Date   

Re: Asking for Help with Verifying Genuineness of 2465B from Ebay

Tom Gardner
 

On 22/12/20 05:37, Tom Lee wrote:
If you want to know the bandwidth, then measure the bandwidth.
And the question becomes, "why do you want to measure the bandwidth?"

Firstly a scope is a time domain instrument, and (arguably) the most important characteristic is fidelity of what is seen in the time domain. Usually that implies some variant of transient response. If there are no transients, then use a frequency domain instrument such as a spectrum analyser.

Secondly, "bandwidth" is a single number that is used as a simple proxy for the complete amplitude/phase vs frequency response.

So, work out what you measurement your system/UUT needs, and then work out to what extent the measuring instrument enables you to measure it.


Re: New Tektronix Curve Tracer Adapters - Semiconductors and Vacuum Tubes

Glydeck
 

Very nice. Your adapters look first rate. — George

On Dec 21, 2020, at 5:03 PM, Jean-Paul <jonpaul@ix.netcom.com> wrote:

Christian bravo pour le projets. Wonderful to see a Tektronix afficanado, who appreciates curve tracers.

I did similar 577, 576 test adapters in 1980s, using two pieces of lucite 1/4" and hand wiring the Bannana plugs.....TO-3, TO-66, TO-220 and TO-247(?) also, power diode, and a very useful binding post adapter. But I didn't have your tube socket idea.

The Kelvin connection four terminal is critical for high current tests, 2 terminal will give substantial errors in the voltage at the contacts points. The two terminal limits are perhaps one amp. 576 with 177 pulsed test fixture has 1000A peak capability!

Note...The 576 and 577 plastic safety test fixture cover is easy to damage and a problem in testing large power devices or with long leads. I modified my 576 with an interlock "cheater" switch..DANGER DO NOT DO THIS... At the time I was designing and manufacturing 12 kw arc lamp power with 55 kV ignitors, so the 576 voltage was not worrying!

The 576 is still in mint condition, I got the original manuals, 177 pulsed current and SCR turn-off time adapter.

Keep up the fine work. Just the ramblings of an old retired EE

Jon










Media Rate postage was always part of the plan

 

In the first email I sent out that had specific details for paying for
Peter's book I had already been to the Post Office three times to find out
what the cheapest postage would be for domestic shipments. The answer is
Media Rate which is about $4.00. The exact price depends on the "postal
zone" it ships from and the "postal zone" it ships to. These zones are not
the same as zip codes but they are somewhat related.
Dennis Tillman W7pF

Sent: Sunday, November 22, 2020 8:15 PM
Subject: DOMESTIC {AYMENT INSTRUCTIONS for Peter Keller's CRT Book

<SNIP>
DOMESTIC UNITED STATES PAYMENT INSTRUCTIONS
The total amount is $37.00 per book. ($30 for Peter's book,
$4 for media rate postage, $3 for mailing supplies and my time).


Re: Asking for Help with Verifying Genuineness of 2465B from Ebay

Tom Lee
 

It's important to understand that the relationship between rise time and bandwidth is not as quantitatively solid as many seem to think. The oft-quoted "-3dB BW in hertz, times the 10-90% rise time in seconds = 0.35" applies to a single-pole RC system driven by a perfect (zero rise time, zero overshoot) step. For the mathophiles among you, it's (1/(2*pi))(ln(9)). If your system isn't single pole, the relationship will be different. If you're not driving it with a perfect step, the relationship will be different. Since you never have a single pole, nor a perfect step, you're actually in approximation territory in practice.

Occasionally, you will see reference made to a Gaussian response conforming to the rule of thumb above. I think I've even seen it in some Tek literature (although I may be mistaken). Strictly speaking, the constant changes from 0.35 to 1/pi, or about 0.32. But that's purely of academic interest; true Gaussian responses do not actually exist, so you're still in approximation territory.

So, you're not measuring bandwidth when you measure rise time. You are estimating it. Preserving many digits in the computation is, therefore, actually kind of silly and pointless. You may be calculating a 3-digit answer to a 1-digit question.

If you want to know the bandwidth, then measure the bandwidth.

