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Thank you. The papers published in Applied Optics appear to be behind a
firewall. But I see that the first paper is co-authored by Jay Pasaschoff
whose textbooks on astronomy we hsed in college.

DaveD
KC0WJN


On Sat, May 17, 2025 at 14:33 garp66 via groups.io <Bean595939=
[email protected]> wrote:

Came across some references & research papers online for the use of the
Tek 7J20 RSS Spectrometer;
.... might be of some interest:
rick

Tek 7J20



doi.org/10.1364/AO.15.002884







7J20 NASA Pg. 75


NBS/NIST
7J20 Laser combustion of metals Pg. 19



RCA 7J20 Pg. 13 ; … 45 (?)


RCA 4532a PD-Vidicon, AN-4623



DTIC 7J20 Pg. 26


**
& many old posts on this Group, ...not necessarily titled accurately

/g/TekScopes/topic/new_topic_outstanding/80215676

etc.

The following photos have been updated in the SC503 and SC504 Volts/Div and Time/Div Knob Shaft ( /g/TekScopes/album?id=302038 ) photo album of the [email protected] group.

* photo-1.jpg ( /g/TekScopes/photofromactivity?id=3917517 )

*By:* Barry Breaux <groupsio@...>

I don't immediately see a File folder for the 7J20 in the Files section.
Does such exist ?
Are copies of the manuals, etc. in there ?

Came across some references & research papers online for the use of the Tek 7J20 RSS Spectrometer;
.... might be of some interest:
rick

Tek 7J20



doi.org/10.1364/AO.15.002884







7J20 NASA Pg. 75


NBS/NIST
7J20 Laser combustion of metals Pg. 19



RCA 7J20 Pg. 13 ; … 45 (?)


RCA 4532a PD-Vidicon, AN-4623


DTIC 7J20 Pg. 26


**
& many old posts on this Group, ...not necessarily titled accurately

/g/TekScopes/topic/new_topic_outstanding/80215676

etc.

On Wed, May 14, 2025 at 02:09 PM, <bob@...> wrote:

I have put the Windows source code out on GitHub under the MIT license

Thanks for the app.
I'm just guessing... I don't have the hardware.
But, it looks to me... and I might be wrong... that the curvebug app just polls the ARM for a data block, after sending a command byte?
Can't we just open the hardware's serial port, block read the right amount of data, from the buffer, and then write that to a file.
Once we have a 'buffer of data,' we can format it, and display it the way we want.



--
Roy Thistle

On Thu, May 15, 2025 at 9:52?PM Jason B via groups.io <sydbowen=
[email protected]> wrote:

Well..... So I took the case off and checked the voltages on J119 and they
are all correct according to the service manual,

Cool, that's good.

but I'm unclear on how exactly you go about checking the peak to peak
ripple and the 2X line frequency ripple.

TBH I'm no expert at gauging ripple - maybe someone with actual old-school
experience can take a look at the photos and pipe in here?
At this stage you want to eliminate major power supply problems and I think
you've done that.

The kicker here though is that the 850 MHz trace that I had been seeing
was GREATLY reduced while I had the case off and had it set up as normal,
as soon as I turned it off and put the case back on it came back same as
before.

That's kind of interesting, but it brings us back to the original question:
is this internal or is it external? To begin answering that question I
think we need to know whether the attenuator is good.
Hence measure the DC resistance of the attenuator across all
relay settings in DC - going from one end to the other you'll hear relays
click at 2 points, signifying 3 different attenuator settings. You want to
measure the DC resistance from the center conductor to GND at all three
settings. Because there can be a leakage current from the preamp out to the
jack, it's best to measure this both ways and take the average (if there's
a difference) between the two measurements.
Also measure the DC resistance of any one range in AC and 50Ohm
respectively.

These attenuators are prone to contact corrosion, which can make them
behave in wonky ways in different settings. While they're quite robust and
the 50Ohm termination is overload protected, it's not impossible that the
attenuator has been abused somehow, blowing e.g. the 50Ohm termination
and/or some of the attenuator stages.
Now, the GND coupling on these is "faked" in that it doesn't actually
couple GND to the preamp. What actually happens is that the attenuator is
set to 50Ohm termination, AC coupling and 100X attenuation. This has the
effect of dividing the input signal by the bleed capacitor (nominally
1MOhm) and the 50Ohm termination, then attenuating the residual signal by
100. Hence it's important to know that all of those things are intact.

Come to think of it, do you get any signal through the attenuator? E.g. if
you hook up a probe to the calibrator, do you see that signal? Does it
behave as expected?

My $0.02 bets that at least in 50mV/DIV and below, you'll find wonky DC
resistance, and you'll find that the 50Ohm termination is absent. The AC
coupling capacitor might also be MIA.

Really impressive work! :-)
I'm in the UK so I'll aim to find similar facility here, though I've only found fabricators who serve industry so far and I think they'll expect orders by the tonne, not a handful.

Well..... So I took the case off and checked the voltages on J119 and they are all correct according to the service manual, but I'm unclear on how exactly you go about checking the peak to peak ripple and the 2X line frequency ripple. I set everything up according to the service manual. I'll add pics to the previous folder so you can look at what I see. I almost think quite a few of these have out of tolerance ripple values, but I'm not sure. The kicker here though is that the 850 MHz trace that I had been seeing was GREATLY reduced while I had the case off and had it set up as normal, as soon as I turned it off and put the case back on it came back same as before.

