Date   

Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Hi Federico,
I see, a sound card at 1 Hz is probably not the most ideal signal source!
Don't you have another scope to check power supplies for ripple and correct values? That's more attractive than adding or changing capacitors "in the wild".
In non-store mode your 1 kHz square wave was correct but the readout showed 2 s/div. But the timing switches at diagram <5> and the outputs of U780 do not determine the X10 multiplier. This suggests a fault in common, could be like you say a power line.
Albert

On Wed, Jun 2, 2021 at 10:59 AM, Pitpat wrote:


Hi Albert!
In reality I kinda expected to have some sorta of 50hz noise since I had to
use a tone generated by a PC soundcard.
I guessed that with such low frequencies audio signal might have all kind of
artefacts.
Also the signal passed through a cheap jack and an alligator-clip to BNC
probe, so yes not the cleanest setup.
You gave an idea though, could the problem be related to some sorta of ripple
current trough the -8,6 rail? Should I try to decouple it with a cap.?


Re: practical limits of chopper circuits?

 

cheater cheater,

You're talking about time division multiplexing, and you would need to transmit the multiplexing clock along with the multiplexed data. The best solution to this is probably to send a self-clocking signal. At this point you are looking at significant encoding and decoding of the signal, possibly some kind of time domain structure like an NTSC comosite color TV signal, with a section of the signal set aside to synchronize the sender and receiver clocks. Or you could transmit on multiple frequencies over the same wires, but I don't understand any of the math required to make that sort of thing work.

I agree with Dave Voorhis that this would be much simpler if you just digitized the audio signals and sent them over a data line. Gigabit ethernet is cheap, as are audio DACs, and the processing power needed to handle those audio signals barely moves the needle with modern CPUs.

Of course it's so much cooler to do something like this in the analog domain, so you have my sympathy.

-- Jeff Dutky


Re: practical limits of chopper circuits?

Dave Voorhis
 

I can imagine all manner of problems trying to run 16 analog audio signals over one cable.

But put a good A/D converter at each audio-to-analog transducer -- or as close to it as is feasible -- and you can easily run multiple digital channels over one cable, and get the quality benefits of running almost entirely in digital with minimal points of analog degradation.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of cheater cheater
Sent: 02 June 2021 08:42
To: TekScopes@groups.io
Subject: [TekScopes] practical limits of chopper circuits?

Hi all,
I was recently thinking about how single-gun Tektronix direct-display scopes display multiple traces at once. There's essentially alternating mode, and the other mode that uses a chopper. And that runs at a pretty high frequency. For another application entirely (not tek scope related), I would like to run 16 audio signals over one cable. The obvious option is to run 32 conductors (2x16 for balanced signalling). But given that I'll be looking at ~100 connections, that easily adds up. So I was wondering if it's possible to use a similar in vein chopper arrangement to multiplex, and then demultiplex, the signal? I can easily distribute the clock signal around the whole system using a fixed distribution network, which isn't patchable, and then run the audio via patch cables. What are the limits of such a set up? If you want 16 * 22000 Hz bandwidth, then you'd want to have a total of 352000 Hz bandwidth via the wire... even a normal 1/4" jack will do that over moderate distances (up to 5m). How complex could this circuit turn out to be if I wanted to be able to have very good recovery of DC signals? By this I mean down to 0.002% of the full range which is -15V...15V.

I would appreciate any insights over how feasible this is given the kinds of bandwidths being used with chopper circuits in Tek scopes and other places.

Here's an interesting design for a 1MHz beam chopper.
https://www.researchgate.net/publication/29522240_A_1_MHz_beam_chopper_for_the_KAON_factory

However, it doesn't really go in depth into how the circuit works.

This also is tangential to another question I've had for some time. If I wanted to use a 7k series scope with a lot of low bandwidth traces - say, 8 or 16 audio rate traces - how would one build a chopper circuit for that? I can easily imagine this being possible to realize in a single custom plugin.

I know there are 4-trace plugins for the 5k series, and I assume two could be used in a single mainframe giving you a total of 8 traces.
However, there's no such thing for 7k series.

