georgekok97
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Good or bad psu ? help..

Mon Dec 31, 2012 4:13 pm

hi !...
i bought a psu 5v 2A from a local store and when i measure the tp1 and tp2 voltage it shows 4.65v ...
i know that it should be from 4.75v to 5.25v but it can power my raspi with my wifi (tp link wn422g) ... should i keep using it ?? can it cause to my raspberry any problems ? And finally can someone to suggest me a GOOD and if possible cheap psu(EU) from ebay ??

thanks, georgekok97...!

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Burngate
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Re: Good or bad psu ? help..

Mon Dec 31, 2012 4:33 pm

4.65v won't hurt anything, so if it does what you want, then keep using it

The most reliable information we have is that the Pi itself will keep working down to almost 4v, but in general, USB devices will start to complain well before that.
If your wifi dongle seems to be happy, then you're ok

georgekok97
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Re: Good or bad psu ? help..

Mon Dec 31, 2012 4:37 pm

a good trusted known psu ???
that gives 5v+

l0lzhax0r
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What

Mon Dec 31, 2012 6:14 pm

What
Last edited by l0lzhax0r on Fri Jun 06, 2014 10:30 am, edited 1 time in total.

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pluggy
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Re: Good or bad psu ? help..

Mon Dec 31, 2012 10:34 pm

Does it have a fixed lead or a seperate lead with a USB socket ?. Have you measured the voltage both sides of the F3 polyfuse ?. Some Pis appear to have polyfuses that are a bit high resistance and drop the volatage quite a lot. But, if its doing the job, I'd tend to leave it alone.
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

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johnbeetem
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Re: Good or bad psu ? help..

Mon Dec 31, 2012 10:48 pm

pluggy wrote:Does it have a fixed lead or a separate lead with a USB socket? Have you measured the voltage both sides of the F3 polyfuse? Some Pis appear to have polyfuses that are a bit high resistance and drop the voltage quite a lot. But, if its doing the job, I'd tend to leave it alone.
Some Micro USB cables have very thin conductors and have substantial voltage drop. The best way to find out which components are dropping voltage is to measure 5V at the power supply and on both sides of F3. There are useful instructions for this at the RasPi Troubleshooting Wiki: http://elinux.org/R-Pi_Troubleshooting# ... r_problems

That said, if 4.65V works you shouldn't have to do anything. I was doing fine with 4.65V before I switched over to a Motorola Atrix Lapdock which gives me nearly 5.0V. You'll use less power at 4.65V and run cooler since 3.3V regulator RG2 won't have to convert as much voltage to heat.

georgekok97
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Re: Good or bad psu ? help..

Mon Dec 31, 2012 11:33 pm

pluggy wrote:Does it have a fixed lead or a seperate lead with a USB socket ?. Have you measured the voltage both sides of the F3 polyfuse ?. Some Pis appear to have polyfuses that are a bit high resistance and drop the volatage quite a lot. But, if its doing the job, I'd tend to leave it alone.
johnbeetem wrote:Some Micro USB cables have very thin conductors and have substantial voltage drop. The best way to find out which components are dropping voltage is to measure 5V at the power supply and on both sides of F3. There are useful instructions for this at the RasPi Troubleshooting Wiki: http://elinux.org/R-Pi_Troubleshooting# ... r_problems

That said, if 4.65V works you shouldn't have to do anything. I was doing fine with 4.65V before I switched over to a Motorola Atrix Lapdock which gives me nearly 5.0V. You'll use less power at 4.65V and run cooler since 3.3V regulator RG2 won't have to convert as much voltage to heat.
the psu has on it a female usb ....
in the one side of the polyfuse is 5.03v and on the other ~4.69v ....
is that a problem ??

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pluggy
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Re: Good or bad psu ? help..

Tue Jan 01, 2013 12:06 am

If it isn't causing problems, no. Theres nothing wrong with the PSU or lead, the voltage drop is due to the polyfuse. Low voltage tends to cause problems with USB devices first, since the SOC uses 3.3 volts and less internally. If the Pi is stable and everything works I wouldn't worry about the voltage.
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

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