-- 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 12/21/2020 17:44, Raymond Domp Frank wrote:
On Tue, Dec 22, 2020 at 02:13 AM, Raymond Domp Frank wrote:

So ideally a 2465A should be producing a risetime measure of 1ns and I'm
getting 1.09ns.
It's incorrect to say BW can be measured by measuring rise time. It depends on the 'scope's characteristics, the exact step shape (slew rate, over/undershoot, flat). Rise time gives an indication of flatness across a certain frequency range. In practice, direct BW measurement/specification is used and an approximate derived rise time is given. The TDS3000-series comes to mind but there must be many others.
Why is that?
Observe a sine wave, with a frequency known to within a few percent, with constant level at the 'scope input, and make sure that impedances of sine wave generator and 'scope input are well matched.
Observe the amplitude on the 'scope, starting from a frequency where the 'scope has "100% amplitude" and increase the frequency while observing the decrease in amplitude on the 'screen, until the amplitude is 100% - 3 dB, or about 70.7% of the original amplitude. There's your upper BW limit. In practice, you'll almost always see some wobbling when approaching the upper frequency.
Once you've established BW, go specify the approximate rise time, using 0.35/(rise time) for 'scopes with Gaussian behavior (simple roll-off). For your digital 'scope, use 0.40 or even a bit more. That's because the filtering in these 'scopes is (and must be) steeper, partly to avoid aliasing above BW-frequency.

Raymond




Re: Interfacing 576 Curve Tracer to 7633 Storage Scope

 

Hi Raymond,
I'm sure you are right that all D40 display units had the DB-25 cutout on them.
I wonder what it was used for?
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Raymond Domp Frank
Sent: Monday, December 21, 2020 6:36 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Interfacing 576 Curve Tracer to 7633 Storage Scope

On Mon, Dec 21, 2020 at 09:55 AM, Dennis Tillman W7pF wrote:


It was easy to find the right spot in the vertical amplifier circuit
and in the horizontal amplifier circuit to connect to and bring them
out to a DB-25 connector since, for some reason, my particular 577 had
an optional factory installed DB-25 cutout with a cover plate since it
was not actually used for anything. I never noticed this before that
moment and I can't say I have ever seen it on any other 577.
I have a D40 display unit (5440 'scope) with a horizontal DB-25 cutout in the cast aluminum rear chassis (not the cover plate) below the CRT socket cover.

As is well known, the 577 uses 5xxx display units so the cutout may have been standard (from a certain date).

Raymond







--
Dennis Tillman W7pF
TekScopes Moderator


Re: Asking for Help with Verifying Genuineness of 2465B from Ebay

Chuck Harris <cfharris@...>
 

Hi,

The transient adjustments are never going to result in
a perfectly square waveform from the tunnel diode pulser.

In the first place, no pulser is perfect itself.

Typically, transient response is majorly affected in several
areas. There is a chomp out of the top of the waveform that
is caused by the spacing of the leads leading to the deflection
plates. The interactions are very many.

You can tell what does what by touching various parts of the
circuit with a small piece of metal on a wooden stick... or
use one of the diddle sticks that has a small metal blade.

I find that the more perfect the square edge, the slower the
transient response. You have to leave a little peaking, and
a little ugliness in the top to get the better than 1ns risetime.

-Chuck Harris

Mr. Eric wrote:

Chuck,

When I take the rise time measurement, I'm using the var knob of the volts/div in order to scale the flat top and bottom of the squarewave to the 0% and 100% graticules. I then use the deltaT cursors at the intersection of the 10 and 90. I will give a thanks and shoutout to W2AEW for his videos that teach these things. I've been wondering for half my life on why I would want an uncalibrated volts/div....

So ideally a 2465A should be producing a risetime measure of 1ns and I'm getting 1.09ns. That's unfortunate. Is it possible for this to be calibration or a dying cap in some filter in the front end? I will say that the inside of this scope is pretty clean which was really nice to see...