Thanks


Re: Tek 2230, almost fixed but with a problem out of my competences

Pitpat
 

Hi Albert!
In reality I kinda expected to have some sorta of 50hz noise since I had to use a tone generated by a PC soundcard.
I guessed that with such low frequencies audio signal might have all kind of artefacts.
Also the signal passed through a cheap jack and an alligator-clip to BNC probe, so yes not the cleanest setup.
You gave an idea though, could the problem be related to some sorta of ripple current trough the -8,6 rail? Should I try to decouple it with a cap.?


Re: does anyone have one of the 1960's era Tek Circuit Computers?

 

Hi all,
it might make sense to try one of the "print on demand" houses. The
cost might be a bunch more, but in the end they'll still be
inexpensive, and everyone can request the print on their own, so if
you decide to break the copyright law, that's on you. I know they do
prints on aluminum and on some types of plastic (eg pvc), and it might
be a bit challenging to find something with good enough print
resolution, but I'm fairly sure a good place to print these can be
found.

All the best

On Sun, May 23, 2021 at 9:03 AM John Kolb
<jlkolb@jlkolb.digitalspacemail17.net> wrote:

Thanks for posting the link, I've got one of the metal ones, rather than
the later plastic. Didn't know there was a manual for it. I've found it
useful over the years, though most often use one of the on-line
calculators nowadays.

John

On 5/22/2021 7:00 AM, Doug wrote:
https://w140.com/tekwiki/wiki/File:Tektronix_Circuit_Computer_1961.pdf









practical limits of chopper circuits?

 

Hi all,
I was recently thinking about how single-gun Tektronix direct-display
scopes display multiple traces at once. There's essentially
alternating mode, and the other mode that uses a chopper. And that
runs at a pretty high frequency. For another application entirely (not
tek scope related), I would like to run 16 audio signals over one
cable. The obvious option is to run 32 conductors (2x16 for balanced
signalling). But given that I'll be looking at ~100 connections, that
easily adds up. So I was wondering if it's possible to use a similar
in vein chopper arrangement to multiplex, and then demultiplex, the
signal? I can easily distribute the clock signal around the whole
system using a fixed distribution network, which isn't patchable, and
then run the audio via patch cables. What are the limits of such a set
up? If you want 16 * 22000 Hz bandwidth, then you'd want to have a
total of 352000 Hz bandwidth via the wire... even a normal 1/4" jack
will do that over moderate distances (up to 5m). How complex could
this circuit turn out to be if I wanted to be able to have very good
recovery of DC signals? By this I mean down to 0.002% of the full
range which is -15V...15V.

I would appreciate any insights over how feasible this is given the
kinds of bandwidths being used with chopper circuits in Tek scopes and
other places.

Here's an interesting design for a 1MHz beam chopper.
https://www.researchgate.net/publication/29522240_A_1_MHz_beam_chopper_for_the_KAON_factory

However, it doesn't really go in depth into how the circuit works.

This also is tangential to another question I've had for some time. If
I wanted to use a 7k series scope with a lot of low bandwidth traces -
say, 8 or 16 audio rate traces - how would one build a chopper circuit
for that? I can easily imagine this being possible to realize in a
single custom plugin.

I know there are 4-trace plugins for the 5k series, and I assume two
could be used in a single mainframe giving you a total of 8 traces.
However, there's no such thing for 7k series.

Thanks


Re: Need Detent Ball Bearing for Sweep Mode Switch

Ed Breya
 

So true indeed. After a lifetime of saving stuff, and performing large inventory reductions every so often, I still have a long way to go. My standard defense against mockery of my hoarding behavior and common sense, is that yes, I can't picture possibly ever using even one percent of it - the problem is that I don't know which one percent that is. I've never had any complaints about managing to come up with an obscure part and solution for a need.

Ed


Re: Need Detent Ball Bearing for Sweep Mode Switch

Wayne
 

It seems to be a rule of nature that if you toss anything, even if you have had it for decades, within a couple of weeks you will have a critical use for it. OTOH, if you keep everything before long you won't be able to get around your house without crawling under things

That is so true it's just painful!!


