is my Arduino dead?

I have two identical units I hav built that run off of battery power to the VIN. One is a back up for the other. I have been using them for a while now but did some component changes last night and I did something wrong I guess. Not sure what though. I run a servo off the arduino nano and when I powered it back up, the servo was very eradic. I tinkered some and it still was so I plugged it into USB off the computer and it worked OK. So I tried the back up and got the same response. Today I redid all the wiring and now I can not get either device to power up from the VIN but both work fine from the USB. I am guessing I fried the regulators on the Arduinos? I have tested voltage and I have 4.3 to VIN and checked the 5V pin while power from VIN is powered and have about 3.8 volts there.

Yup.Regulator is fried.
One complaint however.
It isn't exactly easy to read what you have said.
Your English isn't good at all.

Anyway check the backup one to see how many volts come from the unmodified arduino to check if the "dead" one is working correctly.
If the voltages aren't the same then the regulator has died.

Your English isn't good at all.

Holy Crap on a Cracker.... so good English is a pre-req for being allowed to post here now?

Wait, you said your battery is now 4.3 volts? Get new batteries. What kind of batteries are you using?

I run a servo off the arduino nano and when I powered it back up, the servo was very eradic.

When you say "run a servo off the arduino" you mean actually supply the power, not just control it? If so, for a start you might want to change that and give the servo its own power.

Sorry, i was not very clear last night i guess.

I control the servo with the Arduino. It is powered from an external 12 volt regulated source that is puting out a constant 6.5 volts. At the VIN it is only reading 4.2 volts however.

The servo is powered seperate from the Arduino off the same regulated external power source.

How hard is it to change the regulator?

As I stated, the operational unit and back up are both having the same issue now. They both work off USB power but not off VIN supplied power.

msumrell:
Sorry, i was not very clear last night i guess.

I control the servo with the Arduino. It is powered from an external 12 volt regulated source that is puting out a constant 6.5 volts. At the VIN it is only reading 4.2 volts however.

The servo is powered seperate from the Arduino off the same regulated external power source.

Sorry but those statements are very confusing and even contradictory. Your going to have to do better to get any useful help. Maybe a posting a drawing would help?

Lefty