The only things I have for testing is the Leobodnar 30ps pulser and HP 8656A Signal Generator 0 to 990Mhz that has a calibration sticker from 2013 that says, calibration not required, for reference only =)







Re: Thoughts About Modern Tek Scopes

 

Raymond,

I was aware that sample rate was the important factor in DSOs, but had never heard an explanation of waveforms-per-second. That really makes the older DSOs look like a terrible value. I had expected (naively) that sampling and storing would be continuous and that calculation would proceed in parallel, or even have hardware support of some kind to keep pace with the sample rate. Everything that I'm learning about the early DSOs and the analog storage scopes that preceded them has been eye opening. I had always wondered how the early DSOs (e.g. the 2220) could get away with having a sample rate that was a fraction of the Nyquist frequency for the analog bandwidth, but seeing the limits of analog storage scopes put that in perspective. My instinct had been that digital scopes from the 90s and 2000s couldn't possibly compete on both price and performance with the modern, cheap Chinese scopes, and it sounds like I should trust that instinct.

I know nothing about the LeCroy scopes, except that they frequently appear in EE videos I see on YouTube. They seem to fetch real money on eBay, even the ones that appear to be in poor shape, so I haven't been paying them much attention (I'm saving up for the Siglent, after all).

Thanks for the detailed response, it was even more informative than I had expected.

-- Jeff Dutky


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

 

Dave,

Yes, I am not going back to the scope tonight. I will need to crack open one of the parts mules to get a replacement Q1338, and I am too frustrated to commit to that right now.

Thanks for saying that the part was probably already weakened. That had occurred to me, and whether or not it's true, I'm going to keep telling myself that for the rest of the evening. Of course, breaking this scope (again) isn't really a loss (though I was getting comfortable with the idea of having a working 250 MHz scope on my bench) because a. this was a parts scope from the start, and b. I'm working on it in order to get exactly this sort of oafishness out of the way before I do any work on my father's 475 (which I would really feel bad about breaking).

My method for having such interesting repair experiences was very simple: I just bought the cheapest, most beat up looking scopes I could find on eBay that seemed to fit with the theme of having parts mules for my dad's two scopes. Then I expanded the criteria very slightly to include some scopes that had interesting features and could serve as test scopes when working on the 475 (my dad's 2213 is a little too slow for that, as is the 2215A, but the later has the ALT horizontal mode that I wanted to play around with. The 2236 is just fast enough, at 100 MHz, has the coveted ALT mode, and has a pretty nice DMM/CTM module with a spiffy vacuum fluorescent display). I wound up having to fix both the 2215A and the 2236 in interesting and educational ways, and now both scopes are solid and being put to good use (the 2236 still has some work that needs to be done, but nothing that impairs its function).

I know that getting scopes from eBay is expensive and risky, but I think I've gotten my money's worth out of the ones I bought, and not merely because I put some effort into haggling (which I did, but most of my offers were accepted instantly, which means they were still too high). I've looked for other sources in my area, but there just doesn't seem to be very much in the DC area anymore. Craigslist was a complete bust, the University of Maryland surplus outlet has been barren of such things for a decade (and has been closed, along with the rest of campus, since the pandemic hit), the various government agencies have been similarly empty for cool stuff (you can get lots of recent but still obsolete computer crap, but nothing interesting), and I don't think that there's been a hamfest in the area in close to a decade (used to be a great one in Timonium, north of Baltimore).

The waveform is certainly a clue. It appeared to be composed some higher frequency signal modulated by the sweep and retrace: that moire pattern is not an artifact of the camera, and it was moving with some kind of beat frequency (rolling quickly, slowing down, stopping, reversing direction). I expect that the floor on the high segment was telling us something about the inadequacy of something in the z-axis amplifier, and I'll bet I can guess what. Changing the INTENSITY setting would shrink or expand the waveform vertically, and shift the floor on the high segment relative to the ceiling on the low segment. Changing the Time/Div setting would change the period of the waveform. I think that what we are looking at is the blanking interval (the left hand high segment) and the drawing interval (the right hand low segment), though I might have that backwards.

That waveform is actually one of the most interesting things I've gotten up on the scope since I started poking around earlier this year. It's really got a lot going on, and I could probably tell a lot more about it if I were better with the scopes than I currently am.

