"Mark Zacharias" wrote in
.com:

"Geoff" wrote in message
...
I have a tek 2215A CRO with following fault..
Left side of trace has a ripple, about 1/2 division vert
amplitude and about 25% of horizontal is affected.
Both channels the same
When vert offset is manually swept, the pattern of ripple
changes, still both channels the same
Timebase does not change shape or size of ripple
ripple is 1/2 or 1 cycle but is like someone has put a magnet on
the side of the tube.

some CRTs had tiny magnets (0.1" dia.) glued on at the factory,for beam
alignment.
one could have come loose.


Changing attenuator makes no difference.
Was OK a few months ago when last used

If this is a tube fault, I will junk it, what do others think?


Always start with the power supply.

Yes,PS filter caps,and other decoupling caps on the boards are a problem in
aging scopes.

Mark Z.



to check tube geometry,input a 6 div high signal with a fast rise time(like
a square wave or time marks),one cycle per division,and turn up intensity
to see the fast rise.
if the tube is bad,you'll see distorted lines.
the distortion remains in the same place as you move trace position
controls.


IMO,2215-series are good scopes,easy to repair.
I have a 2213,one that I built myself from boards discarded by other techs.
Scored a second-grade CRT from the head of CRT mfg,bought the little bits I
needed to finish the scope for about $20.

good analog scopes are hard to find these days.

--
Jim Yanik
jyanik
at
localnet
dot com