problems with voltage output

Hello,
I am a newcomer to this forum and to arduino.
I recently connected a 12v adapter to the board as an external power supply,but unfortunately it was giving out a 260v DC which I noticed later.
now the 5V and 3.3V pins are giving 8.3 and 5.76V respectively when I connect it to a laptop through USB.But the USB can give a max of 5V.
I dont know what is happening and what is wrong with the board.
I am worried a lot and hope someone can help:/
Thank you.

Did you hook the 12V up with polarity correct? Sounds like you may not have and cooked something.

Is your meter broken? How are you measuring these voltages? Do you have a alkaline battery you can measure?

260V DC in would cook the on-board regulator and blow the caps (silver cans by the DC jack.)

I had hooked it up correctly.But the DC voltage it was giving out was 266V.
I use a standard multimeter to measure and I am sure it is in right condition because it shows other voltages correctly like across a std 1.5V eveready alkaline battery.
Maybe the chip didnt fry out coz i had not connected it for too long.......Yesterday I tried it again the 5V pin was giving out a whole range of voltages from 8.3 to 2.66.Also the onboard LED,s 13th and the power one are working fine,but only dimmed out as the voltage Vcc measured across 7th and 8th pins of the Atmega328p dropped to under 3V.
I am surprised about one thing...How can output of >5V appear when the input from the laptop is a max 5V?
I am not able to find out what and all has fried up:/
But I am sure that the arduino programs like the LED blinker are working fine.
Can someone help me on how to get it serviced or should I buy a new one :roll_eyes:
Thank you.

.How can output of >5V appear when the input from the laptop is a max 5V

Quite simply it can't, so the error is not where you are looking. My bet is your meter is switched to AC.

Heyy no dude I am pretty sure it is in AC mode,I measured other voltages and it is showing fine.
The on board Leds have become dim now and whenever I connect the multimeter leads for mesuring they brighten for a second and again go dim,this is when the voltage Vcc in the Atmega 328p is below 4V.
thank you.

Nothing you are measuring makes sense. Either: you are measuring wrong, your meter is broken, or the laws of physics don't apply to you. Despite how many times your parents told you the last one, I find it hardest to believe.

Ok I will try the USB on another laptop and tell you.

Heyy no dude I am pretty sure it is in AC mode

Yes so am I, the problem is that it should be in the DC mode.

Heyy sorry guys the multimeter is not working properly I checked it now again :~It is showing a higher voltage for every voltage.
sorry again :~

I will get it repaired and then update about the voltages.Btw sorry there I had meant "not in AC mode" :stuck_out_tongue:

One more thing I noticed was the voltage across the caps(silver cans) was also the same 8.7V....should it be like that.

As your meter is broken it could be anything but those caps have the supply voltage across them.

Yeah exactly :)but should it be like that.......I am very much worried if anything has happened to my arduino,so am asking :roll_eyes:

You put 260V DC into an arduino and you are worried about that. It is a mirical that it is not burnt to a crisp.

But I can see it blink right in front of me :PMaybe that 266V was also a multimeter error :stuck_out_tongue:
what say?

I am also surprised as I can see it blinking here,the arduino should have been cooked by such a voltage :Pmayb that 266V was also junk by the multimeter......

rakshith:
Yeah exactly :)but should it be like that.......I am very much worried if anything has happened to my arduino,so am asking :roll_eyes:

Get a new meter (with new measurements) and then ask questions about what might have happened.

Funny, I first misread his post to say 2.66VDC Not 266..

I had a digital meter that was giving garbage readings like that. Turns out the 9v battery dropped to 4v...
Try changing the battery.