vic wrote in
:

Hi,

I recently bought an oscilloscope on eBay, and I don't know if the
seller lied in the description or if it was damaged during the
transport, but the trace is completely distorted and shows strange
grid-like patterns. I made a few pictures and a little video :

http://img222.imageshack.us/img222/1984/focused.jpg
http://img212.imageshack.us/img212/6566/unfocused.jpg
http://www.youtube.com/watch?v=c5RTaTM0tJk

The shape of the trace changes when I change the y-position dial. This
makes me think the problem is in the tube and not in the electronics.

I'm wondering if this could be caused by a bent grid somewhere in the
tube ? Could it have been damaged if the oscilloscope received a shock
for example ?

Oh,yes,seen lots of them.
I worked for TEK 21.5 yrs,Indy and Orlando service centers.

I think the tube is pretty much toast, as well as the scope since there
is no way I could find a replacement tube (Tektronix 2225),

don't be so sure;Ebay or Sphere in Canada may have parts.

but I
wouldn't mind to be proven wrong :-) Thanks.

IMO,the CRT is toast;judging from the bent trace and glow on the left side
of the graticule.But you should check the power supplies anyways.
That's always step ONE.

FYI,checking tube geometry is best done with a signal displayed.
Then you can see the vertical distortions.

If you do remove the CRT,tilt it and see if you hear little bits tinkling
inside,that's from the electron gun glass rods that got cracked.Sometimes
you can see them on the faceplate,or they make spots on the graticule.

--
Jim Yanik
jyanik
at
kua.net