Re: Need Detent Ball Bearing for Sweep Mode Switch

Richard Knoppow
 

It seems to be a rule of nature that if you toss anything, even if you have had it for decades, within a couple of weeks you will have a critical use for it. OTOH, if you keep everything before long you won't be able to get around your house without crawling under things.

On 6/1/2021 6:18 PM, n4buq wrote:
Yeah, I've found a few places but they're 25 or more. Not really that big of a deal and if I don't find one or two, then I'll get a pack. In any case, it beats buying an entire switch. I'm just so disappointed in myself for "cleaning up" and now not having what's missing. I should've known a blank spot for that bearing would turn up eventually.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@gmail.com>
To: TekScopes@groups.io
Sent: Tuesday, June 1, 2021 6:30:34 PM
Subject: Re: [TekScopes] Need Detent Ball Bearing for Sweep Mode Switch

I don’t have a stash of ball bearings (that I know of, but there’s a lot of
stuff of my dad’s, out in the garage, that I haven’t had a chance to go
through, so who knows), but you can get 100 of them for $5 on Amazon.

— Jeff Dutky






--
Richard Knoppow
dickburk@ix.netcom.com
WB6KBL


Re: Need Detent Ball Bearing for Sweep Mode Switch

n4buq
 

Yeah, I've found a few places but they're 25 or more. Not really that big of a deal and if I don't find one or two, then I'll get a pack. In any case, it beats buying an entire switch. I'm just so disappointed in myself for "cleaning up" and now not having what's missing. I should've known a blank spot for that bearing would turn up eventually.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jeff Dutky" <jeff.dutky@gmail.com>
To: TekScopes@groups.io
Sent: Tuesday, June 1, 2021 6:30:34 PM
Subject: Re: [TekScopes] Need Detent Ball Bearing for Sweep Mode Switch

I don’t have a stash of ball bearings (that I know of, but there’s a lot of
stuff of my dad’s, out in the garage, that I haven’t had a chance to go
through, so who knows), but you can get 100 of them for $5 on Amazon.

— Jeff Dutky






Re: Need Detent Ball Bearing for Sweep Mode Switch

 

I don’t have a stash of ball bearings (that I know of, but there’s a lot of stuff of my dad’s, out in the garage, that I haven’t had a chance to go through, so who knows), but you can get 100 of them for $5 on Amazon.

— Jeff Dutky


Need Detent Ball Bearing for Sweep Mode Switch

n4buq
 

Previously I asked about a Trigger Mode Switch for my 453. That should have been the Sweep Mode Switch. Sorry about that.

In any case, I pulled the old one and I think it's repairable; however, it's missing one of the 7/64" ball bearings that are used as the spring detent bearings.

Sadly, for a few years, I kept noticing a tiny ball bearing on the kitchen counter (where I'd sometimes work on test equipment, this 453 included), and, last year during a cleanup, I think I finally tossed it as I had no idea where it went. I usually hang on to things like that but it looks like I didn't this time.

Anyone have a stash of those and would be willing to send one or two to me for a fee? Apparently those are standard sizes as I see them for sale at several places but they're for quantities of 25 or more and I don't want that many tiny ball bearings floating around the shop and I'll likely never need another one.

We have a fairly well-stocked old-fashioned hardware store in town and I'm going to try there but not holding out too much hope and thought I'd ask here.

Thanks,
Barry - N4BUQ


067-0502-01 Calibrator

Stephen
 

Hi all,

My recently acquired 067-0502-01 calibrator is working fine as far as as the amplitude steps go. It is perfectly calibrated too.
However, the duty cycle of the square wave started looking more and more like a negative going pulse.
Now, 2 weeks later, it totally looks like that. The amplitude is perfect, but it’s not a square wave anymore.
It as been completely recapped. Worth mentioning that issue had started before the recap, though. And it has worsened.
As someone suggested to me offline, I looked at D112 and D122, and they seem completely fine and matched. I even put 2 new ultra fast diodes to see what the effect was, and nothing changed. I put the originals back in.
I’ve also checked the components around V155, and everything seems to be ok as well. Could V155 be the cause of that? I know this is not terribly important in this application, but it’s bugging me.

