.
So long as the external input power supply source can deliver 2 amps it will be perfect.
I've been generally OK with the Logitech keyboard and Dell mouse, as long as the power suplly is up to the job (i.e. a cheap chinese 1A power supply fails, but powering from the USB port of my dekstop is fine). Tried on 3 different Pi's with different USB combinations ,no problem.Mattylad wrote:Problems like this and how many units have been shipped?
Are the foundation team having any of these problems? and is there another model to be made that changes how the USB is powered?
You need at least a keyboard and a mouse, so anything more and you will need a (powered) hub.Model A has one USB port and Model B has 2. Beyond this, mice, keyboards, network adapters and external storage will all connect via a USB hub.