I am the longtime owner of a Teac 80-8, 1/2" 8 channel machine. I bought the machine in 1999 as a basket case. Mechanically, the machine was flawless..I have never had an issue with relays or any transport difficulties. The first issues I addressed were the heads and guides. The heads were re-lapped and laser aligned. I cut new lock notches on the rear of the tape guides so they could be rotated slightly..exposing a fresh area on the guides. I have made numerous attempts to calibrate the machine, using the original 1977 Teac calibration tape..with less than satisfactory results. Not to mention, the tape has to be baked for hours, and still sheds a bit. My problem is..I cannot get a response from the 16KHZ record eq adjustment, on any channel, even with the adjustment at max. I believe (if memory serves me), is is supposed to be -1 to -2db, but I cannot get any response. The 10K response is fine, by the way. I shelved the machine 5 years ago because I expected the performance to be superior to say, a normal bias cassette, recorded on an early cassette deck, but that is exactly the way it sounds. Ok..to the point(s) of my post. I have heard that the later Teac 80-8 had much better heads, than the earlier production machines. Does anyone know if this is fact? I do know that the head part numbers differ between early and later machines. I have a headstack from a 1979 80-8 (mine is a 76'). The later rec/repro heads have relief notches at either end of the cores, and different part numbers. Does anyone here have any sensible suggestions on how to improve performance on this beast? And please don't tell me to get a different machine. I have too much $ invested in the deck already, and the $ situation gets worse all the time. Also, can anyone point me where I can get a good copy of a calibration tape for cheap? I can't afford MRL tapes at this time. I am currently using EMTEC SM911 tapes. Any suggestions on a different tape? I really appreciate any advice you good people can give...Thanks in advance