The ps voltage was a bit high but not enough to push the corona voltage from
5.55KV to over 8KV. The preset only varied it a few hundred volts. Put a
dropper in line and its now 5.8KV and working , subjectively, just as
before - lines on the paper image. But these lines are no longer "burned"
onto the OCD. Previously if you removed the corona housing and wire, then
the lines still emerged onto the paper for a number of runs because of a
build up on the OCD, that failed to clean off with AC and wiper blade.
Now if you remove the corona the next output is plain white so the cleaning
process can now cope with it.
I tried changing the corona housing to a spare one but the lines are in
exactly the same place. It is difficult convincing myself that the toner
lies in fine lines on the OCD as there is no obvious repeat, coincident with
the lines on the paper. There are hundreds of such fine lines with nothing
making the most persistently tranferrd ones stand out.
If the following makes no difference I will try the earlier OCD that worked
fine but the original owner managed to scratch numerous deep lines axial to
the drum so produced heavy black lines obscuring the image. If the lines
stay in the same position then it will be a total mystery as I've cleaned
,twice now, all surfaces near the OCD path. I should have said these
present lines are so fine they are just intrusive rather than blocking
information.

Going back to my original thinking, as this all started about coincident
with forced change of toner supplier. I made up a test batch of some of the
toner mixed about 2 :3 of charcoal sieved down to 75 microns, the thinking
is it would dilurte an excess of oil/styrene. It takes a while for this to
work through the feed system but so far the ratio of blackness of wanted
image to tram lines has improved, I think. I can get hold of styrene and
have plenty of silicone oil but how do you mix 98 percent sieved charcoal
with 2 percent or so of liquids without clumping? At this rate I may as well
try formulating my own toner . My set of old brass lab sieves go down to 75
micron, any ideas for a source of mesh of order 30 or 40 micron?