My HP iPAQ 612c cannot turn on, but when charging the red light appear..what solution can i do..?

You may follow the the link below to do reset on your HP iPAQ 612c Business Navigator.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=120&prodSeriesId=3544355&prodTypeId=215348&objectID=c01364508

I hope this works for you.

do you mean hard reset? here is how to do a hard reset: Start -> Setting -> System -> Factory Recovery Icon -> Enter "1234" -> Yes
hard reset will erase all personal data on the phone.

Hello,

You built one of these too, eh?

Yes, there can be a problem doing this. First off, 3 AA batteries does not equal 4.2 volts, they are 1.2volt nominal so 3 * 1.2 = 3.6volts. When they are just off the charger, terminal voltage will be closer to 1.5v, so 1.5*3 = 4.5 volts.

Using ohms law, E=I * R, we can find your current as I = E / R or I = 4.5v / 4r7 as .95Amps (almost a full amp) that you would see worst case. The resistor is doing nothing for you.

The reason that the charge light blinks intermittently is because the charge controller (lithium battery, right?) is pulsing due to low voltage.

Try this: Take *6*, yes, 6, AA batteries, your choice of chemistry, and put them in series. That will give you a nominal (alkaline) voltage of 9v. Connect a low dropout 5v regulator such as an LT1117-5. Then you will be able to use your battery backup much more effectively.

On a different note, I used 4xAA (NiMH) and powered my ipaq 3650 directly. Worked great. Your mileage may vary though.

In general, there's three types of charger you might need. Really ancient iPAqs used a round DC jack type charger, then there was a long time where all iPaqs used the same flat 22-pin connector. More recently, HP has moved to the same mini-USB plug used for a lot of mobile devices.

If you're really stuck, try http://www.ipaqrepair.co.uk/store.php?cat_id=25 and match your iPaq to the pictures.

http://h10025.www1.hp.com/ewfrf/wc/document?docname=bud09168&cc=us&lc=en&dlc=en&product=58123

go through the above link, it shoud resolve your issue.

I've decided to get a smartphone with Windows Mobile 6.1, so this issue has been "solved"

Hmmm...is the USB cable plugged in to a powered PC? Could be cable or battery issue. Red light means that the battery is very low on juice. Return it to where you got it from if you can't solve it on your own.
you want a repair service

Reset te unit

Hi xx

It sure does sound like a battery. If it is more than 12 months old, and regularly charged(daily) , then it will need replacement.

regards
Graeme

Failed battery pack most likely.