I've been hand copying sections of the schematics into my notes, partly to familiarize myself with the circuit by muscle memory, and partly to have the circuit somewhere that I felt comfortable adding notes to it (I'm not the kind of person who writes in books). I even made approximate hand copies of the PCB photographs so that I would have an annotated map of where the components of interest were. I'm especially hamstrung because my current workbench is ad hoc, set up in the unused kitchen that adjoins my office. There's no room for a computer on the kitchen table I call a bench, so I need to shuttle back and forth between my office, where I have manuals open on screen, and the bench. It's easier if I copy the important parts into my notes which I can have with me at the bench. It will be better when I vacate the upstairs (so my daughter can take it over) and return to my former basement office. There will be space for an extended bench and computer desk, along with plenty of shelving for scopes and other bits.

-- Jeff Dutky


Re: Thoughts About Modern Tek Scopes

amirb
 

I second Raymond's recommendation
more specifically I recommend a Siglent. My SDS1202X-E served me extremely well as my very first digital scope
and it came with tons of features and options as standard like all those serial triggering stuff or segmented memory etc...really great features and no need to hack anything
and I learned a lot from those. It is very small and light, quiet and yet pretty damn fast update rate and 14M record length. And 1202X-E is considered quite old now!
for digital work up to a few 10s of MHz or for switching power supplies or other analog work, a 200MHz siglent is a perfect choice. if you can get a MSO
then you also have a full blown logic analyzer at hand as well analog channels...if you do digital work, I think you do want to have some of the serial triggering and decoding stuff. Some of these old Tek scopes do not have those or some need to be hacked to enable them.


Re: Thoughts About Modern Tek Scopes

 

On Tue, Dec 22, 2020 at 05:09 AM, amirb wrote:


yes and their close siblings TDS7000
Not just the PC-part but the actual acquisition? Haven't found that.

Raymond


Re: Thoughts About Modern Tek Scopes

amirb
 

On Mon, Dec 21, 2020 at 11:06 PM, Raymond Domp Frank wrote:


On Tue, Dec 22, 2020 at 05:03 AM, amirb wrote:


there are already tons and tons of info on upgrading and hacking these
TDS5000
on other forums, so that has already been done (long ago actually)
I know about the TDS3000 series, but the TDS5000 as well?

Raymond
yes and their close siblings TDS7000


Re: Thoughts About Modern Tek Scopes

 

On Tue, Dec 22, 2020 at 05:03 AM, amirb wrote:


there are already tons and tons of info on upgrading and hacking these TDS5000
on other forums, so that has already been done (long ago actually)
I know about the TDS3000 series, but the TDS5000 as well?

Raymond


Re: Thoughts About Modern Tek Scopes

amirb
 

prices of used scopes never go up because of "paying attention" to them or praising them on this forum or other forums.
the only things that raises their prices are publishing repair or upgrading info/methods and hacking options or BW.
there are already tons and tons of info on upgrading and hacking these TDS5000 on other forums, so that has already been done (long ago actually)


Re: Thoughts About Modern Tek Scopes

amirb
 

On Mon, Dec 21, 2020 at 03:59 PM, Roy Thistle wrote:


On Sun, Dec 20, 2020 at 10:06 PM, Jeff Dutky wrote:


but just saw a TDS5054 on eBay for about the same price as the Siglent scope
I've been thinking about.
A lot can happen in 6 days on Ebay. My guess is it won't go for less than
1000.00USD... which is a lot more than a Chinese manufactured oscilloscope,
sold by a Chinese company.
tds5054 for $1000!!!?? who in the world would buy that? That would be a rip off. Even TDS5104 doesn't sell for that kind of cash. This is not TDS7000 series,
although even TDS7054 is not worth $1000 today...


Re: Thoughts About Modern Tek Scopes

 

On Tue, Dec 22, 2020 at 03:24 AM, Jeff Dutky wrote:


I assume, however, that you think the prices would go up because you would
praise this scope.
Hi Jeff,
My post really was meant tongue-in-check, in reaction to Roy Thistle's earlier post. We've seen prices of some models of equipment increase after more attention was paid to them on the 'net. It's a familiar market process.
The second point in my post referred to the relative ease of repairing a (switching) power supply as opposed to the difficulty to be expected when trying to repair an acquisition board, exacerbated by the lack of replacement components. The internal PC often can be replaced.

Regarding BW needed: There is a rule of thumb that says that at least 5 x the highest frequency component that you want to see in some detail determines the BW you need.

