Request urgent help , newbie Raspberry Pi ModelB issues

If it booted properly the first time using Wheezy, perhaps it would be worth trying that again as a first step. It might be that you changed something in that first run that damaged the image.

If that doesn't work, I would try another SD card. I have found that some cards fail in the Pi after several boots, although they appear to still work as storage devices in a camera for example.

Chris

Have you checked your setup against:

if that were a hard disk, Id say it was gone missing in action.

Definitely worth trying another SD card.

I had all kinds of trouble getting an XBMC release to work on a RPi B model

1. My trouble turned out to be power even though I was convinced it couldn't be (and was getting furious at the various web sites and fora that insisted it was.) I was using a recommended-for-RPi 5V 1A switching wall- wart power supply, and when I finally put voltmeter probes across TP1 and TP2, the supply was only delivering a hair over 4V. Using my own 5V regulator box fed by a 12V 1.6A wall-wart is allowing things to go. Raspbmc is loaded and running.

Symptoms were: live HDMI screen but dead keyboard and mouse, dropping ethernet connections, even read failures on the SD chip. The power light was always lit, but didn't mean anything.

I mention this because I remember how sure I was that power was NOT the problem. You probably should do some organized tests to rule out power trouble, or confirm it.

Good Luck, Mel.

I've been using these 5 V, 2 A units without problems:

I learned from 3.5in floppy discs that unbranded media are usually a waste of time and money. With cameras, sound recorders, and now the Pi, the same names keep coming up as reliable: Sandisc, Integral, Lexar come to mind.

As someone else suggested, check the supply voltage.

The first thing I do with any new flash storage is test that it has the capacity it claims. This is especially important if obtained online.

Agreed, I use h2testw for that purpose, and it tests the speed as well:

Usually the problem in such circumstances is not the power supply, but the micro USB cable to connect it to the Pi. I cut open a 'genuine Nokia' cable (obtained from eBay) which turned out to have no screening and about three strands of hair-thick copper inside. An 'official' Pi USB cable from Farnell was much better.

Theo

FWIW We've not had any trouble with USB cables from phones (not Nokia though). However we are now using an official Pi cable from Farnell too.

I know the importance of the power supply. I am using a 5V 1.25 Amp power supply. As a test I soldered two leads near the output (just before the output USB socket) and during boot up, the output voltage varies between 4.88 and 4.97 V. I then tested at TP! and TP2, and the voltage was identical. As an alternative, I changed to a another power supply with current rating of 3.5 Amps and the behavior of the Raspberry Pi was the same.

You're right. That sure looks ruled out to me.

(I have bad karma lately for power. Just now a circuit with an AVR and a PIC and a little audio amp took to going wild. As it happens, the battery had exhausted to the point where with loud noises the regulator couldn't maintain the PICs brownout reset voltage. But that's off-topic here.)

Mel.

Beyond a point, the current rating of the PSU isn't going to be relevant due to the 700mA polyfuse on the Pi's µUSB power input port.

Gordon

One of the problems with just measuring the voltage with an ordinary meter is that current spikes which could cause a significant brief drop won't be registered. This is particularly relevant if the connecting lead is rather long or very thin.

These spikes shouldn't really occur as the on-board filtering should deal w ith them, but what should happen and what does happen are not necessarily the s ame!

That is true, and adds to the confusion. A lot of Raspberry Pi Web sites recommend a power supply with current output rating of >= 1 Amp. So, as one of the other posters have stated, one is left with no option but to short out the resettable fuses.

... unless the fuse is effectively a slow-blow type, where it will let higher current flow for short durations. If that is the case, the power supply would have to be capable of supplying the peak current, but the fuse would be rated for the average current.

HTH

One reason for using an overrated power supply is to improve regulation. The supply will only supply the current demanded by the equipment connected to it, so a 5V, 15 amp supply will only be supplying 500mA? when the Pi is connected. It has 14.5 Amps in reserve, so you could connect up to another 29? units to it.

Unless the connected equipment is badly designed, and having an input fuse that is too small is an elementary error, you shouldn't need to, and in fact shouldn't anyway, bypass any internal protective fuses. If the internal fuses are blowing, that is an indication that the fused unit is either faulty, badly designed, or has been modified in a badly thought out manner.

Or that USB-powered accessories are being plugged into the rpi - that power is added to the rpi's own consumption. That's why a separately-powered hub is needed in most cases.