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But Leo's pulser has a big advantage over the 067-0681-01 when it comes to sampling measurements
since it has a pre-trigger pulse that the 067-0681-01 does not.

Dennis Tillman W7PF

The other thing that you get from Leo is a copy of the waveforms with the rise and fall times. For
mine 28ps fall and 30ps rise.

But he seems to be out of stock with the BNC version - shows what the demand must be!

Craig

Hi Gerardo?I dont want to rip apart the scope and part out ,if you would like to buy the scope that has a few plugins thats fine , the only thing is it might too costly to ship to you as most things ar outside of the US .

Sent from Yahoo Mail on Android

On Mon, May 21, 2018 at 1:52 PM, gerar2182<gerardo_novillo@...> wrote: Hi Oliver

Im new in this group and i dont know if is? possible to speak about transactions here.

Im very interested. I live in Argentina. Here is not possible to get this part .

Please let me know how much you want for the CRT and how much for shipping to

Argentina , using USPS.

Also let me know how much for the Power Supply.

May be i will in need of the Readout Board and some knobs.

Im trying to come back to life a completely dead equipment.

Thank you very much.



Gerardo Novillo


________________________________
De: [email protected] <[email protected]> en nombre de oliver johnson via Groups.Io <nojjamaica@...>
Enviado: lunes, 21 de mayo de 2018 13:57
Para: [email protected]
Asunto: Re: [TekScopes] Tek 7904 CRT

Where are you locates i have a spare 7904 with ps out that i started to repair , crt is fine , i am in ny if you are interested.

Hi Oliver

Im new in this group and i dont know if is possible to speak about transactions here.

Im very interested. I live in Argentina. Here is not possible to get this part .

Please let me know how much you want for the CRT and how much for shipping to

Argentina , using USPS.

Also let me know how much for the Power Supply.

May be i will in need of the Readout Board and some knobs.

Im trying to come back to life a completely dead equipment.

Thank you very much.



Gerardo Novillo


________________________________
De: [email protected] <[email protected]> en nombre de oliver johnson via Groups.Io <nojjamaica@...>
Enviado: lunes, 21 de mayo de 2018 13:57
Para: [email protected]
Asunto: Re: [TekScopes] Tek 7904 CRT

Where are you locates i have a spare 7904 with ps out that i started to repair , crt is fine , i am in ny if you are interested.

I am in NY Long Island?

Sent from Yahoo Mail on Android

On Mon, May 21, 2018 at 1:19 PM, Pete Lancashire<xyzzypdx@...> wrote: where are you located ?

On Mon, May 21, 2018 at 8:14 AM, gerar2182 <gerardo_novillo@...>
wrote:

Somebody has a CRT PN 155-0644-05 or 155-0644-09 for a TEK 7904 for sale?
Thanks

Hi Craig,
I didn't think of this when you first contacted me but the Leo Bodnar Pulse Generator would be an excellent alternative to the Tunnel Diode Pulser. The only thing to take into consideration when using it to calibrate your scope is that the aberrations are greater for the Leo Bodnar Pulse Generator. They are roughly double what the 067-0681-01 aberrations are. The hardest part of creating a pulse generator is controlling those aberrations on the edges.

But Leo's pulser has a big advantage over the 067-0681-01 when it comes to sampling measurements since it has a pre-trigger pulse that the 067-0681-01 does not.

Also, Leo's Pulser is powered from any USB cable. So it doesn't need a high voltage pulse to trigger the Tunnel Diode circuit inside. That HV pulse source can be hard to find.

The Leo Bodnar Pulse Generator is something you can buy right now.

Dennis Tillman W7PF

where are you located ?

On Mon, May 21, 2018 at 8:14 AM, gerar2182 <gerardo_novillo@...>
wrote:

Somebody has a CRT PN 155-0644-05 or 155-0644-09 for a TEK 7904 for sale?
Thanks

On Sun, 20 May 2018 10:40:54 -0700, you wrote:

Harvey, thanks for your example. I do somewhat the same with a voltmeter in respect to measuring voltage drop/gain rather than doing the math, I can get higher resolution too since the decimal moves over.

Your high voltage idea in respect to exceeding limits; would it be possible to use the 2 channels to measure a floating high voltage that exceeds the single channel to scope chassis limit of say, 500V peak? Given a 1M channel impedance, do I end up with a 2M impedance? Could this be a method to cut scope loading on the DUT in half?

