Re: TEK 532 --


David Sligar
 

Hi, Cliff --
I did this, sawtooth out jack is steady at ~ 19 volts, delayed gate out, zero. I switched to "Single Sweep" (speed at 1 cm/sec) and saw the spot move to the right -- once. After a few seconds, spot is stationary, whether on single sweep or normal. Looks like the problem is solidifying. Are these clues?
Thanks!!
David

--- In TekScopes@..., Cliff White <w5cnw@...> wrote:

If you connect a dc voltmeter (preferably analog) to the sawtooth out
jack, then set the sweep speed to the slowest it goes, can you see the
voltage changing as a ramp? You might also try the same thing with the
delayed gate out.


Respectfully,
Cliff White, W5CNW
w5cnw@... <mailto:w5cnw@...>
On 04/11/2013 12:19 AM, d.sligar wrote:

Hi, Cliff --
No trigger setting has any effect on the beam (spot). No settings were
changed from the day before, when I used the scope normally. The sweep
just wasn't there Friday morning when I powered up.
Thanks,
David

--- In TekScopes@... <mailto:TekScopes%40yahoogroups.com>,
Cliff White <w5cnw@> wrote:

Did you try setting the trigger to line or external?

Respectfully,
Cliff White, W5CNW
w5cnw@ <mailto:w5cnw@>
On 04/10/2013 10:04 PM, d.sligar wrote:

Thank you, Steve.
Just one comment, I have a dual trace plugin (53/54 K) as well as the
53/54 C. Neither of these gives a sweep, so I maybe can eliminate the
pickoff circuits. (?)
Otherwise, I'll try what you suggest. I do think it's too soon to see
this one ascend (descend?) to scope heaven.

I feel a bit over my head with this, but I'm not ready to give up.
I'll let you (and the group) know how things progress.

Thanks again!

David,

A second scope would be very helpful, but you may be able to
do some
things without it. Selecting a very slow sweep speed (1 div/sec)
would
allow you so see the sawtooth on a DMM.

First you need to isolate the main area not working. It could
be at
least three -- trigger, timebase, or blanking. Turning the Trigger
Stability control to the far right should force the scope to free
run.
This does not isolate the trigger circuit however. It only
biases the
multivibrator in a way to have it reset when the sweep length
comparator trips at the end of the sweep.

With another scope, you can trace all of the trigger circuit
fairly
easily. I usually use line trigger mode when doing this, as I know
this gives a reliable signal, eliminating the possibility of a
problem
in the trigger pickoff circuit in the plug-in. Trace the signal
through the comparator(V308), and verify the Trigger level control
moves the grid voltage around (pin 9 for all + polarity
settings, pin
2 for all -- mode positions).

I was hoping to disable the unblanking pulse to rule that out,
but I
don't see a way to do that simply by pulling tube, as the
signal is
generated in a dual triode (V430B) that is shared with the trigger
multivibrator. Unfortunately, the AC coupling to differentiate the
pulse occurs before these tube stages, so there is no place
you can
easily short to ground or a supply to get a stable DC bias
voltage.

If the trigger is going through OK, then you need to focus on the
time
base. Use the circuit description in the manual to guide your
troubleshooting.

Let us know your progress. Your scope looks really clean and
is worth
preserving.

- Steve

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