Hi Tom,
That occurred to me earlier, it is -970V, which seems a little
low, but there is no information on tolerance. I measured it
with both a 20M DVM, and a 200M 410C.
It would be nice to know what others measure.
It is on my list of things to try to make right before I give
up on the CRT.
-Chuck Harris
Tom Miller wrote:
toggle quoted message
Show quoted text
How about the -1kV supply to the PDD electrode? It is regulated mostly by four series
200 volt zeners. If one of those were shorted, it would lower that supply and affect
the geometry adjustment. You can check it on J4391 on the A9 HV board.
Regards
On 3/13/2019 9:54 PM, Chuck Harris wrote:
I tried pulling the plug on trace rotation, and on
y-axis rotation, and the only effect was the trace
rotated one line width clockwise.
I guess that eliminates them, and any fringing effects
from the current in their shielded wires as they pass
down the CRT's funnel section under the mumetal shield.
What I am seeing is pretty much exactly what I would
expect to see if the box lens got moved off axis a little
bit. A hard hit on the bottom (top?) of the scope might
do that, I suppose.
-Chuck Harris
Chuck Harris wrote:
I did take the CRT out, and did not see anything
rattling about inside the shield, but it is possible
that a magnet could be stuck up in there somewhere.
The trace rotation could be eliminated by pulling
its plug. I have been meaning to try that, but
keep forgetting.
If you hold a magnet anywhere near the screen, the
trace moves drastically. Which you might expect
as the speed of the electrons from the MCP to the
screen isn't all that fast.
-Chuck Harris
Ed Breya via Groups.Io wrote:
I see that possibly adding correction magnets to fix the problem has been
mentioned here somewhat. Here's another idea, that may seem far-fetched, but not
impossible: What if the 2467 CRTs originally did have small tweaking magnets
attached, to assist in geometry. What if the adhesive or tape or whatever used
became ineffective after many years, and let go, so the magnets would come loose
and stick somewhere, like inside the mu shield? t wouldn't be obvious, because it
wouldn't be rattling around loose inside the scope.
Has anyone seen any sign of magnetic assistance on these CRTs, or anything in the
manuals, etc? Just wondering.
One other far-fetched one: Is there any possibility of the trace rotation coil
popping out of place, putting it off-axis?
Ed
