Date   

Re: Calibrating a PG506 w/o Sampling System

Chuck Harris <cfharris@...>
 

I use SD24's... primarily because they have a TDR source built into
them.... and TDR is way cool! But the cheaper SD26's would also be fine.

Don't forget your SMA attenuators! The SD's have a limited safe range
of input voltages.... +/-3V is it. Their maximum input voltage for
measurement is +/-1V.

Static electricity will finish off an SD so quick you won't even know
it happened. Use a wrist strap.

The "C" model is the pinnacle of the species. I wouldn't waste my time
on the plain, "A", or "B"... though you might because the prices are much
cheaper.. as are the CSA models... though with them you lose half the
plugin slots, as they are reserved for level shifters, and fiber optic
receivers..

-Chuck Harris

Rick wrote:

Chuck, the Tek 11801C is intriguing. What sampling head do you use or should be used for the PG506?

Rick






Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom,

Well, my neural net seems to be quite open to calibration, but my eyes are another story

I have actually been running tests (quantitatively unsuccessful, but qualitatively enlightening) on the visual bandwidth of my scopes (feeding in a Z-axis signal and seeing how many discernible dots I can fit across the screen), and this has really driven home what the actual precision of the scope display is (it's not more than about 9 bits in either direction). I recall my father saying something similar about the 4014 terminals that he used: the resolution of the drawing commands was 4k x 4k, but the actual screen resolution was much lower (I don't recall the exact numbers, but i now expect that they couldn't resolve more than 512 dots across the small [12 inch?] screens, and probably not more than 1k across the large [20 inch?] CAD displays we saw once at a Goddard open house). By my calculation the 400 and 2200 series scopes aren't actually displaying more than 640x400 pixels, and only 320x200 resolvable, distinct lines. This severely limits the precision of any measurements you make by eye on screen despite the apparent smoothness of the waveforms.

I'm still a little mystified by exactly what concrete tasks I might need a volts or watts per frequency measurement for, but I'm happy to wait for enlightenment while I play with a new toy. I'm a very hands-on learner, even when I'm rigorously going through theory need to have concrete examples to test myself against and to illustrate academically presented topics.

I see that there were two SAs in the 400 series, one much more "analog" (and of much older manufacture) than the other, and at least two more in the 2700 series (they look like siblings to the 2200 and 2400 series scopes). They seem pretty rare on eBay, and are asking much higher prices than the comparable era scopes. At some point I will need to read through the manuals for the 491, just to see how the spectrum analysis was done in the days before microprocessors.

Everything I have learned since taking up this hobby has fed a keen awareness that, even when they are in perfect working order, your instruments are lying to you (if only by omission).

-- Jeff Dutky


Re: Tek blue (and gray) paint

Jean-Paul
 

Hi there Nothing to do with the Virus, the regs are worse ever year as prices rise on shipping anything.

All common carriers Post/Fed/UP have tightened restrictions in recent years, eg Li batts, Haz mat, chemicals, and Aerosol.

Blame the liability lawyers.


Suggest to take the numbers on the can, check with a Pan-tone book, and get a custom (NON aerosol) mix at a good paint store.

Of course, it must be an oil based lacquer, so many jurisdictions (EG all of Claif) will prohibit due to VOC.

Will they ever just let us be to do our work?

Jon


Re: Calibrating a PG506 w/o Sampling System

Rick
 

Chuck, the Tek 11801C is intriguing. What sampling head do you use or should be used for the PG506?

Rick


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

Tom Lee
 

Jeff,

If you ever wish to examine the spectral content of a signal, you need an SA. Using a scope's presentation of a sinusoid, you'd be hard-pressed to resolve distortions below a percent, and you'd only do that well for certain types of distortion, and if your eyeballs and neural net are pretty damn well calibrated. A properly designed spectrum analyzer can resolve distortion levels in the ppm range (and still better ones exist). Better still, you see the nature of the distortion -- e.g., is the distortion dominated by a certain harmonic or group of harmonics? Is it not distortion at all, but interference or power supply noise creeping into the system? Etc.

