Jim thanks for your post.

It was a combination of items - all in the area you were pointing to! I
was looking round trying to think what was wrong - when I spotted item 1
below (and cursed myself for not spotting it last night).

1. The previous owner had fiddled with the mains transformer jumpering
(presumably to try to compensate for the dying e-caps) and the UN-regulated
+30V line was *rather* high. Setting the jumpers to local supply voltage
brought that back into line (and the regulated lines were still spot on).
The +30V was driving the oscillator in the HT ... which was affecting
cathode AND grid voltages.

2. Dug out HV probes, and HT was now rather low (thinks - someone tweaked
this after fiddling with the trafo jumpers). Re-set cathode voltage
to -2.5kV.

3. Adjusted grid cut-off (the coarse adjustment you refer to below)
according to calibration procedure in manual.

And NOW everything seems to behave properly. Or almost - there's *slight*
drop in trace intensity over the first 20 minutes of use - but I can live
with that.

PS Oh yes. I did re-check the calibration afterwards, and (not
surprisingly) did need to make some minor adjustments on the main X and Y
amps (the ones directly driving the plates on the CRT).

All's well that ends well

Dave
"Jim Yanik" . wrote in message
.. .
To control display intensity,the CRT grid gets biased more negatively than
the cathode,and to 'unblank' the CRT,the grid is moved in a positive(WRT
the cathode)direction.These are high voltages,perhaps -2KV or more.

Etc. - deleted-
Jim Yanik
jyanik
at
kua.net