Yet another fast edge pulse generator

[rhb]

I urge that prospective buyers exercise great caution when considering the purchase of one of these pulsers lest you too suffer from uncontrollable TEA.

I just got a Tek 11801 with a pair of SD-22 heads up and running.  And it's all because of the CSA803 plots Leo provides with the units.  Until I saw those plots, I'd never even considered buying a sampling scope.  But after seeing them I *had* to have one.  And I'm now searching for an SD-24 and an S30 or SD-32 to fill the other two slots.

You have been warned. ;-)

[rx8pilot]

I urge that prospective buyers exercise great caution when considering the purchase of one of these pulsers lest you too suffer from uncontrollable TEA.

I just got a Tek 11801 with a pair of SD-22 heads up and running.  And it's all because of the CSA803 plots Leo provides with the units.  Until I saw those plots, I'd never even considered buying a sampling scope.  But after seeing them I *had* to have one.  And I'm now searching for an SD-24 and an S30 or SD-32 to fill the other two slots.

You have been warned. ;-)

Perhaps it should just be called "CAN OF WORMS" or 'PANDORAS BOX"??

[rhb]

I don't yet have a sampling head fast enough for Leo's products,  but I'm pretty sure I'll get one.  Of course, once I have that I'll have to try beating Leo.  That's *highly* unlikely, but trying will certainly be educational.

The value of the education I've gotten from my square wave and impulse generators greatly exceeds the cost.

If you really want to understand electronics  those two devices are the best investment you can make in terms of cost - benefit ratio if you understand the Fourier transform well.

[Berni]

I was looking to get one of those scopes but couldn't find any for a good price. What finally sacred me off them is reading that they can often break and have hard to trace faults that sometimes require replacement of unobtanium parts so a donor unit is needed for spare parts. So yeah that made me scared to buy the cheap "sold as is" listings that i usually go for.

I still have a sampling module for it (I think a SD22) that i got for cheep. But i eventually came across a cheep HP sampling scope and a not too outrageously priced dual channel 20GHz sampling plugin module for it. Works well and is a bit more modern than the Tek, Im still hunting for a 40 GHz plugin module for it, but the going price for those modules is like over 2 or 3 grand on ebay.

[Leo Bodnar]

Half of CSA803/11800 heads that I have bought had some sort of faults - including ones sold as "working". 
Some have lost their EEPROM integrity, which prevents CSA803 from accepting them and the rest had soldering problem.

One had hardline to SUB-D coax internal break.  One had blown termination resistors.  Others just had solder joints that fall apart.  When you try re-soldering the pads, gold is sucked up and leaves awful black coloured unsolderable pads that are repelling solder.

Tek must have gone through rough patch with these heads quality.  Mainframes are not that bad but are full of alien ICs.

Leo

[rhb]

I was *very* lucky.  The 11801 cost $100 + $85 shipping.  It had been in storage in Arizona, so minimal risk of corrosion and the seller furnished a photo of the extended diagnostic screen showing an E5622 (NVRAM) error.  I got two SD-22 heads for $150 delivered and an extension cable for $100 from other sources.

When the 11801 arrived it was DOA and failed the Kernel diagnostics.  I opened it up and after reseating all the boards  in the main card cage and all the connectors I could reach a couple of times it finally booted.

However, at that point I was dead in the water.  Moving the jumpers on the I/O board did not let me get out of the diagnostics.  Then Tom Miller on the TekScopes list suggested I remove the DS1213 "smart sockets" and plug the SRAM directly into the board.  That did the trick, it skipped the self test and worked. When I shifted the jumpers back to the default position, it halted in the Extended Diagnostics with a T1331 error, but now I could exit  by pressing "Exit" twice.  With the E5622 error I could not exit the diagnostics.

When my replacement NVRAM arrived I installed them and after 3 reboots it works like a charm.  At least so far as I can tell.  I still need to read the user manual.

An 11801 that had been stored in a humid climate would require a complete disassembly to address corrosion of the sockets. and cable connectors.  That would be a full day's work.  With no component level data, board swapping is about the only viable repair.  If you can get multiple units for what I paid or boards from a reliable source (e.g. the TekScopes list) they can be maintained.

