Re: Strange Tek2440 issue

Vince Vielhaber

F269 is soldered but I was able to clip onto L256. A minor amount of ripple that only changed by a few millivolts when I added a 2200uf cap across it. No change when I switch below 200ns.

The 5V jumping around is the 5V regulated that C494 is on. There it drops a volt or so when I switch below 200ns. According to my Fluke, when it goes out completely it holds at 3.93v.

The 10v reference that divided and sent to U870B is solid.


On 08/31/2020 06:43 PM, Siggi wrote:
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
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,

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?


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
single shot capture has a very limited duration. Maybe the problem is
a power rail is marginal, and so gets dragged down when the CCDs &
clock keep running for a while.
Once you start capturing the CCDs start storing (and discarding) the
signal, waiting for a trigger.


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