Hi Leo,
Thanks for doing the test. The problem with making
measurements in the focus area of the 2467B is the
extreme high impedance of the circuitry. Even my
100M HV probe loads the circuits down visibly.
However, the low impedance CRT voltages:
edge focus, geometry, astigmatism, PDD lens and wall band,
anode 1, are all rock solid. As is the cathode of the
CRT.
So, that points to the actual anode voltage and the
focus voltage... neither of which will behave well when
measured with any probes I have.
It would seem to me that the only way for the astigmatism
voltage required for good focus to shift would be if the
anode voltage changed.
The change in the anode voltage wouldn't necessarily cause
a corresponding shift in the focus pot's position for best
focus, because the focus electrode's voltage is derived from
the cathode supply...
Q4402 was found earlier to be shorted. It was replaced with
new. I suppose it might be a good idea to figure out how it
got to be bad. Perhaps a problem with C4403 did the deed?
Puzzling.
-Chuck Harris
satbeginner wrote:
toggle quoted message
Show quoted text
Follow up:
After about 2h45min and turning up both the intensity and readout, the display and readout were still in the sharpest setting.
Adjusting focus and/or astig would make the screen less focussed.....
I would suggest to (before and after) check all relevant voltages on the CRT.
Geometry, edge focus, y-axis alignment, and the components around Q4422, Q4402 and Q4403.
Maybe a cold solder joint in that area?
Un saludo,
Leo