As regards DSO's, especially for digital applications, a few points:

I don't personally know the TDS5000 series and haven't studied their characteristics. Some say that the fact they "run on" a PC is a disadvantage. I have no reason to agree without having further information.

For analog 'scopes, BW is (almost) everything. Much less so with digital 'scopes. With digital 'scopes, samples/second is of paramount importance because it's the one feature that determines the ability to see short, one-shot events in any detail. As an example, a 400 MHz DSO with a maximum real-time sample rate of 200 Msa/s (like the old TDS400 series) is ok for watching a periodic square wave with a rise time of say 5 ns but useless for a one-shot observation in that range. "Equivalent Time" sampling won't help in real-time situations of course. If you want to see an edge or inspect a possible setup violation in a digital system, even running at only 1 MHz (your 6800), you need to resolve that time in enough detail, especially in one-shot or jitter situations.

Next come trigger capabilities. I rate those above memory depth because triggering makes acquisition selective.

Another important factor is "number of waveforms per second" (wfm/s). In contrast with analog 'scopes, DSO's, and especially early ones, had a very long time between subsequent "scans", since they operated in a sample one dataset - then store - then calculate - then present - and sample again. Repetition frequencies of less than 100 Hz weren't uncommon for 1 GHz DSO's (TDS680)! Most of the time, the 'scope was "blind", causing events happening during that time to be missed. Modern DSO's can perform at least at 10,000 wfm/s, many at 100,000 or more, so very little blind time. With strong triggering capabilities, the disadvantage can be mitigated.

There's a limit to the attractiveness of analog metaphors in digital 'scopes. I'm quite fond of the late-90's / early 2000's LeCroy 'scopes. They're really digitizers with piles of ways to process the digitized data. They're nothing like an analog 'scope - gone digital but are quite suited to a scientific approach, based on their digital nature.

I recommend you start by looking for one of the modern affordable Rigols or Siglents. They'll give you lots of fun and measurement info and convenience. Analog 'scopes are still worthwhile (apart from fun in their repair and restoration) because there's nothing more useful with newer models but with DSO's, development has been steep rather recently and cost/feature has come down. Just be prepared to meet bugs...

Raymond


Re: How much does 106 of Peter Keller's CRT books weigh?

Jack Reynolds
 

Dennis,

For heavens sake, you have already had your quota of pain and suffering on this exercise!  I for one really appreciate all that you have done so far.  Give it a rest until after the holidays.  I know that of things I have ordered for the last month and the delivery delays, I doubt that USPS will be caught up by mid January.  It took them two weeks to get a package to me from 350 miles away.  Pony Express could have done better.

Thank you again,

Jack

On 12/21/2020 4:33 PM, Dennis Tillman W7pF wrote:
My original idea if I got orders for 10 to 15 of Peter Keller's CRT books
was to have him ship them to me and I would mail them out to the individuals
who ordered them.

(Please feel free to form a line and kick me for what happened next. You
might say I was off by a little bit!)
My bright idea to get a few of these wonderful books into member's hands
worked too well. I had 20 orders by later that first day. Job well done I
thought to myself. If only it had stopped there!

By the time the flood of emails finally stopped I had payments for 106
books. In postal terms this comes to five boxes of 20 books each weighing
42lbs (19Kg) and one box of 6 books. Total weight 222Lbs (101kg). The cost
to ship this to me was going to be VERY expensive.

I needed a new plan and fast. So I decided to drive to Peter's house to pick
them up. He lives exactly 4 hours, 191miles (307km) from me. It was nice to
see him and his wife in person once again. Plus this gave me a chance to
talk to Peter about optical experiments he used to do at Tek measuring the
response of phosphors. Peter also designed the optical portion of the J16
Digital Photometer and its optical heads as well as the J17 and J18.

I went to the Post Office today to check it out. The lines are impossibly
long with people mailing presents. That will not change until after
Christmas (Dec. 25 in the US). Since it will take me a few days to put the
books in corrugated mailers I should be ready to face the window clerk at my
local Post Office on Monday. I'm not sure how he / she will react when they
see me wheel in 106 individually addressed books but it will be a long
morning for both of us.

