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I've tried cleaning U500 and U900 to no avail, and then I swapped U900 and
U700 again to no avail. Will continue searching for sweeps that might work
and looking at that opamp.

On Tue, Mar 19, 2019 at 01:15 PM, Siggi wrote:

On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to

run

the B sweep, but it isn’t running.

I would start by pulling, cleaning and re-seating U900. Second perhaps

swap

U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the

constant

current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.

On Tue, Mar 19, 2019 at 8:54 AM <thespin@...> wrote:

It’s not. The proper lights come on suggesting the scope is trying to run
the B sweep, but it isn’t running.

I would start by pulling, cleaning and re-seating U900. Second perhaps swap
U900 and U700.
If that doesn't help, you might be able to narrow this down a bit by
experimenting with various A/B sweep speed combos and B delay/trigger
settings. If there's any combo that will produce a sweep, then you can
start eliminating problems.
If there's no combo that'll start the sweep, then I'd focus on the constant
current generator op-amp (U910A in my 2467 schematic), and then on the
delay ref outputs from the A5 board.

Hi, Reg.

Regarding fast pulses and such, there is a wealth of information at Jim
Andrews' page here: He founded
Picosecond Pulse Labs in 1980 and sold it to Tektronix in 2014. I used
PPL products with a CSA803 back in the mid 1990's at Lockheed. I think
the sampling head I used was an SD-24, but since it was about 25 years
ago, my memory is a bit fuzzy.

These days I have a 7904, a 7603, a 7S12, a 7S11, two S-4 sampling
heads, S-53 and S-51 triggering heads, etc in my garage lab. Oh, and a
couple of 10:1 probes I made out of board-edge SMA connectors, 450 ohm
(470 paralleled with 1.8k ohm) 0402 resistors, and 3-pin right-angle 0.1
inch spacing headers. I've not completely characterized the probes, but
at least they pass up to about 12-13 GHz without much attenuation above
the expected 20 dB. Planning to use them to probe some digital RF
boards I'm going to build for work (Raytheon). Too much trouble to try
to get a fast enough sampling scope at work :(

Enjoy the PPL app notes! I've referred to AN-2a through -2e often.

Thanks for the literature references. I'll have to check them out
(someday).

Jim Ford


------ Original Message ------
From: "Reginald Beardsley via Groups.Io" <pulaskite@...>
To: [email protected]
Sent: 3/14/2019 6:03:56 PM
Subject: Re: [TekScopes] Test input for an SD-32 sampling head

I have one of Leo's 100 pS impulse units as a source for initial

experiments. If I can narrow that to 10 -20 pS with discrete SMD parts I
may be able to get the idea to work. There's a close connection to the
Hilbert operator hiding in there somewhere.

I've been reading an excellent book on FPGA implementation of DSP by

Roger Woods et al most of the afternoon. So I've not started on the
dissertation yet. I can't really say much else until I understand the
mathematics and physics of using the reverse biased diodes as capacitors.
That should keep me entertained for a few weeks at least.

In any case, failure doesn't matter. It's a hobby project, not a client

deliverable. I've been fascinated by the problem of getting a fast rise
time edge for a long time. It's a bit of circular logic. My excuse for
doing it is I bought an 11801 and my excuse for buying the 11801 is so I
could try to do it. If I can narrow the 100 pS pulse by 5x I'll have an
excuse to buy an SD-32.

I spent 3 years studying sparse L1 pursuits using "A Mathematical

Introduction to Compressive Sensing" by Foucart and Rauhut as a text
followed by reading the original papers by Donoho, Candes et al. Beats the
hell out of watching television. I just wish I could find someone else who
was interested in the subject to discuss it with. It's quite amazing what
you can do with sparse L1 pursuits and really easy to do in practice.
Understanding the math is not easy, but most people use FFTs without really
understanding them.

Have Fun!
Reg

---
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Is it possible the switch isn't operating when you pull the knob out?? There
is a plastic piece between the knob and the switch that can be broken.

Hey All,

I've managed to find some time to play with my 2467B and have been trying to
untangle whether the non-working CTT option (CT TEST 86 FAIL 02) has broken
the B sweep or if the B sweep itself isn't working at all. Regardless of
whether B "RUN AFT DLY" "TRIG AFT DLY" or "TRIG Delta DELAY" is selected, I
see "MISSING B TRIG" on screen. I reckon "TRIG AFT DLY" shouldn't work at all
since this is what's indicated isn't working by TEST 86 FAIL 02.

So here's what I observe. I get a stable trace using the A sweep. I pull the
SEC/DIV knob, turn it one click to the right, and push it back in to switch to
the B sweep. I then observe no trace at all, for any position of the holdoff
knob, for any value of the DLY value on screen, and for any B trigger setting.
This scope is pretty complex and I understand I might just not be using the B
sweep correctly... but if indeed this is abnormal behavior, how can I tell if
the CTT failure is causing this, or if it's something related to the A/B
trigger hybrid, B sweep hybrid, or display sequencer IC? Or perhaps something
totally unrelated? Does anyone have any experience with this behavior?

from Tim P (UK)
I have three 5000-series storage 'scopes where the store mode seems weak
and lacking 'bite' . I have done the 'fade positive' thing as recommended
in the manual, to clean out the dead ions (!), and been through the storage
setup, and it all works sort-of-OK, in that it stores and erases as it
should, but the stored trace / background has little contrast, and
increasing Intensity range just blooms the CRT. Is the CRT showing its age
? Affects all three instruments to different degree.
many thanks
Tim