On 4/19/20 4:09 PM, Bill Perkins wrote:
????TRYING to d'load:

????App Note 123 - Floating Measurements and Guarding

from here:

????https://www.keysight.com/main/editorial.jspx?ckey=1127547&id=1127547&lc=eng&cc=CA


I get the attached screen shot ?

????Furthering Keysight's endless teases these days one can pull down
from that same page the attached spreadsheet, promising much more info
but w/o a single working link.

????Do they have a bunch 20-somethings chugging Red Bull doing this
stuff anymore ?

  I expect it's more legions of dramatically underpaid (but willing)
people in India.

  File sent off-list.

          -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA
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Well written application notes are some of the best educational tools available; whether they are instrument specific or more general.
I prize the General Radio, Boonton, Wiltron and Hewlett Packard app notes. They have been a source of a great deal of my practical education.
Stuart K6YAZ
Los Angeles, USA

On 4/19/20 9:07 PM, Jared Cabot via groups.io wrote:

I have a 6644A, which is a little different, that I added front panel binding posts to. I 3D printed a holder that sits inside to position the binding posts correctly.
I also added a switch to select between internal sense connection or the external sense binding posts.


As for shorting links, I usually use these ones:

Standard binding-post spacing is exactly 3/4 inch.

--doug

? Stay OFF the Danaher 57x series. My replacement for these is almost ready.

As for the 53310A: not sure if it pays. You would need to use an FPGA to harvest the digital data being farted out. I wanted to do it once, but never had the time. However, afaik, the video board on these units is a separate board (as per the late Jzon Geller), and some instructions in the service manual of the 53310A even give some data about the pinout.

Tam

---

With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 14k other followers by visiting the Crazy Electronics Lab at

Am 16. April 2020 19:56:40 MESZ schrieb Bill E <solartron@...>:

That's something I've been thinking about for a while now. I have several instruments where I'd like to replace the CRT. I know there have been a few people in the past that have done some for specific instruments, but I don't know of a general solution. One would think that for many instruments, should be fairly easy. They usually used OEM CRT displays that had simple analog or pseudo-digital intensity signals, and standard or close-to-standard scan rates. But, for the older style oscopes where it was a classic deflection CRT with the text additions being done by vector graphics, whole different game.My 54540 really needs a new CRT, modern replacement would rock. I'll add it to my list. :)

16 apr. 2020 kl. 2:04 em skrev Tam Hanna <tamhan@...>:

? Stay OFF the Danaher 57x series. My replacement for these is almost ready.

As for the 53310A: not sure if it pays. You would need to use an FPGA to harvest the digital data being farted out. I wanted to do it once, but never had the time. However, afaik, the video board on these units is a separate board (as per the late Jzon Geller), and some instructions in the service manual of the 53310A even give some data about the pinout.

Tam

---

With best regards
Tam HANNA (emailing on a BlackBerry PRIV)

Enjoy electronics? Join 14k other followers by visiting the Crazy Electronics Lab at

Am 16. April 2020 19:56:40 MESZ schrieb Bill E <solartron@...>:

That's something I've been thinking about for a while now. I have several instruments where I'd like to replace the CRT. I know there have been a few people in the past that have done some for specific instruments, but I don't know of a general solution. One would think that for many instruments, should be fairly easy. They usually used OEM CRT displays that had simple analog or pseudo-digital intensity signals, and standard or close-to-standard scan rates. But, for the older style oscopes where it was a classic deflection CRT with the text additions being done by vector graphics, whole different game.My 54540 really needs a new CRT, modern replacement would rock. I'll add it to my list. :)

From: "David Platt" <dplatt-groups@...>
To: [email protected]
Sent: Saturday, April 18, 2020 10:52:18 PM
Subject: Re: [HP-Agilent-Keysight-equipment] HP 652A Dial Calibration

I agree, it's not a good idea to start bending plates on that big three-way
air variable capacitor.? Once done there's really no way to go back, and I
suspect you'd be likely to make things worse rather than better.

The HP 651 has a complex frequency-calibration procedure in the service
manual.? Adjusting the calibration on some bands requires changing out a
pair of selected-at-manufacture-time resistors on the bandswitch.? For some
other band there's an adjustment capacitor.? I believe that the 652 has the
same architecture, and I'd recommend following the manual instructions
carefully if you decide to do this.

One thing it would probably be good to do first... measure, record, and plot
the actual frequencies on each of the bands at each major digit position.
? By comparing the bands you may be able to see whether there's an overall
shift in the calibration affecting most or all of the bands (which would
point to a dial-positioning or main-capacitor issue) or whether some bands
are shifted differently than others (which might suggest that the
band-specific resistors or caps are out of whack).

The 651B is only spec'ed to 2% frequency accuracy on some bands and 3% on
others, so exact dial calibration can't really be expected.

Oh... make sure that you take your measurements with the cabinet lid and base
on and the screws tightened, as the manual advises.? There's a very
significant frequency and calibration shift if you take off the lid... the
parasitic capacitance from the active circuit to the case is part of the
equation!

Also, check the tuning cap for contamination (dust, etc.) - if there's any
present it could throw things off.? I bought a 651 which was quite balky and
wouldn't oscillate at all in some portions of the dial range (on any band).
? I found some dark gunk on the plates, and splashed in a few places around
the base of the capacitor... looked as if somebody had spattered Coca Cola
on it.? It took a good, careful water-wash to get it out (and then a spritz
with contact cleaner to flush out the water, and some blown air to dry it
properly) and now it oscillates and tracks nicely.? (It also had the "HP
grease turns to cement with age" problem, and I had to do a
strip-down/clean/lubricate much as you did.)

If I ever get my hands around the neck of either of these men, they
will have a difficult day.
-Dave