A normal polyfuse should have a resistance of about 0.2 Ohm, so your measurements of 1.0 and 1.3 Ohm are way off, five or even six times more than normal. In fact Tyco claims that even after several times having been blown, but given enough time to recover (days) the fuse will return to less than half an ohm (0.45 Ohm) !thogue wrote:was reading some other power threads, So i checked the fuses with the multimeter but this time checking the resistance vs checking the voltage difference.
my new pi is measureing 1.3~ ohms
my older pi is measuring 1.0~ ohms
Doesnt this mean that both my polys are 100 percent or better??
Im now confused as to why I am seeing the >.3v difference when I am running on an SD card (any of my 4 sd cards at my desk currently, SanDisk 1GB,512MB, Wintec 16GB, SanDisk 4GB micro)
Unfortunately the quoted article doesn't have any info on whether cooling a blown fuse will help it to recover faster! The physical processes involved in "blowing" are very complex. Whether cooling will help in the recovery process is frankly in doubt.psergiu wrote:Will a cooled polyfuse recover quicker ?
In theory, it should ...
http://www.te.com/content/dam/te/global ... entals.pdf
Has anyone tried putting his RPi in the freezer for 5 minutes then measuring the resistance of the polyfuses afterwards ? I would but i have a el-cheapo multimeter.
it is not very difficult to mess up with reflow processthsBavR10 wrote: This leads me to the conclusion, that there are massive differences in resistance of
fresh polyfuses, maybe there are different processes in producing the Pi's.
no that will be date of manufacturing [probably]thogue wrote:maybe im off on how these are getting distributed. I am in the US I ordered from Newark/E14 (which is a Farnell company) So I guess thats farnell
my build build date is 1228
the stick on the back I assume its a serial FN12085XXXX, my older by being in the 2000s and by newest one (the one I still havnt used except for testing per this thread) is a 3000s
Dont know if this will become relevant or not we shall see.
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