So, depending on context, either a scope (for volts vs. time) or a spectrum analyzer (for volts vs. frequency) may be the right tool. If you have both, you've got both domains covered.

I should mention that some digital scopes have an FFT capability, giving you something that looks like what a spectrum analyzer would present. But there are many tradeoffs in trying to make a scope also act as a decent spectrum analyzer, so most scopes are not decent SAs. But if the software comes for free, one cannot complain too much, as long as one is aware that the instrument may present a screenful of lies.

-- Cheers,
Tom


--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/7/2020 23:54, Jeff Dutky wrote:
Tom,

I've had a look at the TinySA home page (www.tinysa.org/wiki), watched several of the recommended videos, and I'm sold.

I've just got one question: aside from using it as a signal generator, what would I DO with a spectrum analyzer?

-- Jeff Dutky




Re: Can capacitors

 

See also the earlier discussion on Multi section electrolytic capacitors:

https://groups.io/g/TekScopes/topic/multi_section_electrolytic/78408639

Regards,
John


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom,

I've had a look at the TinySA home page (www.tinysa.org/wiki), watched several of the recommended videos, and I'm sold.

I've just got one question: aside from using it as a signal generator, what would I DO with a spectrum analyzer?

-- Jeff Dutky


Re: Tek blue (and gray) paint

 

Dave Casey wrote:

I would think UPS Ground would take it, just as they do Lithium batteries.
I would have thought that too, and the seller seemed to expect that as well, but his impression was that they were refusing to ship aerosol cans during the pandemic. Whatever the case I will find out this week, as I plan to call both UPS and FedEx to verify what their current policies are.

-- Jeff Dutky


Re: Tek blue (and gray) paint

Dave Casey
 

I would think UPS Ground would take it, just as they do Lithium batteries.

Dave Casey

On Tue, Dec 8, 2020 at 12:28 AM Jeff Dutky <jeff.dutky@gmail.com> wrote:

I ordered some of the spray paint from the eBay seller, but he had to
cancel my order today because he can't find a shipper who will handle
aerosol spray paint. I was a little worried about this when I made the
order. I know that USPS won't handle such things, and I was worried that
UPS and FedEx might balk (which, apparently they have).

I am going to investigate UPS ground and FedEx this week, to see if there
is any way to ship these items, but the seller didn't sound optimistic.

-- Jeff Dutky






Re: Tek blue (and gray) paint

 

I ordered some of the spray paint from the eBay seller, but he had to cancel my order today because he can't find a shipper who will handle aerosol spray paint. I was a little worried about this when I made the order. I know that USPS won't handle such things, and I was worried that UPS and FedEx might balk (which, apparently they have).

I am going to investigate UPS ground and FedEx this week, to see if there is any way to ship these items, but the seller didn't sound optimistic.

-- Jeff Dutky


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom, Raymond, Harvey, and John,

This is an absolutely amazing wealth of information. I've already copied it into a notebook page, and will be going through it carefully over the next week (and trying to cross reference it to the 475A calibration process). This sort of information needs to be collected in one place and presented as a coherent alternative to the Tek-specified process (and, yes, I'm volunteering to do that).

Thanks for all this wonderful commentary and information. It almost sounds like I rolling my own calibration fixtures isn't nearly as challenging as I had feared it would be (probably much less challenging than buying the vintage equipment and restoring it to correct working order).

I've got a significantly-more-than-ten-dollar pulse generator (http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295&zenid=2cd5390de5b54cabb48f8ed903b80480) but I'm kind of excited to build the rest of the kit (I really need to get my feet wet with transistors, and I just finished reading about ECL for exactly this kind of project).

-- Jeff Dutky


Re: Anyone need 561 parts?

Bruce Atwood
 

I'm rewinding the HV XFMR in my 561 but would not mind a backup plan. How is the T600 in yours? As an aside, does yours have a 4.3 Ohm resister in series with the 1 turn secondary for the filament of the HV rectifier? Every schematic I see has one but there is no trace of it in my 561.

