Re: TEK 532 --


David Sligar
 

The toggle switch is "Single Sweep / Normal". Not an extra light, it's a button, label "Reset"

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

One other thing I just noticed: yours has a extra toggle switch below
the external horizontal input, and what looks like an extra light above
it. What do those labels say for those two? Mine has neither, but is
still a P11.


Respectfully,
Cliff White, W5CNW
w5cnw@... <mailto:w5cnw@...>
On 04/10/2013 10:14 PM, Cliff White wrote:

Mine's also blue, probably P11, and only says "532" w/o the 57. Strange.



On 04/10/2013 10:12 PM, d.sligar wrote:

I'm not sure exactly what the "57" represents, but I think at least
part of it specifies the phosphor -- which, I believe, is a longer
persistence type. Note the blue color.

David

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

Question: Why does his scope say "Type 532-57"? My 532 just says "Type
532"... ?


On 04/10/2013 03:30 PM, Steve wrote:

--- In TekScopes@...
<mailto:TekScopes%40yahoogroups.com>
<mailto:TekScopes%40yahoogroups.com>,
David Sligar <d.sligar@> wrote:

Hello, Group --

As possibly many new members do, my first post is a plea for help.
Once my very nice 532 is working again, I might decide that I prefer
"reliable" to "elegant" -- and trade this one in for something a
little newer.


I've been using this scope on a daily basis for about a month. On
Friday morning I tuned it on and suddenly -- no sweep. I've been
going through the beast as carefully
as I can, looking for the bug.
Tubes all check good, no visible damage / exceptions, "all"
voltages
measure
correctly. I suspect one might need a (working) scope to figure out
where the sweep waveform disappears. I decided I'd try running my
function generator as external sweep -- it worked, so that says at
least
the horiz. amp is OK. I've now spent a couple of days
and I'm not sure I'll be able to find what's wrong.

Amazing how helpless we are without tools! I hope one or more
of you
will be able to suggest where I should look.

Thanks very much,
David Sligar
Grants Pass, OR
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

Join TekScopes@groups.io to automatically receive all group messages.