Hello Chroma Group!

in the past few months i've been noticing that my chroma wont sound as many keys as it used too. Im pretty sure that some of the voices are out, but im at a loss as to how i can find out which ones. when i use the tune all function, the light only blinks four times, and im under the impression that it should blink once for each voice which is 6. that being said, i dont know how to find out which voices are broken, or what im even supposed to look for. i have basic knowledge when it comes to synth repair, and im hoping that this is something i can diagnose myself unless i need special tools. any help from this group would be greatly appreciated!

thanks all.