Does anyone have any clue that could guide me in the right direction?

Thanks.


Re: 1503B Backlight

Roy Thistle
 

On Tue, Jun 1, 2021 at 12:40 PM, Harvey White wrote:


They need perhaps 100 or so volts
-- yes! meant to type 300 V, not 3000 V! ... was thinking of the frequency of the inverter 3000 Hz... that is for the badafruit 12 V powered inverter I have... which is 300 V common mode.
The inverters for the wire.. they tend to drive low current (since the wire is low current)... and so the inverters have a high output impedance, and so a high open circuit voltage. (vacuum tube types can ignore the "high voltage" part... and anyway, as I said, they don't bite... the current is too low.)
The inverter open circuit voltage can be 50 V, if you're only driving a small segment... but, longer segments need higher current, so the open circuit voltage can jump to a couple of hundred volts.

--
Roy Thistle


Re: 1503B Backlight

Harvey White
 

CCFLs have striking voltages about 1600 volts or so, and running voltages about 800.

EL panels are essentially transparent capacitors with a phosphor as a dielectric.  They need perhaps 100 or so volts, and the color can be frequency dependent.  You used to be able to take an old audio output transformer, run it backwards, connect the EL panel to the old primary, and see blue or blue/green in time with the music.

Harvey

On 6/1/2021 1:28 PM, Roy Thistle wrote:
On Tue, Jun 1, 2021 at 09:55 AM, Jeff Dutky wrote:

Just search for "electroluminescent sheet"
or... tape, foil, wire... as well... on aliblaba, alinexpress, and badafruit.
3 V and 12V powered inverters also available.... again on all those places.
It's easy to work with, and low power... so even though it's high voltage (3000 V), it's safe to touch and wear (as many an arteest does, around the city, on a dark night.)
Downsides are it is fragile... or at least not butterfinger proof... and it isn't easy (not impossible) to dim... and low lumen.
The electroluminescent green wire would be great for pimping out those orange painted 500s I read about.

Roy Thistle





Re: WTB or Repair Tek RSA3308A Front Panel PCB. Mine is Dead

Roy Thistle
 

On Mon, May 31, 2021 at 08:53 PM, Dave K7DMK wrote:


Any suggestions regarding additional troubleshooting
Take the label off the keyboard scan uP... so you can get the part number.
--
Roy Thistle


Re: Tek 2230, almost fixed but with a problem out of my competences

Albert Otten
 

Hi Federico,
Perhaps related: in your 1 Hz picture, why is the amplitude so low? Apparently there there is a lot of noise (50 Hz ripple?) since the peak limits are relatively so far apart.
Albert


Re: What ever happened to Larry "Christopher"... or at least his Tek stuff?

Roy Thistle
 

On Mon, May 31, 2021 at 12:22 PM, walter shawlee wrote:


I have not spoken to Larry Christopher
Thanks Walter!
I wasn't really looking to contact Larry.
Recent posts about west coast Tekmagnets piqued my curiosity.
Due to recent events, I was strongly wondering if I just imagined it all... cause Larry disappeared so suddenly... and without a trace... well relative to my tracing anyway.
It's good to know... I'm not confabulating!... yet.

--
Roy Thistle


Re: 1503B Backlight

Roy Thistle
 

On Mon, May 31, 2021 at 08:22 PM, Steven Bender wrote:


Most of these strips seem to have a full length double sided tape strip on the
back and flexible clear encapsulation on the front.
The "strips" are ubiquitous, across all the usual suspects... and if you live near civilisation, at the mall too.
There are different sizes and densities of the smt leds used... and the strips come in waterproof ( Chinglish for water-resistant ) or "stay away from water."
Making reliable solder connections to the strip's pcb can be a problem.
There are dimable/controllable... and the boards are widely available.
Hi-power led strips are widely used in LCD panels, for T.V.s and monitors... replacing CCFLs.

--
Roy Thistle


Re: 1503B Backlight

 

Roy Thistle wrote:

The electroluminescent green wire would be great for pimping out those orange painted 500s I read about.
Do not tempt me!

-- Jef Dutky

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