Having owned many Mac amps, I can tell you there is indeed something wrong with your control knob. It has click points for meter-hold, and regular meter swing. Also, your lights are out on your meters. I have never seen it possible that you could adjust the lights. You can get a manual from Mac for around $12, or there are several for sale on E-Bay.
mcintosh 7270 questions
just picked one up used.....What does the knob that reads "watts--hold" do?(no manual)...the knob on mine spins freely with no stop/starting point. Is it broken?....both of the VU meters don't light either-can they be turned on and off? the amp seems to work fine(haven't incorporated it into my system yet)......Can't seem to find any free info on the net...any help appreciated-thanks