The measurements of 167 and 180 ohms are meaningless. However the 1.5 ohms after it's crashed doesn't bode well - assuming your meter is ok and you're making good contact, it says the polyfuse is half-blown. 0.1 ohms would be what I would expect for a good one.falk0069 wrote:When I measure ohms across the F3 polyfuse I see this:
167 ohms during boot up and while sitting at the login prompt. However there were a few spikes to 180 ohms. When it stops working the ohms drop to 60 for a few secs and then 53. When I unplug the Pi, it drops to 1.5 ohms.
Your original post mentions that your RPi will work again after a matter of minutes. Polyfuses usually don't recover that quickly.falk0069 wrote:Thanks for all the suggestions. It is sounding like the polyfuse is probably bad and heating it in an oven isn't going to help that. I'll give my adafruit power supply a shot once I receive it and if it doesn't help then I'll just return it.
Your RPi is defective and should be returned for replacement.Sueno wrote:My new RS supplied 512MB RPi is also cutting out consistently at between 5 and 15 mins after switch on.
I used a temperature probe to measure (several times) the Samsung RAM chip and this shows a surface temperature of 34.5 - 34.7C at cut-out. The room air temperature was 22.1C.
I then applied a hair dryer to blow room air at the chip. This was very effective as the Pi did not shut down. After ten minutes the chip surface temperature was at 25.5C where it stayed until I switched the fan off after an hour. Switching off the fan then allowed the chip temperature to rise in two minutes to 34.7C when the PI cut-out.
Although the temperature is not high, something does not like the heat. By logic that still looks like overheating to me. I'll try a passive heat sink next. If that does not work, it looks like a box with a fan is required. Pity.....
I don't run Raspbmc myself but I believe that the default installation of it does enable a certain amount of overclocking. If that is true you should disable it before concluding that your RPis are faulty and RMAing them.bercar wrote:I am having the same issue with both of my 512 PI's. All i have loaded is Raspbmc. It will boot to the menu, run normally for a few min, then if I don't do anything to dissipate the heat on IC2, it just shuts off. I do have time to load the system menu, but the temp display updates really slow.
Highest CPU temp shown through SSH is 65.9C
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