I was given a inoperable Tamron SP 24-135mm f3.5-5.6 Aspherical AD (IF) lens. Looks just like new but the aperture starts to open and close very fast at various zoom settings without pressing the shutter release. Probably opening and closing about 4 cycles per second. It then locks up a 30D or EOS 3 when the shutter release is pressed. - What would be the maximum you would pay for repair before just scrapping the lens? - How is the IQ and build quality? - What have been your repair costs of like or similar Tamrons for various problems? - Anyone ever had this problem?