I am not happy with that use. Say you have 800 volts, you'd need to
find a 400 volt supply to "float" the scope, and measure the lower and
upper end with the scope probes. While you may not exceed the input
voltage maximum, the thought of a scope chassis somehow floating at
400 volts above ground, (OR your UUT having that kind of voltage
extent somewhere (as in scope chassis is 400 volts, UUT chassis is
-400 volts) is not a pleasant thought.

Again, a battery operated scope (double insulated) *might* be able to
do this, and likely would within the limits of (whatever voltage) per
channel. That would be the only use that I'd even consider, and I'd
go find the high voltage probes that are made to handle this kind of
situation.

In theory, you would get a 2 meg impedance, but even on a low voltage
circuit, I just have a feeling that this is a bad idea, measurement
wise.

Best practice and safest practice is to avoid putting the equipment in
this kind of situation.

Overall, my immediate feeling is "don't do this".

Harvey

And yes, this is an academic question, the examples help me to understand the testing possibilities with my scope.

NielsenTelecom

Where are you locates i have a spare 7904 with ps out that i started to repair , crt is fine , i am in ny if you are interested.

Sorry 154-0644-05 or 154-0644-09
Thanks

Somebody has a CRT PN 155-0644-05 or 155-0644-09 for a TEK 7904 for sale?
Thanks

It has been decades since we impedance matched audio lines in professional audio. When I began in professional audio nearly fifty years ago we impedance matched for 600 Ohms using input and output transformers in both tubed and transistorized equipment.

The cable used for balanced audio lines in broadcast and recording facilities has a characteristic impedance on the order of 100 Ohms. We now use voltage-sourced outputs rather than the power-sourced outputs of decades ago. Studio output impedances nowadays are on the order of 100 Ohms and inputs on the order of 10,000 Ohms.

David, your initial question concerned connecting an audio oscillator (you said signal generator but I suspect it is just an oscillator) with a 600 Ohm output. Depending upon the circuit design you may need to terminate it in 600 Ohms to optimize distortion and frequency response and simply bridge the 'scope input across that 600 Ohm termination.

I routinely impedance match RF circuits at work where cable lengths are significant fractions of a wavelength. I never do so at audio frequencies because I am not driving audio cables with wavelengths of thousands of meters. I do sometimes have to terminate audio outputs in older equipment with 600 Ohms in order to get them to behave properly in the modern studio environment.

At RF I routinely handle power output stages of up to tens of thousands of Watts, and impedance matching can be critical to maximize power transfer and minimize hating of the RF output stages. At the power levels you are working with at audio frequencies impedance matches are not critical to the power dissipation of output stages, and any output termination is normally done only to optimize the frequency and distortion performance of the stage.

Note that if you are using a true audio signal generator (such as the HP 651B that I use in the shop) the output must be properly terminated to maintain calibration, as Ted noted upstream.

Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA

I am having trouble donating! I can log in to paypal o/k but when I go via the vintagetek.org link I keep getting the run-around from interminable security tests - It's driving me mad. What do I put in to the paypal "send money" page to do it?
Thanks,

Geoff.

Can access it fine from the UK too.

No problem reaching it here?

--
Dave
Manuals@...
www.ArtekManuals.com

Is the website down at the moment? Cannot access at all.

Geoff.

Count me in. I've donated $100 because the museum needs to be supported. I'd recommend setting up a fundraising page for Tekscopes too.

Rick Bale

This


might help you understand where the 600 ohms came from.

It's unlikely that a consumer grade piece of audio equipment would be able to drive a 600 ohm input.

In the commercial sense, connections are usually balanced XLR's using 600 ohm transmission line.? You do have long cable to deal with.

The only real object is to have x volts p-p at the end of the cable, so you drive with the lowest impeadance into something reasonable like 10K.? Tubes were an entirely different animal.

With a power amp, you have say an 8 ohm speaker and 100 W/ch, both channels driven.? If I had an 8 ohm output Z at my amplifier that would not be very good.? So, I really need the lowest output Z.? This is actually expressed as Damping factor.? A damping factor of 100, means the output Z of the amp is 8 ohms/100.

Speaker impeadance is actually measured at 1 kHz and is usually about 6 ohms for an "8 ohm speaker".

We also have losses in the wires going to the speaker.? We don't have sense leads in our audio amplifiers.

