I have this tek 465m for many years and it has always had the
following problem.

There is no horizontal sweep (either A or B) when the "var" knob
is in the calibrated position (i.e. uncal LED off). other than
that the scope works really well and other than being an annoyance
it hasn't bothered much.

However, last week last week the high voltage supply when out (the
fuse blew) and after fixing that, I wanted to dig into the horizontal
problem. I don't think the HV problem and the clibration problem are
related at all.

What I have found is this.... the switch and variable pot are OK. There
are two switch circuits, one shorts the variable potentiometer wipe to
the low contact and the other switche the uncalibrate LED. Just shorting
the wiper on the potentiometer using a jumper wire, while the variable
pot is at 25% will "calibrate" the sweep timing. It turns out that the
sweep will only work when the LED is "on". There are three LEDs which are
driven off the same power supply, which look like they are derived from
the +32V using a voltage divider, trigger, MAG10 and the Uncalibrate
LED. It turns out that if either of the MAG10 or the Uncalibrate LEDs
are on, the sweep will work. There is a small dip in the LED power
supply rail (5mV) when either these LED are on. I suspect that this
also effects something in the sweep generator.

Has anyone run into this ? I do have a maintenance manual. Unfortunately,
this manual does not have the foldout schematics and the simplified
schematics aren't relevent. Anyone know were I can get a copy of the
schematics for the relevent sections (i.e. sweep, LEDs, etc...).

Thanks, -ingo

--
/* Ingo Cyliax, , Tel: 812-391-0895 */

"Ingo Cyliax" bravely wrote to "All" (10 May 05 18:05:44)
--- on the heady topic of "Tek 465M Horizontal Problem"

Sync gate or hold off not being propagated beyond the LED logic? Trace
back these signals and where they then end up. Seems like some logic
input there is faulty.


IC From: (Ingo Cyliax)
IC Organization: Computer Science, Indiana University
IC Xref: aeinews sci.electronics.repair:47791


IC I have this tek 465m for many years and it has always had the
IC following problem.

IC There is no horizontal sweep (either A or B) when the "var" knob
IC is in the calibrated position (i.e. uncal LED off). other than
IC that the scope works really well and other than being an annoyance
IC it hasn't bothered much.

IC However, last week last week the high voltage supply when out (the
IC fuse blew) and after fixing that, I wanted to dig into the horizontal
IC problem. I don't think the HV problem and the clibration problem are
IC related at all.

IC What I have found is this.... the switch and variable pot are OK.
IC There are two switch circuits, one shorts the variable potentiometer
IC wipe to the low contact and the other switche the uncalibrate LED. Just
IC shorting the wiper on the potentiometer using a jumper wire, while the
IC variable pot is at 25% will "calibrate" the sweep timing. It turns out
IC that the sweep will only work when the LED is "on". There are three
IC LEDs which are driven off the same power supply, which look like they
IC are derived from the +32V using a voltage divider, trigger, MAG10 and
IC the Uncalibrate LED. It turns out that if either of the MAG10 or the
IC Uncalibrate LEDs are on, the sweep will work. There is a small dip in
IC the LED power supply rail (5mV) when either these LED are on. I suspect
IC that this also effects something in the sweep generator.

IC Has anyone run into this ? I do have a maintenance manual.
IC Unfortunately, this manual does not have the foldout schematics and the
IC simplified schematics aren't relevent. Anyone know were I can get a
IC copy of the schematics for the relevent sections (i.e. sweep, LEDs,
IC etc...).
IC Thanks, -ingo

.... That was a fascinating period of time for electronics

In article ,
Asimov wrote:
"Ingo Cyliax" bravely wrote to "All" (10 May 05 18:05:44)
--- on the heady topic of "Tek 465M Horizontal Problem"

Sync gate or hold off not being propagated beyond the LED logic? Trace
back these signals and where they then end up. Seems like some logic
input there is faulty.


thanks for the pointer...of course, the last time I worked on it,
the -5V supplied stopped working and then the main fuse blew... so
now I have some power supply work to do, before digging into that
problem again...

Later, -ingo

--
/* Ingo Cyliax, , Tel: 812-391-0895 */