Tektronix 465 with uncontrollable intensity
 

I've got a tek 465 oscilloscope that has a weird intensity problem. On
powerup, the intensity gradually increases as one would normally
expect, but it continues to rise until the whole room is illuminated
with an eerie blue glow. The intensity knob has an effect on the trace,
but it only goes from ridiculously bright to obnoxiously bright.

At the point where I estimated I'd had my year's worth of x-rays, I
turned the power off. But I think I did check a few voltages on the CRT
circuit and didn't see anything unusual. It's been a year or so since I
have messed with it.

I have heard legends about CRT's shorting internally and causing this
problem. Is this likely in my case? And how would I verify that? I did
not observe any continuity between any of the CRT neck pins, with the
exception of the filament, of course.

Tektronix 465 with uncontrollable intensity
 

Sounds like the z amp is on the fritz, but I don't know that 'scope well.
For folks who really know their Tek. 'scopes, go to the Tekscopes group on
Yahoo.

http://groups.yahoo.com/group/TekScopes/

It's probably something quite simple ...

Dave
wrote in message
oups.com...
I've got a tek 465 oscilloscope that has a weird intensity problem. On
powerup, the intensity gradually increases as one would normally
expect, but it continues to rise until the whole room is illuminated
with an eerie blue glow. The intensity knob has an effect on the trace,
but it only goes from ridiculously bright to obnoxiously bright.

At the point where I estimated I'd had my year's worth of x-rays, I
turned the power off. But I think I did check a few voltages on the CRT
circuit and didn't see anything unusual. It's been a year or so since I
have messed with it.

I have heard legends about CRT's shorting internally and causing this
problem. Is this likely in my case? And how would I verify that? I did
not observe any continuity between any of the CRT neck pins, with the
exception of the filament, of course.

Tektronix 465 with uncontrollable intensity
 

"David C. Partridge" wrote in
:

Sounds like the z amp is on the fritz, but I don't know that 'scope
well. For folks who really know their Tek. 'scopes, go to the
Tekscopes group on Yahoo.

http://groups.yahoo.com/group/TekScopes/

It's probably something quite simple ...

Dave
wrote in message
oups.com...
I've got a tek 465 oscilloscope that has a weird intensity problem.
On powerup, the intensity gradually increases as one would normally
expect, but it continues to rise until the whole room is illuminated
with an eerie blue glow. The intensity knob has an effect on the
trace, but it only goes from ridiculously bright to obnoxiously
bright.

At the point where I estimated I'd had my year's worth of x-rays, I
turned the power off. But I think I did check a few voltages on the
CRT circuit and didn't see anything unusual. It's been a year or so
since I have messed with it.

I have heard legends about CRT's shorting internally and causing this
problem. Is this likely in my case? And how would I verify that? I
did not observe any continuity between any of the CRT neck pins, with
the exception of the filament, of course.





The DC restorer diodes commonly are a failure item on the 465 scopes.
They can break down under HV,but test OK on a DMM.
If you don't have a curve tracer,just replace them.
Next,the HV caps (in the DC restorer) themselves can break down.

--
Jim Yanik
jyanik
at
kua.net