giannibo wrote in
:



Infact: all IC are custom, with various models.Now I am arrived to
have: trace very weak, but seem trigger and vertical work.There is a
problem: the trace is only present on central zone of tube. I never
seen a wiew like this.

It could be a HV problem like loss of anode supply(usually bad HV
multiplier),or a loss of a power supply rail that supplies the deflection
output amps.(much less likely)


I fund another mainframe so I can replace step
by step the circuit, so I can see which one is defected.
But really this is on very bad conditions. I repaired a lot of
465-475-7704-7603 and others , but this is very hard!!


TEK series-resonant power supplies used in the 7704A,7904,7104,485 are very
complex and hard to repair.Many TEK service techs had hard times with
them,often just put in new PS assemblies.(not possible anymore...)

the manual's circuit description is VERY valuable in understanding them.

--
Jim Yanik
jyanik
at
kua.net