Date   

7L5 Res shaft encoder

Jean-Paul
 

Bonjour a tous:

Working on 7L5 with L3 input module and OPT 25 tracking generator.

FREQ knob has several defective positions, 1k 2k 5kHz : These intermittently fault to 100k, 200k and 500k respectively.

It contains a shaft encoder under the knob housing

As you jiggle the knob you can get them to read properly for a moment.

Obviously a dirty contact inside the encoder.

To access the encoder guts, seems the entire front panel must come off.

1/ Any way to spray contact cleaner inside ? What recommended cleaner to use? How to get it in?

2/ Any easy way to remove the knob /encoder without complete panel removal?


Many thanks!

Jon


Re: Peter Keller CRT Articles and Book. WAS: Reworked Tek' Lit

 

To the many people who have contacted me expressing interest in a copy of
Peter's book:
Out of concern for his privacy I have contacted him via email to see how he
wants to handle this. As soon as I receive a reply from Peter I will let you
know.

In the meantime thank you for your patience.
Dennis Tillman W7pF

-----Original Message-----
From: Dennis Tillman W7pF [mailto:dennis@ridesoft.com]
Sent: Thursday, November 12, 2020 8:01 PM
To: 'TekScopes@groups.io' <TekScopes@groups.io>
Subject: Peter Keller CRT Articles and Book. WAS: Reworked Tek' Lit

Pete Keller is prolific writer about cathode ray tubes and many other kinds
of display technologies.
He published a very detailed book on the subject in 1991 which I highly
recommend. The book title is:
"The Cathode Ray Tube, Technology, History, and Applications", Peter A.
Keller. 320 p.
ISBN 0-9631559-0-3;
TK7871.73.K46;
621.3815'42-DC20

I purchased my copy directly from Peter in Aloha, OR (not far from
Beaverton). That way I was able to meet him and have him autograph it for
me.

Pete will sell you a copy for far less than Amazon and all the other book
sellers who specialize in hard to find books want for it ($75 to $150). I
have Pete's contact information which I can provide to anyone who wants to
buy his book from him directly. I no longer remember what I paid for his
book but it was well worth it. I read it cover to cover.

Contact me OFF-LIST at dennis at ridesoft dot com for his contact info.

Dennis Tillman W7pF




--
Dennis Tillman W7pF
TekScopes Moderator


Re: 7A12 attenuator board clone

Ed Breya
 

Christian, these special materials were needed ONLY for high-Z, wide band, low leakage applications, like the 1megohm front end of a scope. There are lots of options for low-Z environments.

Ed


Re: 7A12 attenuator board clone

Christian
 

Regarding the special attenuator substrate:

I don't believe that polyethersulfone sees very much use these days. I do
a certain amount of microwave PCB design and I can't say that I've ever
even seen it discussed in the modern literature, or listed on a fab
shop's capabilities list. Of course, with enough money some shops will
build you whatever sort of science project you want (not to say that PES
is/was a science project).

Hook is an effect caused by a change in Er across frequency. Fourier then
says that your microstip (etc) impedance will vary at different locations
in a square wave, and you can end up with some goofy-looking pulses. And
swept signals will have varying amplitudes/losses/etc.

Here in the 2000's, where we're quite enamoured of extreme
digital signalling rates, we have a lot of substrates that are designed
specifically to avoid this problem. As far as I can tell, pretty much
anything better than 'good old FR4' (or its RoHS cousic 370HR) will be fine
for any 'exotic' 7000 time domain plugin use.

I could be wrong, this is not legal advice, YMMV, etc.


Re: 7A12 attenuator board clone

Ed Breya
 

Yes indeed, Raymond - hook was the main thing, and quite obvious. I don't recall if it was due to a non-linear capacitance effect, or a form of dielectric absorption.

Ed


Re: Looking for Tektronix App Note AX-2535

Peter H
 

Don't go via the directory listing please - this is (only part of ...) the internal folder structure of the Wiki.
All the files are listed in the Wiki (e.g. http://w140.com/tekwiki/wiki/Special:NewFiles) and most are referenced from the relevant page with further information.


Re: 7A12 attenuator board clone

 

On Fri, Nov 13, 2020 at 06:44 PM, Ed Breya wrote:


I believe Tek used polysulfone for all high speed, high-Z attenuator boards.
ISTR that a few years ago, David Hess explained in this group that one reason to use the material in this kind of product was to avoid an effect called "hook".

Raymond


Re: 7A12 attenuator board clone

Ed Breya
 

I should mention that for lower cost, Tek used an alternative material for the 2200 series attenuator board assemblies. As I recall, it's a special type made by Oak (Industries?), that works well enough for 100 MHz-class high-Z.circuits, and is mechanically strong enough for "regular" type board applications. There may be other modern types that would do the job.

