Among other issues with this 7603 were the Z axis operation, it seemed
like a blanking issue (beam is not blanked correctly), but on closer
inspection it is a bit more involved:
The intensity control works reversed (fully CCW is maximum intens, fully
CW blanks the beam). This is not a cabling issue.
Blanking signals are correctly processed by the Z axis logic, and the Z
axis amplifier produces the correct voltages on pin B (about 20 V with
P1171 open for a blanked beam, and about 90 V with maximum input current
for maximum intensity). I also cross checked this against a working 7623
just to be sure that I analyzed the circuitry correctly and understood
the circuit description.
So the inversion must happen somewhere else. I previously replaced all
HV caps in the HV unit, including the DC restorers. Now I also replaced
all diodes in the grid DC bias restorer. No change in behaviour.
The focus amplifier, preset and front panel control all work correctly.
I don't know what else I could check or what else could cause this.
Maybe someone here has another idea?