Dennis Tillman W7pF




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

Dave Peterson
 

Rats, I hate when that happens. That's usually when I put things down and walk away. Time to clear my head. Hopefully if something is broken now it will be easier to identify.
When Time/Div is in X-Y the diode CR1337 is going to clamp it's cathode to "one diode drop" down from ground - based on intensity setting (could be higher?). So it's clamping the intensity output to no lower than -0.7v instead of -8.0v. Well, whatever the output of the intensity pot and divider is.
The take away is that raising Q1338 emitter reduces intensity, lowering it increases intensity. For example, the chop blanking would inject current into the intensity divider on Q1338 emitter raising the voltage and reducing Q1338's base/emitter bias and collector/emitter current. And then, yes, the output of this stage looks like negative voltage increases intensity - as per the function of the Beam Find switch. But seeing only a 300mV swing on Q1338 emitter seems small. My analytical skills for these circuits isn't up to snuff at this point tho.
I think you're on the right track. Sorry I'm not much help at this point. This is the sort of thing I'm getting into these scopes myself - to learn and relearn these circuits I think you either reactivated the existing failure mode that damaged the Z-axis amp in the first place, or stressed something else that was already failing. In the first case you know there's something causing the original failure. In the second you found another problem. This is actually a good thing if you want to learn this stuff. Can't fix what ain't broke. I'm a bit envious as I'd enjoy having this on my bench to debug.
I'm noticing in the picture you posted that the bottom of the narrower pulse on the left side of the screen is lower than in the picture in the calibration procedure. Not sure if it's significant, or a clue. I'm a bit mystified by that waveform. I've never seen such a thing. Not sure what that behavior is. A high frequency signal modulated by a much lower frequency pulse? Do you have to use the HF reject trigger coupling? The 465 cal procedure doesn't include this, so I'd have to familiarize myself with the cal procedure and corresponding circuit. I'd be doing what you're doing, poking around and studying. I doubt you broke anything that wasn't already marginal. One thing I was thinking of doing was printing schematics of circuits I'm working on and taking my own notes on them. There's a lot of things going on and getting it on the page may reveal issues a little more clearly.
Let us know any new findings.Dave

On Monday, December 21, 2020, 04:36:12 PM PST, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dave,

I'm not sure I entirely understand the effect of the X-Y Time/Div switch: in my diagram there's a diode in series with the switch leading to the emitter of Q1338 and the center tap of R1335A (INTENSITY adjustment, forward half). It looks like setting X-Y mode should cut off the negative output of the INTENSITY adjustment. I will verify that that happens at the node joining R1336 and R1337.

What I can figure out from the schematic is the following:

1. X-Y setting clamps the lower range of the INTENSITY pot to ground
2. A positive voltage on Z-axis input should put a negative voltage at the emitter of Q1338, even in X-Y mode (because of R1337?)?
3. other negative blanking signals also still affect Q1338 even in X-Y mode for the same reason?
4. the BEAM FINDER button clamps the amplifier output to -8V, meaning that low voltage is high beam intensity?

Obviously I'm just guessing at a bunch of this. I'm really out of my theoretical depth on this schematic (I'm much better if I just poke around with a meter and scope).

The original issue with the 475A (after I fixed the 110V rail) was that the entire beam intensity system was not responding to either blanking or to front panel control. That was largely fixed by replacing some blown transistors and diodes, but it's entirely possible that I missed something, or that my fix changed something. There are a number of notations a different points in the z-axis amp indicating a voltage at a node, but I don't know if this is a minimum, maximum, or average voltage. There are also a number of scope display sketches that I think I have figured out how to read.

I have put pictures of what I get on the test scope with the settings specified in step calibration step 7: Adjust Z-Axis Compensation in the photo album "475A DIY Calibration Adventures" https://groups.io/g/TekScopes/album?id=258453

The trace on the scope is similar to, but noticeably different from what I am led to expect in the service manual, specifically the lower edge of the upper segment (on the left) should, according to the manual, be offset several divisions above the upper edge of the lower segment (on the right). I think that's happening because I was not able to correctly adjust the grid bias in step 3.

The output of R1375 should go from 0V to +50 V, but its lowest range is about .36 V. It's highest range is +50V, but it's currently cranked all the way over the low end just to get a visible dot during the grid bias process.