Ed


Re: 7A12 attenuator board clone

Ed Breya
 

Don't bother cloning, unless you can get the right board material. I believe Tek used polysulfone for all high speed, high-Z attenuator boards. You'll also see it used in microwave stripline components, and probably HP scopes, for good RF performance. It's also good for low leakage - I have a polysulfone (I think) board saved from a junked HP3490A DMM. It's kind of a dark orange/translucent color, used to mount all the high-Z input and auto-zero circuitry directly, without using PTFE standoffs. It's also used for high-Z insulators and switches. After you see it often enough, you kind of recognize the color range, texture, and opacity, and automatically identify it. It's quite fragile, and expensive, so only used where necessary.

BTW I think the reason it's mechanically weak for board use, is that it's in fairly pure form - no reinforcing fibers or fillers allowed, which would spoil the dielectric characteristics that make it a choice in the first place. It's probably comparable to other plastics in mechanical characteristics. I have some 1/4" plates of it, that came from some big old directional couplers. One thing that seems very different is if you clink them together, they sound "glassy" rather than "plasticy," so they are somewhat hard and brittle.

Coincidentally, I just mentioned it in a recent thread here:
https://groups.io/g/TekScopes/message/172980

Ed


Re: Question, and shameless plug...

Ke-Fong Lin
 

Hi John,

No, import taxes are extra and are displayed separately.
However, GSP doesn't charge service fee (UPS or Fedex charges something like 20 euros for that!).
So all in all, I would rate GSP as "very good".

Best regards,


Re: 7A12 attenuator board clone

 

Hi Martin,
I admire your passion. Now that I am retired I have all the time in the world to pursue quirky things that catch my attention regardless of how practical they may be.

I hope you succeed in improving your 7A12. That plugin brings back fond memories for me because it was the very first one I ever used when I was given a loaner 7603 for a weekend.
I have many 7A12s sitting in a box somewhere so I will be happy to send you a few to use for spare parts.

By now (50 years later) I know all those pushbuttons and relays are a nightmare to maintain. And, although I never thought about it at the time, this plugin was a nightmare to build. The side by side arrangement of the two channels meant that each channel's PC Board was a mirror copy of the other one. This made it annoying, to say the least, to produce this plugin.

There were many within Tek who felt the side by side layout of the 7A12 front panel made perfect sense. When Tom Rousseau proposed a much more practical layout for Tek dual trace plugins he was met with a lot of resistance. But there were so many advantages to Tom's proposal that it eventually won out. In the end Tom's 7A26, 7A24, and 7A18A designs were hugely successful.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Martin Hodge
Sent: Friday, November 13, 2020 7:41 AM
To: TekScopes@groups.io
Subject: [TekScopes] 7A12 attenuator board clone

Last year I was lucky enough to find a Tek 7704A scope on CL for free! The scope came with 7A12 and 7B523A plugins. Wanting a 4 channel scope I found another 7A12 on eBay but it turned out to have a broken attenuator board on channel 1. These boards are made of some kind of transparent, rock-candy-like material and are extremely brittle. This one had cracked and separated several traces. I jumped the traces with thin wire and got the board working again. The traces were to two of the relay magnets, no signals running through them. But in the process of unplugging and re plugging the board, one of the connector mezzanines crumbled into several pieces. Something came over me at this point and I decided to waste a lot of time building a new board using modern FR4 process. The photo album linked below shows the process. I was going to make another for channel 2 out of Robertson material and run a comparison with FR4, but before I even priced a board at pcbway I realized I didn't have a signal source with a rise time fast enough to test with. In the end I grew to dislike the 7A12 for it's overly complicated internals, sticky buttons, and meek performance and got rid of them. Though I did like the front panel layout.

https://groups.io/g/TekScopes/album?id=256606
(Be sure to read the photo descriptions for more info)







--
Dennis Tillman W7pF
TekScopes Moderator


Re: Question, and shameless plug...

 

Hi,
The eBay GSP shipping price probably includes local import duty and taxes.

Regards,
John


Re: Reworked Tek' Lit

Bill Perkins <sales@...>
 

Hi Bill,
Thanks for posting these. The reworks look really good.
At my end the link to The Cathode-ray Tube Document is not working however.
Cheers,
Tom
Dennis Tillman advised that the book is still available from its author Pete Keller so even though I found the copy I upped to my site here:

https://archive.org/details/keller1991cathode-ray/page/n1/mode/2up

it seemed that maybe I shouldn't make it available. A grey area I realize, but as I said earlier I don't to bruise anyone's sensibilities.

Bill


Re: Interesting scope on eBay. Hickok copy of 535 or Tektronix?

Leon Robinson
 

When I had the Jettronic 535 clone I found several places where they had changed the circuit, because it didn't match the 535 manual.  I got it to work but never quite right.

