On my Tek 465 scope, I notice a peculiar variation of the intensity of
the trace at fast sweep rates. The intensity decreases during the sweep
for about 200 ns near the beginning of the trace and returns to normal
for the remainder of the sweep. It is most noticeable using ALT sweeps.

Please see the pictures at

http://home.att.net/~a.schapira/pix/...cope_.05us.jpg
http://home.att.net/~a.schapira/pix/...scope_.1us.jpg
http://home.att.net/~a.schapira/pix/...scope_.2us.jpg
http://home.att.net/~a.schapira/pix/...scope_.5us.jpg

You can clearly see the intensity drop off for about 200 ns and come
back up. For each picture, the inputs are the same; only the sweep
rate was changed according to the name of the picture file.
Its as if some of the sweep or trigger signal is leaking into the Z axis
circuitry.

If you could suggest a cause (and remedy) for this I would be grateful.
I do not have a service manual or schematic (I would like one), but I am
generally good at troubleshooting and repairs. I just don't have any
experience troubleshooting Tek scopes.

Thanks for any help you can provide with this.

-Al Schapira, KC2HRH,

"Al Schapira" wrote in message
...
On my Tek 465 scope, I notice a peculiar variation of the intensity of
the trace at fast sweep rates. The intensity decreases during the sweep
for about 200 ns near the beginning of the trace and returns to normal
for the remainder of the sweep. It is most noticeable using ALT sweeps.

Please see the pictures at

http://home.att.net/~a.schapira/pix/...cope_.05us.jpg
http://home.att.net/~a.schapira/pix/...scope_.1us.jpg
http://home.att.net/~a.schapira/pix/...scope_.2us.jpg
http://home.att.net/~a.schapira/pix/...scope_.5us.jpg

You can clearly see the intensity drop off for about 200 ns and come
back up. For each picture, the inputs are the same; only the sweep
rate was changed according to the name of the picture file.
Its as if some of the sweep or trigger signal is leaking into the Z axis
circuitry.

If you could suggest a cause (and remedy) for this I would be grateful.
I do not have a service manual or schematic (I would like one), but I am
generally good at troubleshooting and repairs. I just don't have any
experience troubleshooting Tek scopes.

Thanks for any help you can provide with this.

-Al Schapira, KC2HRH,


Something out of kilter in the bright-up/blanking/fly-back suppression
circuitry ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"Al Schapira" wrote in message
...
On my Tek 465 scope, I notice a peculiar variation of the intensity of
the trace at fast sweep rates. The intensity decreases during the sweep
for about 200 ns near the beginning of the trace and returns to normal
for the remainder of the sweep. It is most noticeable using ALT sweeps.


Al,

Could I can't remember if a 465 does this or not, but HP scopes of that era
would highlight the section of the trace that would be "magnified" by the delay
when you had the delay mode switch set to normal and the delay ring of the
timebase anywhere but off. Try adjusting the delay vernier to see of the
highlighted section moves.

--
James T. White

"James T. White" wrote in message
...
"Al Schapira" wrote in message
...
On my Tek 465 scope, I notice a peculiar variation of the intensity of
the trace at fast sweep rates. The intensity decreases during the sweep
for about 200 ns near the beginning of the trace and returns to normal
for the remainder of the sweep. It is most noticeable using ALT sweeps.


Al,

Could I can't remember if a 465 does this or not, but HP scopes of that
era
would highlight the section of the trace that would be "magnified" by the
delay
when you had the delay mode switch set to normal and the delay ring of the
timebase anywhere but off. Try adjusting the delay vernier to see of the
highlighted section moves.

--
James T. White



I'd say James is right on the money, this looks like the scope is in "B
intensify" mode.

"krikkit" wrote in
news:3M8gf.206044$ir4.190226@edtnps90:


"James T. White" wrote in message
...
"Al Schapira" wrote in message
...
On my Tek 465 scope, I notice a peculiar variation of the intensity
of the trace at fast sweep rates. The intensity decreases during
the sweep for about 200 ns near the beginning of the trace and
returns to normal for the remainder of the sweep. It is most
noticeable using ALT sweeps.


Al,

Could I can't remember if a 465 does this or not, but HP scopes of
that era
would highlight the section of the trace that would be "magnified" by
the delay
when you had the delay mode switch set to normal and the delay ring
of the timebase anywhere but off. Try adjusting the delay vernier to
see of the highlighted section moves.

--
James T. White



I'd say James is right on the money, this looks like the scope is in
"B
intensify" mode.




Then others here who own a 465 could duplicate the "problem".

--
Jim Yanik
jyanik
at
kua.net