Tek 7104 trace

When a Tek 7104 mainframe has no modules plugged in, should it be
possible to see a visible trace?

 

not a trace;no sweep ramp which has to come from a Horiz plug-in,thus no
beam deflection.(or positioning)

You can get a spot,though.But you need to turn up the intensity or CRT bias
for that,as you get no unblanking pulse which also has to come from a Horiz
PI.

7K mainframes were NOT intended to be operated without any plug-ins
installed.

 

In Jim Yanik typed:

Thanks. I didn't want to run it like that for any length of time --
just check if the mainframe and CRT were good. So, I take it, there is
no point in risking damage to the CRT since it wouldn't be a thorough
test anyway.

 

If you want to know if the CRT is good,then you *should* use a pair of
plug-ins;you want to adjust the intensity controls,check for double
peaking,move the trace around to check for distortions or dead or hot
spots,which indicate electron gun damage,loose particles inside the
envelope.I've seen CRTs where you could not get a straight trace,or had
particles stuck to the phosphor causing halos,dead spots,traces burned into
the phosphor,etc.Even bad geometry.