Professional audio is usually more precise.? So, the output is assumed to be driving a 600 ohm balanced load.? That's not the case in consumer audio.

==

A comment about scope impeadance.? Two standards exist of 1 M and 50 ohms.? They may have different parallel capacitances.? 1M || 22 pF is common.
Why the capacitance?? We try to create the perfect voltage divider.? So of the scope has 1 M || 22 pF and the probe has 1 M || with x-22 pF, then it's possible to create a near perfect divider at "all" frequencies.
? By doing probe compensation (vary the capacitor on the probe with a square wave input such that the waveform is square) does just that.? In return, we get a probe that sees 10 meg ohms resistive and attenuates the signal by 10x usually. ?? The scope probe cable has capacitance too.

==

You also need to remember a couple of things:
Twisting helps eliminate EMI because the EMI radiates into both conductors "equally" and the differential receiver removes the common mode signal as well as the act of twisting.

Shielding reduces EMI.? Shields should be connected at one end only and this is typically the signal source.

Thus, twisted-pair shielded cable is very common for process control and professional audio too.

Ground loops are really our enemy.

A square wave by Fourier analysis requires infinate bandwidth to re-produce.
It's made up of the sum of the odd harmonics of sine waves.

Bandwith is usually measured at the -3db frequency or when the signal is down by ~0.707.? there is a rule of thumb that relates rise time and bandwidth.? See:
Worry about stuff when it's important.

Is three resistances in series e.g. 3K equivalent to three 1K resistors in series??? I can argue no and be right.

Does a moving wire in free space on earth develop a current???? The answer is yes.? The practical answer is no.? It is a wire that's rotating in the Earth's magnetic field, so it generates a current based on physics.? Have I measured such a current - Yes.

In a college glass we had a test and I successfully argued that my answer was correct. ? His answer was, "Your not supposed to know that yet."

Donated.? It's useless to have such a resource that is untappable.? I would not mind donating to Tekscopes either.? What was addressed before, too bad there isn't an index or even tags for posts.

Here's the link to post from Sergey Kubushyn<>:




It's probably also somewhere on groups.io if you search for it...I was too lazy to go look it up.


Jeff

________________________________
From: [email protected] <[email protected]> on behalf of John Griessen <john@...>
Sent: Sunday, May 20, 2018 7:43 PM
To: [email protected]
Subject: Re: [TekScopes] Wanted 067-0681-01 Tunnel Diode Pulser by new member

On 05/20/2018 09:41 PM, Jeff Davis wrote:

Hi Craig,

You can easily build one in just a few hours. The only challenge is obtaining the right tunnel diode (eBay), mounting it (use conductive epoxy), and confirming the rise time is within spec (I borrowed a high speed scope from my work for this). The other parts are garden varieties obtainable from Digikey.

I built two of them but sold the second on eBay.

There was a great posting by one of our members, Sergey, on this. I don’t have the details handy where I’m at but

Please put the link here also.

On Sun, May 20, 2018 at 07:27 pm, Craig Cramb wrote:

Looking for a working condition Tektronix 067-0681-01 Tunnel Diode Pulser for
doing the Cal 6 on a 2400 series scope. I have all other tools but am missing
this tool to complete the full calibration sequence. Please reply to
electronixtoolbox@...
if you can help.
My background is 42 years working in the HVAC industry. But I have had the
hobby for about 25 years learning about and repairing Tektronix scopes. Not an
expert just have some experience of a lot of trial and error getting them
working. I started with the 475 model and with a manual and advise from Reed
D. Learned how to navigate thru the Tek manuals and have been somewhat
successful at repairs. Since then I went to the T900, 455, 465, 2430/A,
THS700, 222 and onto the 2400 series. Which now I mainly deal with the 465 and
2465b,2467B scopes. Over time I’ve acquired TG501,PG506,SG504,SG503. Several
that are non working and still don’t work today and some that are fully
working. I seem to not have the knack of fixing plug-ins.
I have many scopes that I need to repair in my shop. I just hate to see them
parted out or thrown away when the majority can be fixed with a fair amount of
time and effort. I’m not retired yet but hope to be soon so I then can spend
more time with the units in my shop.
If you have made it this far in this note. Thanks for reading and ask any
questions you have.

Craig Cramb
Wichita,Ks

Not easy to come by, as you have seen. Someone here may chime in on this guys pulser I personally know nothing about it but it seems some people here use it.