I found the problem:
A bad batch of 35mm Tmax-400 film.
I just dev'd a roll of Neopan 400 (9 min in XTOL at 20C). It's much denser, and the used XTOL poured out of the tank water-clear instead of the yellow-orange that I've been getting with Tmax-400. I also dev'd a roll of Delta 400 a couple of days ago, also with clear developer instead of yellow-orange. The density of the Delta looks fine to the eye, but due to its high fog, density above B+F is unimpressive. Here are leader-densities of the Neopan:
Test-leader density = 2.88 (from clip-test)
Roll-leader density = 2.74 (on the roll)
Those are reasonable numbers. Here are leader-densities I got with TMY2 (6.5 min at 20C):
Test-leader density = 2.97 (from clip-test)
Roll-leader density = 2.35 (on the roll)
I think Kodak is having a problem with quality-control. This thread reports consistency problems with Tri-X:
(there was a url link here which no longer exists)
Five months ago, TMY2 dev'd in XTOL for 6.5 minutes at 20C produced perfect density, and the developer came out of the tank with only a faint hint of yellow colouration. Now, TMY2+XTOL neg's are thin, and the dev pours out yellow-orange. My home-brews act like XTOL (yellow & thin), so the problem is not with XTOL. I've systematically eliminated all other possible sources of failure (read this thread), cleaning everything, different water, different graduates+tank, etc. However, Kodak's T-grain competitors dev fine in XTOL, yet TMY2 no longer does so. My conclusion: There's a problem with 35mm TMY2 with ascorbate developers.
The codes on the boxes of Tmax-400 are: "04/2014 0166".
The 04/2014 is obviously the expiration date, and I'll guess that 0166 is the batch-number.
These were purchased over the last couple of months from Freestyle and B&H.
If you have some fairly new Tmax-400 with code 0166, could you dev a test-roll in undiluted XTOL and report on it? Also mention if it's 35mm or 120, and the amount of XTOL you used. I dev'd 36-shot rolls using 220 ml in an SS tank, and 325 ml in a Paterson -- both failed.
Mark Overton