Fully OT: My 561 is almost all that is left of ITI Electronics (I also have their GR impedance bridge, a real marvel). ITI did TVs for bars and hotels in the late '40 and '50. My dad, Horace, W2SXW, was founder and president. One of the few small firms founded in the 40s that made it to the 80s. Dad told me of the IRE show where Tektronix showed of their first calibrated sweep, triggered sweep, calibrated gain scope where the assembled engineers all agreed it was a marvel but wondered who the hell would pay $ks for a 'scope. He was designing 'scopes for Allen B DuMont the time, later doing TVs for him.

cheers


Re: CRT static charge

Richard Knoppow
 

I wonder if the blue filter has a static filter on it or in it. Also, there are laundry softening tissues that go in the dryer that have anti-static stuff in them Wiping one on a meter face or CRT will often get rid of static charge. The tissues are often called anti-cling.
   If you have an ohm meter that will read very high resistance try it on the two filters to see if there is any difference in surface conduction.

On 12/7/2020 10:29 AM, Dave Peterson via groups.io wrote:
Something interesting noted on restored parts scope: when powered up the CRT seems to create a static charge crackling noise.

That is, my perception is that the sound is coming from the face of the CRT. This scope currently has a clear shield on it. My existing 465 with a blue shield does not crackle when started. Every component of the face of the scope has been freshly cleaned, so is presumably very dry and free of any oils from handling. The screen shield wiped with a glasses cloth you get from the optometrist to get rid of the static cling. Otherwise lots of dust would obviously accumulate. So presumably the shield has been discharged. The scope is properly grounded, including the ground plug on the face of the scope.

It sounds like fresh laundry being separated, but much quieter. It barely audible, but it's there.

Is this normal? I don't ever recall it from my previous experiences, but it's so innocuous sounding that I'm sure it wouldn't arouse much suspicion otherwise. I'm just very attentive to every sound, and very wary of anything with a scope of completely unknown origin and state. Could it be an indication of anything untoward? Haven't gone through a calibration yet. Getting ready to do so.

Dave



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


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

John Gord
 

For relatively slow (Hz to 10s of kHz) square waves of known amplitude, you can use some paralleled beefy CMOS buffers powered by a precision supply feeding a relatively low impedance multi-tap voltage divider. Output levels can be adjusted at DC with a DMM, then the buffers can be driven from a convenient function generator (or crystal controlled synthesizer if you want accruate timing). This is limited to 5v max or so with most fast CMOS, but 4000B series can be supplied with 10v or more if desired. (The 4000B series is not as beefy, though.)
--John Gord

On Mon, Dec 7, 2020 at 06:53 PM, Tom Lee wrote:


Hi Raymond,

You're not wrong about the need for lower frequency square waves if you
want to perform the full set of cal procedures. You'd have to supplement
the tinySA with a pulse generator, as you've noted. Luckily, the
performance requirements are pretty lax -- the frequency doesn't have to
be all that precise, and it's easy to produce good, clean waveforms over
the relevant frequency range. Homebrewing it would be entirely feasible,
and I wouldn't be surprised if there's a $10 pulse gen kit on fleabay.

I don't remember the frequencies needed for a 475, but ISTR numbers
between 1kHz and 50kHz. But when I homebrewed mine back in the day, I
used some TTL dividers driving a PNP (I used 2N3906s, I'm sure, since I
had a mountain of them) emitter-coupled output stage to feed a 50-ohm
termination. That stage cleans up the less-than-pristine TTL output to
provide a well-behaved square wave.

I guess you could even square up the 100kHz output of the tinySA to
drive something similar, and you'd be good to go.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/7/2020 18:29, Raymond Domp Frank wrote:
On Tue, Dec 8, 2020 at 02:53 AM, Tom Lee wrote:

from 100kHz to 360MHz (beyond that you get square waves)
Nice! Just an SMA-to-BNC and 50 Ohm feedthrough needed. I'd have to think
for which Tek 465/475 adjustments exactly, except for horizontal timing as you
describe and observing BW, if the TinySA produces something enough like a sine
wave, which I guess it does between 100 kHz and >300 MHz. For adjusting the
high-impedance CH1 and CH2 step attenuators, a frequency much lower than the
TinySA's minimum (@100 kHz) is necessary. For edge adjustment, using the
square wave could possibly have been nice but 360 MHz (the minimum square wave
frequency) won't make it through to the vertical amp in any useful way.