The Lavoie worked until ok until I got a 545.


Leon Robinson  K5JLR

-------- Original message --------
From: ken chalfant <kpchalfant@msn.com>
Date: 11/12/2020 11:41 PM (GMT-06:00)
To: TekScopes@groups.io
Subject: Re: [TekScopes] Interesting scope on eBay. Hickok copy of 535 or Tektronix?

Greetings,

Following is the really short version of the story I learned.

At some point the military was compelled to go out for competitive bids on “Tektronix” oscilloscopes.

Tek may have been “compelled” to share technical information for the bid process.

Regardless of the details both Hickok and Lavoie made Tektronix knock-offs.  Perhaps other companies did as well - that I don’t know.

As I recall the “equivalent” scopes were not all that equivalent.  At least some lacked the ceramic parts strips using conventional terminal strips and compromised on other components.

If you come across one and bring it to life it will probably be a reasonable scope for its generation, but it will be somehow less than a Tek scope.

Hopefully others will add to, or accurize, what I have offered in this message.

Regards,

Ken


On 12Nov, 2020, at 9:15 PM, Leon Robinson <leon-robinson@sbcglobal.net> wrote:

I had a Jetronic about 50 years ago.
I have a LA-265 in the storage shed if it wasn't destroyed when the roof blew off 2 or 3 years ago.


Leon Robinson  K5JLR

-------- Original message --------
From: Jim Tibbits <ab7vf1@gmail.com>
Date: 11/12/2020  9:21 PM  (GMT-06:00)
To: TekScopes@groups.io
Subject: Re: [TekScopes] Interesting scope on eBay. Hickok copy of 535 or Tektronix?

Looks similar to tek 545 ...likely DOD contract to Hickok similar to one
given by them to Lavoie LA-265...
Jim


On Thu, Nov 12, 2020 at 2:33 PM John Williams <books4you4@mail.com> wrote:

Here is something interesting on the eBay site:


https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.ebay.com%2Fitm%2FVintage-Tektronix-Oscilloscope-MX-2330-G%2F193747752801%3Fhash%3Ditem2d1c441761%3Ag%3AcIYAAOSwcbpfrZ9u&;data=04%7C01%7C%7Cbea90295bde04e142de408d8878ad163%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637408377566465985%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=aJeHGnZiVIIxMApTXBvyh8pphRDqzhuiIDr8bI%2BDCUo%3D&amp;reserved=0

It looks identical to a Tektronix 535 but has Hickok nameplates. I would
be very interested in the story behind this. I wonder if it is a Tek scope
they used for a prototype, or something that they actually constructed.
Anyone have any ideas? Thanks.














Re: Peter Keller CRT Articles and Book. WAS: Reworked Tek' Lit

Colin Herbert
 

Just for information, this book is available for download at:
https://archive.org/details/keller1991cathode-ray/page/n1/mode/2up
It is open-source and thus free to download. Whether this suggests that
clean-up and re-posting is acceptable, I don't know.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dennis
Tillman W7pF
Sent: 13 November 2020 04:01
To: TekScopes@groups.io
Subject: [TekScopes] Peter Keller CRT Articles and Book. WAS: Reworked Tek'
Lit

Pete Keller is prolific writer about cathode ray tubes and many other kinds
of display technologies.
He published a very detailed book on the subject in 1991 which I highly
recommend. The book title is:
"The Cathode Ray Tube, Technology, History, and Applications", Peter A.
Keller. 320 p.
ISBN 0-9631559-0-3;
TK7871.73.K46;
621.3815'42-DC20

I purchased my copy directly from Peter in Aloha, OR (not far from
Beaverton). That way I was able to meet him and have him autograph it for
me.

Pete will sell you a copy for far less than Amazon and all the other book
sellers who specialize in hard to find books want for it ($75 to $150). I
have Pete's contact information which I can provide to anyone who wants to
buy his book from him directly. I no longer remember what I paid for his
book but it was well worth it. I read it cover to cover.

Contact me OFF-LIST at dennis at ridesoft dot com for his contact info.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Glydeck
via groups.io
Sent: Thursday, November 12, 2020 10:53 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] [Test-Equipment-For-Sale-Wanted-or-Exchange]
Reworked Tek' Lit

Bill,

Really nice scans. Thank you for sharing.

George
On Nov 12, 2020, at 8:39 AM, Bill Perkins <sales@pearl-hifi.com> wrote:

Guys:
Here's a bunch of Tek' lit I've lately reworked, noting that I've
posted this to several lists.