I have verified that the INTENSITY pot drives its output from -8V to +15V, as expected. It looks like the emitter of Q1338 is only being driven through a range of a bout 300 mV (-2.0 V to - 2.3 V), but it also looks like my poking around has blown something out in the z-axis amp again, as I no longer have a trace on screen, even when depressing BEAM FINDER.

Well, I can't complain about being bored, at least.

-- Jeff Dutky


Re: Thoughts About Modern Tek Scopes

 

Raymond,

all the scopes I'm watching have "Buy It Now" prices, so I doubt there will be any immediate increase.

I assume, however, that you think the prices would go up because you would praise this scope. I'd really like know what your experience with them is, what you like, or what you dislike. I've also never used a modern DSO, or any scope that runs much of an OS on a microprocessor (maybe my 2236 just barely counts, as it has a 6800 running the DMM/CTM board, and real, honest-to-goodness firmware that boots when you power the thing on, but that doesn't have much, if anything, to do with the rest of the scope), and I don't know how much the OS intrudes on the user experience: it could be completely imperceptible (if done well) or it could be overwhelming.

My impression of the Rigol and Siglent scopes, from watching videos of people using and demonstrating them, is that the OS is completely buried under the custom interface, and that some care has been taken to replicate a classic scope like experience (with the exception of the use of multiplexed controls, soft buttons and on-screen menus, but even there the illusion of a scope with on-screen readout appears to be preserved).

It's also not clear to me that the extra 250 MHz would be very useful to me, but I'd rather have the headroom than not. I expect to be working with digital systems operating in the low single digit MHz range, since that's were my (entirely idiosyncratic) interests are.

As for the non-working scope, yes, I would want a significant discount on that (though the issue sounds like it's with the computer side of the system, which I feel a little more comfortable fixing than if the issue were with the acquisition board).

I'm also curious about how much I will need to shell out for appropriate probes. I've been able to get by with a combination of my father's old probes, a few cheap used probes of original Tek manufacture from eBay, and some very inexpensive modern Chinese probes from Amazon for the 475s and 2200s, but 500 MHz probes, even the cheap Chinese kind on Amazon, are edging up into real money.

Also, I wonder if the experience of using the scope at higher bandwidths is going to be different from my experience with 100 and 200 MHz scopes. I've already had to learn a bunch of things about how to probe signals just at the 1-5 MHz range that I never would have figured out on my own.

So I'm kind of talking myself out of the TDS5054, for the same reason that I talked myself INTO the Siglent SDS1204X-E: the extra couple hundred dollars I pay for the 200 MHz Siglent (over its 100 MHz sibling) gets me four 200 MHz probes that I would have to buy separately if I tried to save money by hacking the SDS1104X-E. Similarly, the cost of an eBay TDS5054 is actually higher by $250-$500 because I need to get probes for it (few of the eBay scopes come with probes, which I suppose I should feel angry about, but knowing how people mishandle their probes, I'm not sure it matters very much. Even my father, who always treated his instruments with the greatest care, managed to kill one of his P6075As eventually).

-- Jeff Dutky


Re: How much does 106 of Peter Keller's CRT books weigh?

Vince Vielhaber
 

1st class is only good to a pound, I thought Dennis said these were over 2 lbs.

Vince.

On 12/21/2020 08:00 PM, G Hopper wrote:
Click and ship does not have a on-line media mail price. The only option
via click and ship is first class and that's going to be more expensive.

G

On Mon, Dec 21, 2020 at 4:23 PM shalopt via groups.io <shalopt=
yahoo.com@groups.io> wrote:

"My original idea if I got orders for 10 to 15 of Peter Keller's CRT books
was to have him ship them to me and I would mail them out to the
individuals
who ordered them."
Check out click and ship, pay print label and attach to book, drop off at
the window or have them pick up. But you are doing their work some time it
is cheaper.
gary g








Re: 576 curve tracer transformer

Roy Thistle
 

On Mon, Dec 21, 2020 at 04:51 PM, donald collie wrote:


He`s parting his spares mule out - he might have one
Well if he doesn't have one... he might scrap another 547 for "guitar amp" parts.

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