Am I wrong and/or missing something?

Raymond





Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

 

Tom,
Re. equipment (generators and passives) needed (I only checked for the 465):
- For adjusting the Hi-Z step attenuators' frequency behavior, the 1 MHz CH1 and CH2 inputs need to see a 20 pF capacitance. A 20 pF "normalizer" is needed with many people using their "reference" 10x passive probe, hoping it's set to about 20 pF or at least away from max or min capacitance. Source is a 1 kHz square wave generator. As you say, very lax requirements there.
Since adjustments need to be made up to the 5 V/div setting, a relatively high-amplitude, "good-looking" square wave is needed, especially when using a 10x probe. Normally, the high-amplitude output of a PG506 is used, with fixed attenuators as needed. Wave front (HF) and flat top (LF) are adjusted this way.
- A 50 kHz sine wave is used for determining the base deflection against which the BW is measured. I'm sure that 100 kHz would be no problem so 100 kHz and >=100 MHz from the TinySA may be used. Voltages up to 2 Vpp, so no problem for a TinySA. Just an SMA-to-BNC cable and 50 Ohm feed-through needed.

Raymond


Anyone need 561 parts?

WB4IUY
 

I salvaged some bits from an old 561 to restore my 564B, have a good bit of stuff left. wb4iuy@gmail.com

Dave WB4IUY


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

Dave Peterson
 

The first 465 I got was horribly, unusably, out of "cal". CH1 level disagreed with CH2 by something like 30%. At this point I had NO lab equipment beyond a DMM and some test leads. I was able to get a free function generator app on my cell phone and set levels that agreed with the output. CH2 agreed out of the box, CH1 needed adjustment. Is it to any kind of spec? No. Is it better than it was? Sure.

Time base was out of agreement too. It said my line voltage was running at 67Hz. I don't think so. Again, using the free FG app I got the scope within reason. I was also able to get trace rotation and geometry improved. And the line frequency is sensible now too. For 99-bucks I got a two channel 60MHz FG/counter with a plethora of waveforms, modulation, sweep, VCO, sync in, etc.

I have a long way to go before my bench is to my standards. But I don't mind making incremental steps. It's the journey.

Dave


Re: Tek blue (and gray) paint

victor.silva
 

I have some cans of Tek Blue that matches the 24xx series perfectly.
I posted a message it before.

I wonder if these can still be purchase given the information on the label?

It is Krylon OMNI-PAK MasterBlend EZ TOUCH <- This is the generic can for custom paints.

Specific blend is on a label which reads:

L61 Opex Lacquer
L61XXL42-4383
TEK BLUE
09/26/05


Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

Tom Lee
 

Hi Raymond,

You're not wrong about the need for lower frequency square waves if you want to perform the full set of cal procedures. You'd have to supplement the tinySA with a pulse generator, as you've noted. Luckily, the performance requirements are pretty lax -- the frequency doesn't have to be all that precise, and it's easy to produce good, clean waveforms over the relevant frequency range. Homebrewing it would be entirely feasible, and I wouldn't be surprised if there's a $10 pulse gen kit on fleabay.

I don't remember the frequencies needed for a 475, but ISTR numbers between 1kHz and 50kHz. But when I homebrewed mine back in the day, I used some TTL dividers driving a PNP (I used 2N3906s, I'm sure, since I had a mountain of them) emitter-coupled output stage to feed a 50-ohm termination. That stage cleans up the less-than-pristine TTL output to provide a well-behaved square wave.

I guess you could even square up the 100kHz output of the tinySA to drive something similar, and you'd be good to go.