The Cathode-ray Tube, 330pgs:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/
Tektronix_Lit/The_Cathode_Ray_Tube.pdf

Tek CRT History:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/
Tektronix_Lit/Textronix_CRT_History.pdf

Tek_7K_Series_Digital_Plug-In_Applications:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/
Tektronix_Lit/Tek_7K_Series_Digital_Plug-In_Applications.pdf

A_Primer_of_Waveforms_and_Their_Oscilloscope_Displays:
https://www.pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/35_Tektronix/
Tektronix_Lit/A_Primer_of_Waveforms_and_Their_Oscilloscope_Displays.pdf

Best,
Bill Perkins











--
Dennis Tillman W7pF
TekScopes Moderator


7A12 attenuator board clone

Martin Hodge
 

Last year I was lucky enough to find a Tek 7704A scope on CL for free! The scope came with 7A12 and 7B523A plugins. Wanting a 4 channel scope I found another 7A12 on eBay but it turned out to have a broken attenuator board on channel 1. These boards are made of some kind of transparent, rock-candy-like material and are extremely brittle. This one had cracked and separated several traces. I jumped the traces with thin wire and got the board working again. The traces were to two of the relay magnets, no signals running through them. But in the process of unplugging and re plugging the board, one of the connector mezzanines crumbled into several pieces. Something came over me at this point and I decided to waste a lot of time building a new board using modern FR4 process. The photo album linked below shows the process. I was going to make another for channel 2 out of Robertson material and run a comparison with FR4, but before I even priced a board at pcbway I realized I didn't have a signal source with a rise time fast enough to test with. In the end I grew to dislike the 7A12 for it's overly complicated internals, sticky buttons, and meek performance and got rid of them. Though I did like the front panel layout.

https://groups.io/g/TekScopes/album?id=256606
(Be sure to read the photo descriptions for more info)


Re: Another A5 board repair attemp - help needed

Siggi
 

On Fri, Nov 13, 2020 at 7:49 AM Rogerio O <rodd414@gmail.com> wrote:

Hi Siggi,
Although it seems it is not here were the problem is, I would like to
learn how to do it properly, so I posted this reply.
I have tackled a wire to pin19 of the DAC and hooked a P6109B to it - this
is CH1 of the scope
Than I am using a P6133 to probe the output pin of both MUXES, on CH2.
The two are 10X probes, right?
Yups.


The scope is a TDS2024B.
I could manage to adjust the trigger to view part of a complex signal with
about 2.5Vpp.
What I can't understand is that NONE of the signals present at the MUXES
outlets seems to vary with time and their voltages never get higher than
120mV.
Why is that?
I can't explain that, except perhaps you're not looking at the right part
of the DAC's output. The DAC is used for other purposes than just
refreshing the S&H analog voltages, notably it does potentiometer scanning.
Also note that the analog voltages only change with control or setting
changes on the scope. Droop aside, they should be pretty much a flat DC
level otherwise. Have you tried twiddling the front-panel controls while
looking at the MUX outputs? Maybe if you e.g. track down the A TRIG LVL
output on the MUX, then twiddle the trigger level control while you look at
the output. What you should see is a portion of the DAC output signal will
change with the pot, and you should see the MUX output track with those
changes.

What do you see if you flip this around and trigger on one of the MUX
outputs while you twiddle the controls?

I remember looking at this on the A5 board of my 2467, and I remember
seeing the probe visibly loading the holding capacitor, at least on some of
the outputs. I seem to remember the various outputs are refreshed
at different rates also, so some may droop more than others. I don't
remember the magnitude of the effect, though, it's been years since I did
this.
If you look at the PCB traces around the MUXes and op-amps (TL074s?),
you'll see that there are "guard traces" from the output of each op-amp,
encircling each MUX output and the S&H components. This is to minimize
leakage across the PCB (or say, due to dirt on the PCB), e.g. these are
high impedance points.

Have fun!
Siggi


Re: Reworked Tek' Lit

Tom Phillips
 

Hi Bill,
Thanks for posting these. The reworks look really good.
At my end the link to The Cathode-ray Tube Document is not working however.
Cheers,
Tom


Re: Another A5 board repair attemp - help needed

Rogerio O
 

Hi Siigi.

"
I did the math and I'm 90% certain that your R2015 is not connected to pin
14 of U2101"

---Using a DMM I could confirm that one end of R2015 is indeed connected to pin14 of DAC and it measures 11.74K.

The parts that I ordered from Mouser will arrive today and I will desolder R2015 and replace this resistor anyway.

A am trying to minimize desoldering operations in order to minimize the risks of damaging the board.


Re: 067-0525-01 or equivalent needed.

Jean-Paul
 

We use a good quality BNC T and a pair of Tektronix precision 50 ohm 0.5 m cables, the type specific to SG503.

A 2-10X wideband passif attenuator like Mini Circuits HAT series can reduce abberations due to VSWR and reflection.

Jon

9441 - 9460 of 182448