Chromatic Tuner Imt 500 Manual

When I turn the tuner on the calibration is set to 441. The calibrate button is not always responsive meaning that when I push it, the calibration number does not always increment. The tuning area simply displays a C and striking a string has no effect. In the past when this has happened I simply changed the calibration to 440 and that seemed to fix it but now when I can get the calibration to change to 440 the C is still constantly displayed.
My instructor has the same tuner but his does not have the inverted black triangle at the top of the display with the word CAL. Superimposed so I'm wondering if there is a way to turn off the calibration function. I don't have the user manual anymore and I can't find one online. With only 3 buttons the combination of buttons I can hold down to enable/disable functions is limited and I tried holding them in with no effect.
Any ideas or is my tuner f'ed? I had a Korg AW-1.
Vsco film 01 for adobe lightroom 4 5 download. Results 1 - 12 of 12 - INTELLI CLIP ON CHROMATIC TUNER - IMT 500 - With 4 Guitar Picks. Also selling Yamaha YT-120 in full working order sorry no manuals. Intelli imt-500 clip-on chromatic tuner seiko key. Korg chromatic tuner ca-30 manual guitar fender ft100. Imt-500 digital chromatic auto tuner canada chromatic.
Nice tuner, not real cheap. I kept hitting the mode button and changing it out of 440. It was very easy to do and very annoying until I figured out that it was my own fat fingers causing the problem.
It didn't have a back light. Totally useless to me in a dark room or a night jam at a festival.
Sold it a friend that loves them and went back to my IMT-500's. I understand the new Korg models are supposed to have the light.
No experience with the other. I have Intelli's in all my mandolin and guitar cases.