-- Cheers,
Tom

--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 12/7/2020 18:29, Raymond Domp Frank wrote:
On Tue, Dec 8, 2020 at 02:53 AM, Tom Lee wrote:

from 100kHz to 360MHz (beyond that you get square waves)
Nice! Just an SMA-to-BNC and 50 Ohm feedthrough needed. I'd have to think for which Tek 465/475 adjustments exactly, except for horizontal timing as you describe and observing BW, if the TinySA produces something enough like a sine wave, which I guess it does between 100 kHz and >300 MHz. For adjusting the high-impedance CH1 and CH2 step attenuators, a frequency much lower than the TinySA's minimum (@100 kHz) is necessary. For edge adjustment, using the square wave could possibly have been nice but 360 MHz (the minimum square wave frequency) won't make it through to the vertical amp in any useful way.

Am I wrong and/or missing something?

Raymond




Re: SUCCESS! The "sick" 475A is now the "fixed" 475A!

Harvey White
 

Most oscilloscopes of that era are analog only, and as such, you measure things against a trace on a graticule, by eye.

I remember somewhere where Tek said that 2-3% was the best you could get in such measurements.

Go to digital, and while the timebases are digital, they may be derived from a non adjustable frequency source.

Your average time interval calibrator, when adjusted against a known frequency standard (WWV has been around for ages) ought to be more accurate in terms of absolutes than the scope.

That leaves amplitude and frequency response.

There are 10 volt references on EBAY (and equivalent) which can be  used to adjust a DMM/DVM.  With some compromises those could be used to adjust the scope's Y axis.

Should time response be needed, some very accurate risetime generators can be had.

You should be able to get reasonably close for a home lab.

Sometimes the purpose of calibration on a scope is to make sure that if you measure thing A on scope #1, it'll be the same on scope #2.

Harvey

On 12/7/2020 7:16 PM, Dave Peterson via groups.io wrote:
This thread is validating my suspicions. I was surprised to accidentally come across a cal service website offering calibration for a 465 while looking for what the waveform on TP1478 (or something like that) was supposed to look like. Part of the Z-axis compensation adjustment. As Jeff noted, they're available, for more $$ than I payed for the scope.

I'm sure I could adjust my scopes as well as, if not better, than a dedicated shop. But I know the difference is that I don't have certified standards to validate against. But then my balancing thought is what you're saying about 0.1% - how many significant digits can one achieve with these things. Trying to adjust a 465 pot to less that 1% is just not possible. Doesn't stop me from trying. Wink. But if I have two or three instruments agreeing to 1% I have good confidence that my adjustments are valid. But that's not really what "calibrated" means.

Again, the issue circles back to what one is trying to sell. If I sold as "calibrated" I wouldn't do that without: A) charging for it, and B) providing the paperwork proving it. I like the term "performance verified". Or otherwise functionally and performance verified or validated. I'll have to investigate what eBay calls "Refurbished". Then again I'm probably holding myself to a standard that other sellers may not. I gotta be me.

I've got a ways to go before I'll feel comfortable reselling a scope as refurbished and verified. I also don't see myself selling one until I am comfortable saying that. If I wasn't comfortable selling it as validated I'd have to sell it as parts. Which I'm also not thrilled with. I don't see a market for selling a "calibrated" 465 vintage scope. I'd leave that to the buyer. If they need that, then it's part of their operating expense anyway.

Thanks for your inputs. Enlightening, educational, and entertaining, as always.Dave

On Monday, December 7, 2020, 03:30:32 PM PST, demianm_1 via groups.io <demianm_1=yahoo.com@groups.io> wrote:
My experience with cal labs has not been encouraging. Mostly they want to run instruments through the automated cal procedure. Anything else will be expensive (labor). And its really whether the instrument is within tolerance (go/nogo). Its not adjusted to perfect.  If adjustment/repairs are needed the rate can be astonishing and keep in mind on these older instruments the repairs are not 10 minute fuse replacements. They are usually really difficult things to figure out.

However for a scope a time mark generator and a leveled signal generator would cover most tasks. CRTs are not .1% instruments so no need to get that involved. I picked up a Ballantine 6130 time mark generator and a Tek 191 leveled generator (to 100 MHz) pretty reasonably. With those you could say "performance verified" instead of "calibrated".








12141 - 12160 of 186332