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Acquisition stopped, doesn't happen. I can go all the way to 2ns/div.

Normal trigger but trigger set to +or- 90v (not triggering), it happens.

Single, doesn't happen, can go all the way to 2ns/div, can even trigger
it (in single) and it doesn't happen. The probe was hooked to the
calibrator for the triggers. Normally doesn't matter if there's a
signal there or not.

Thanks!
Vince.


On 08/31/2020 01:43 PM, Siggi wrote:

Hey Vince,

I have no idea what's going on there, though I'd suggest looking at the
power supplies as a first step.
You can also - perhaps - diagnose this a little ways by playing with
trigger and acquisition settings. My guess would be that a power supply

is

collapsing when the sample clock exceeds some particular rate, though
that's of course just a guess.
Does this still occur when the acquisition is stopped? If not, you can
maybe narrow this down by e.g. going to NORM sweep/trigger mode, and
setting up a trigger that never hits. Does it still happen when

acquisition

is started but no trigger fires? How about under a single-shot

acquisition

in AUTO mode, etc.

Siggi

On Sun, Aug 30, 2020 at 5:37 PM Vince Vielhaber <vev@...> wrote:

I picked up a 2440 on ebay that had the dead nvram battery problem. Got
that fixed up with an external battery. Ran thru the self cal and ext
cal and all seems fine, except when the sweep rate is turned above 100
or 200 ns.

In trying to research this a bit, the only thing I could find was on one
of the Tek forums back in 2017 but there were zero responses. Here is
how the other person described the problem:

---------------------------------------------------------------------
The 5 volt regulated rail is getting crowbared when the scope Sec/Div is
set to 100ns or faster. If save is pressed at a slower setting the
Sec/Div can then be set to any value without the 5 Volt rail getting
pulled down. It appears the issue only occurs during an active
acquisition cycle at 100ns Sec/Div or faster.
----------------------------------------------------------------------

While I didn't measure the 5v rail, the screen shrinks a couple of times
as the waveform changes, the inputs get switched to GND and the display
goes blank. Sometimes, if I'm quick enough, I can turn the sweep back
down (1us or slower) and it'll recover, but I still have to go to the
input coupling and switch the inputs off of GND.

Anyone seen this or have any ideas what's going on?

Thanks!
Vince.
--
K8ZW

--
K8ZW

Hey Vince,

My bet would be that if you go back to the 5VD supply, you'll find that
C455 and/or C262 are shot. CR354 is also a suspect, but the bulk caps on
the 5VD supply are the primaries. If you can find a way to look at the
supply before L256, I betcha you're going to find it all jaggy and
disgusting.
If you have a way to measure the two capacitors, that'd work too. Assuming
F269 is not soldered in, you can pretty much isolate the two capacitors by
popping it out.

Good luck,
Siggi

On Mon, Aug 31, 2020 at 6:23 PM Vince Vielhaber <vev@...> wrote:

Yep, I have a 2430A and a couple of 11402s. I used the 2430A.

I checked the + and -5 and the + and -15 volt rails. Sure enough, the
+5 volt rail drops exactly 1 volt while it's happening.

I'm thinking, would piggybacking another 5 volt source on that rail
isolate if it's the power supply or something else?

Thanks!
Vince.


On 08/31/2020 05:09 PM, Siggi wrote:

On Mon, Aug 31, 2020 at 2:04 PM Vince Vielhaber <vev@...> wrote:

Acquisition stopped, doesn't happen. I can go all the way to 2ns/div.

Normal trigger but trigger set to +or- 90v (not triggering), it happens.

Single, doesn't happen, can go all the way to 2ns/div, can even trigger
it (in single) and it doesn't happen. The probe was hooked to the
calibrator for the triggers. Normally doesn't matter if there's a
signal there or not.

Interesting. I'd look at the power supplies, should be easy enough to see
what's happening as this is reproducible. Do you have a second digital or
storage scope to look at what's happening on the power rails?
The only difference between single shot and run without trigger is that

the

single shot capture has a very limited duration. Maybe the problem is

that

a power rail is marginal, and so gets dragged down when the CCDs &

capture

clock keep running for a while.
Once you start capturing the CCDs start storing (and discarding) the
signal, waiting for a trigger.

--
K8ZW

Yep, I have a 2430A and a couple of 11402s. I used the 2430A.

I checked the + and -5 and the + and -15 volt rails. Sure enough, the
+5 volt rail drops exactly 1 volt while it's happening.

I'm thinking, would piggybacking another 5 volt source on that rail
isolate if it's the power supply or something else?

Thanks!
Vince.


On 08/31/2020 05:09 PM, Siggi wrote:

On Mon, Aug 31, 2020 at 2:04 PM Vince Vielhaber <vev@...> wrote:

Acquisition stopped, doesn't happen. I can go all the way to 2ns/div.

Normal trigger but trigger set to +or- 90v (not triggering), it happens.

Single, doesn't happen, can go all the way to 2ns/div, can even trigger
it (in single) and it doesn't happen. The probe was hooked to the
calibrator for the triggers. Normally doesn't matter if there's a
signal there or not.

Interesting. I'd look at the power supplies, should be easy enough to see
what's happening as this is reproducible. Do you have a second digital or
storage scope to look at what's happening on the power rails?
The only difference between single shot and run without trigger is that

the

single shot capture has a very limited duration. Maybe the problem is

that

a power rail is marginal, and so gets dragged down when the CCDs &

capture

clock keep running for a while.
Once you start capturing the CCDs start storing (and discarding) the
signal, waiting for a trigger.

--
K8ZW

On Mon, Aug 31, 2020 at 2:04 PM Vince Vielhaber <vev@...> wrote:

Acquisition stopped, doesn't happen. I can go all the way to 2ns/div.

Normal trigger but trigger set to +or- 90v (not triggering), it happens.

Single, doesn't happen, can go all the way to 2ns/div, can even trigger
it (in single) and it doesn't happen. The probe was hooked to the
calibrator for the triggers. Normally doesn't matter if there's a
signal there or not.

Interesting. I'd look at the power supplies, should be easy enough to see
what's happening as this is reproducible. Do you have a second digital or
storage scope to look at what's happening on the power rails?
The only difference between single shot and run without trigger is that the
single shot capture has a very limited duration. Maybe the problem is that
a power rail is marginal, and so gets dragged down when the CCDs & capture
clock keep running for a while.
Once you start capturing the CCDs start storing (and discarding) the
signal, waiting for a trigger.

In the world of modeling and slot cars (and any other place styrene is
used) there is a repair technique whereby one uses liquid styrene modeling
solvent to "melt" scrap plastic into a goo that can be applied as a filler
to holes, missing sections, or even build up new features that didn't
previously exist. Once the solvent outgasses, the new plastic can be
worked the same as the original. Slot car folks do this all the time,
because kids were encouraged to "modify" their cars, leaving endless cut
wheel wells in their wake. A really good repair is almost invisible, but
usually given away by dirt/slight discoloring in the repair.
Last night I was wondering if the same technique could be applied to all
those broken corners on the TM500 plugins. The plastic isn't styrene, and
while the styrene solvent did dissolve the plastic, it became chalky and
unusable, even the next morning.
Has anyone experimented with this before? Know what type of plastic was
used? It wouldn't be good for large missing sections (too much time
involved), but smaller missing sections could easily be repaired if the
right solvent was found.
-Dave