Will do. Wouldn't be a huge surprise to find bad filter caps, especially if they've never been changed.

On Thu, May 15, 2025 at 9:47?AM Jason B via groups.io <sydbowen=
[email protected]> wrote:

Oh no, NVM that I see that it's one of the hybrids, not a regular IC. I
may try reseating that and see what happens. If you remove that and power
the scope up with it out of circuit will that cause any major issues? If I
can that would tell me if the oscillation is before or after that hybrid I
suppose?

IIRC the attenuators have a soldered connection to the preamps, or I would
suggest switching them to see whether the problem follows an attenuator.
All that being said, you REALLY need to check the power supplies on J119.
There's really no point to diagnosing anything else until the power
supplies have a clean-ish bill of health.

Oh no, NVM that I see that it's one of the hybrids, not a regular IC. I may try reseating that and see what happens. If you remove that and power the scope up with it out of circuit will that cause any major issues? If I can that would tell me if the oscillation is before or after that hybrid I suppose?

That was the same thing I was thinking, now I just have to figure out what.... I wonder if I can take a small loop of wire and put it near the ch 2 preamp components and narrow it down to exactly what part it is if that's what is going on...

Barry,

How do you want me to get you payment?

Mark

?? ----------------------------------.
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?/?????? it's not permanent.????? /
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?????????? | |? | | \? '.
????????? c__; c__;? '-..'>.__

Hey Jason,

From the photos you posted, I can see that:
1. The scope is triggering on the 850Mhz signal, meaning the trigger hybrid
sees it.
2. The signal is *probably* internally generated, as
/g/TekScopes/photo/302469/3916792 shows GND coupling with
the oscillation visible.

From here, in your shoes, I'd do some organized diagnosis, so if you
measure the below and report back, we can perhaps help you try and suss
what's going on.

1. What is the DC resistance of the attenuator in DC coupling?
This should be 1MOhm within 1% or so, but because of potential leakage
currents, you have to measure this both ways (DMM positive on GND then
center contact) and average. Or you can report both measurements.
You have to measure this across multiple V/DIV settings, as the attenuator
may be working right at some, but not all settings. There are two 10X
attenuator stages, so the total attenuation can be 1X, 10X or 100X, and I
think it's probably best to measure all three combos.

2. What is the DC resistance of the attenuator in AC coupling?
This should be infinite, but you can measure it at any one V/DIV setting.

3. What is the DC resistance of the attenuator in 50Ohm coupling?
This should be 50Ohm within 1% or so, you can measure this once at any
V/DIV setting.

These are all important because of the way GND coupling is implemented
(faked) on these scopes, and so these measurements only allow us to
validate whether the attenuator is working OKish.

You also probably want to pop the case off and measure the voltages on
A1J119, because if your power supplies are bad, there really is no point in
speculating about anything else until those are fixed.

My $0.02 is that your CH2 preamp is oscillating for some reason, but that's
just a guess at this point.

Good luck,
Siggi

On Wed, May 14, 2025 at 4:50?PM Jason B via groups.io <sydbowen=
[email protected]> wrote:

Okay I'll try this. I couldn't upload the vid showing me switching through
everything. Idk if any of these pics will help anyone see anything though.
/g/TekScopes/album?id=302469

I have put the Windows source code out on GitHub under the MIT license for public use. It should be fairly easy for some skilled in the art of Linux to get it running on their OS of choice. It's just a simple C program. The ugly part was trying to determine the COM port name that Windows assigns to the CurveBug. Other than that it's a matter of triggering the device to spit out a trace and then to draw the resulting graph. It uses double buffering to draw the graph off screen then swap it onto the screen in a single operation. This link will get you going if you want the challenge.

Okay I'll try this. I couldn't upload the vid showing me switching through everything. Idk if any of these pics will help anyone see anything though. /g/TekScopes/album?id=302469

Barry- those look great!!!!
搁别苍é别

They are pretty rare, particularly ones that fit a 2465x that has the DVM
option. $110 is probably as inexpensive as you will find. That's slightly
more than what I paid many years ago for my cover (but I do have the DVM
option and so expected to pay a bit more). In my mind, it's kind of like
buying the proper 'scope probes for various applications/purposes for use
with a 'scope. And a rigid front panel cover is pretty important if you are
going to transport or ship the 'scope (for calibration, for instance).

There used to be a member of either the TekScopes or TekScopes2 forums who
occasionally would sell 2465x covers.

While not as protective but just as good for keeping dust off of a 'scope,
large clear plastic bags are a temporary alternative. I have collected a
few of those over the years for use on my 7xxx and 5xx scopes.

DaveD
KC0WJN


On Wed, May 14, 2025 at 14:25 KL7AM via groups.io <w7apm=
[email protected]> wrote:

Ebay, Sphere
One on Ebay but not willing to pay a third of what I paid for the scope

----- Original Message -----
From: "Dave Daniel via groups.io" <kc0wjn@...>
To: "TekScopes" <[email protected]>
Sent: Wednesday, May 14, 2025 10:11:43 AM
Subject: Re: [TekScopes] Want Front Cover 2465b

Where have you looked?

DaveD

On 5/14/2025 1:45 PM, KL7AM via groups.io wrote:

Looking for the above

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Ebay, Sphere
One on Ebay but not willing to pay a third of what I paid for the scope

Where have you looked?

DaveD

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