Why don't you put it up on eBay as a Special Edition Soft Focus SL66 that has been known to have the image of the Virgin Mary show up in negatives that include large amounts of blank sky.
Other things to check....
What aperture do you shoot at? Try taking the same picture at different f-stops and comparing to see if there isn't something revealed by that. Perhaps they will be sharp at some apertures but not others. Are you using a 220 or 120 back and does the film match the back (e.g. are you putting 120 film into a 220 back)? Was theu tester-guy's laster our of alignment<g>? Are you wearing galsses when you look at the prints?
One more thought, Leon. You might also check the film path, rollers in particular. There might be something stuck to a roller that is causing the film to buckle behind the gate.
thanks for all the suggestions guys
The enlarger is fine - good solid double glass carrier with spirit level checks of baseboard, carrier and lens plane before each session. Old negatives are giving me good sharp prints
mikewhi ... sl66 backs are adaptable between 120 and 220 at the flick of a switch -i cant use 120 at the 220 setting, so I dont think thats it.
Ralph - The film holders look fine ... I'm getting the problem using both of my two backs so unless they both have the same alignment issues ....?
I'm reliably informed that both the focusing screen and film plane alignments have been checked with no faults showing ... so???
what a nightmare!
Leon, could I ask you - with how many lenses is this problem happening? Have you previously had good results with these? If a fine-quality lens delivers duff performance but looks OK, this usually points to its having had a generous thumping, leading to misalignment.
I once had an f3.5 50 mm Leitz Elmar, made just after the war, which looked totally mint. I even spent money having a small scratch polished out and looked forward to using a perfect specimen of a legendary lens. The results was very poor, I sent it to several expert repairmen for a collimation check, it turned out the lens had been a dog since the day it was made! Probably an inaccuracy in the basic grinding of the elements, which you really wouldn't expect of Leitz (or Zeiss!).
Could the Focusing screen be installed upside down?
I believe these questions may have been addressed previously, but:
Do the images remain unsharp when you change lenses?
Is there any indication of a loose element or de-bonded/separated element in your lens?
Have you checked the image sharpness at the focal plane with a ground glass and magnifier? Then compared this with the image on your focusing screen?
I had a similar problem which Oceanside Camera Repair (now out of business because of old age), traced to some bushing to do with the focusing track. He replaced it, and no futher problems. As I remember, he told me this is not uncommon, but can not be diagnosed without dismantling the camera.