Did I fry my MAX3485 3.3v Because I used 5vdc Supply?

[K1JOS]

I needed to set up a RS485 2-wire for 3.3vdc MPU I/O to the RX/TX pins.  I bought the MAX3485 but inadvertently powered up Vcc at 5vdc instead of 3.3v.  Now I see 2.6Vp-p signals on one of the differential lines but only 400mVp-p on the other differential.  The datasheet says the chip can take a max of 7vdc supply.    I have changed (and removed) the bias and termination resistors but no change in the very low differential line.  Like an idiot I only bought the pair I needed (another week wasted) ... could this be anything other than a bad chip?   

[bobcat]

Most likely the chip is bad. The 7volt maximum rating is for static operation (no signals) or very short time duration. On the order of milliseconds.
To test just the output, you can remove the transmission line and terminator. Put a 330 ohm resistor on each output to ground. Then test again. If it seems to work, then maybe there is a problem with the terminator or cable or other component.

[K1JOS]

Thanks for the tip.  One chip worked fine on both differential lines and the other was completely dead.