But this is an issue with all newer instruments.

Leo, were you using 3% silver solder when you ran into the gold soldering problems?  Also what are sensible price ranges for SD-24, SD-30 & SD-32 heads?  Most of the asking prices on eBay are ridiculous.  And then there are sellers who don't allow returns for DOA and are insulted if you offer less than what they are asking.

Fortunately, I don't need any of this,  I just had to have one after getting the pulser plots from you.  So I can wait to get additional heads  at sensible prices.

[Berni]

Now that was a really good bargin.

I had trouble finding then for under 400 bucks, perhaps i just had bad timing. For a 100 bucks i would have taken a risk of buying a potentially dead one and risking that might need to buy another for spare parts.

Then the HP sampling scope showed up for under 100 bucks and went for that, it worked perfectly with zero repairs needed. Tho it appears that a trimm cap for the timebase calibration is kinda wonky, its really touchy and random acting when tweaked, but so far it seams to hold up. Replacing a trimm cap is a easy fix anyway, but if it aint broke don't fix it. Tho come to think of it i don't think i even opened the lid on that scope to see whats inside, i usually like to take a look inside my test gear.

[rhb]

The ringing you see on the step is caused by reflections at the  interfaces of the SMA and 3.5 mm connectors.  I've got two cables like that which are about 0.4 mm difference in length.  I can set cursors on the peaks and read off the difference in the length of the cycle.  However, this is really asking a lot of the SD-22 head as it's near the BW limit of the head.

Really quite amazing.  The sampling is controlled by a 48 bit programmable delay with 20 fs resolution!

These are very much niche instruments.  The asking prices on eBay are generally quite absurd.  But not always.  There's a CSA803 with an SD-46 head for $339.  The SD-46 is a 20 GHz optical to electrical converter so you still need an SD-24 or SD-26 to time your fiber optic line.

[Leo Bodnar]

These are very much niche instruments.  The asking prices on eBay are generally quite absurd.

It's because they have the worst user interface ever designed by man.  It's worse than awful.  I suspect a lot of them are in "like new" condition because engineers did not find half of the functions they needed.

True story: I could not find the way of changing the timebase for more than 40 minutes  and had to resort to reading the operation manual.  It turned out that function buttons on the front panel have state - you need to press them several times to get to the menu you need.  From there it was just a few touchscreen taps (it actually reacts to finger withdrawal), knobs twists, menu presses and numberpad entries away.

Leo

[rhb]

It actually makes the cheap Chinese DSO UIs look good.  I didn't think that was possible.

BTW I've got the calibrator hooked to an SD-22 channel and cursors set at the peaks of the ringing from the mismatch between the 3.5 and SMA connectors.  I've noticed that the waveform moves realtive to the cursors over a period of several minutes.  Any ideas?  I'm wondering if replacing the OXO with one of your GPSDOs would improve the time stability.

[Leo Bodnar]

Both SMA and 2.92mm versions are back in stock. http://www.leobodnar.com/shop/index.php?main_page=index&cPath=124
Thank you for waiting so patiently!
Leo
 

[texaspyro]

I've noticed that the waveform moves realtive to the cursors over a period of several minutes.  Any ideas?  I'm wondering if replacing the OXO with one of your GPSDOs would improve the time stability.

Somewhere back in this thread I posted some measurements and plots of the pulser output timing...

https://www.eevblog.com/forum/projects/yet-another-fast-edge-pulse-generator/msg1404693/#msg1404693

[rhb]

This is not the pulser, I know about that.  You can greatly improve the stability of those by insulating them.  All I've tried so far is glass wool inside heat shrink.  But I need to redo it with larger heat shrink and more glass wool.

This is the calibrator output of the 11801 which has an OXCO, at least I think it is.  I'll open it up and check tomorrow.  I'm currently testing CH 5 & 7 and seeing timing issues. 

I'm going to be pulling it apart tomorrow and reseating cables, etc.  These bays came with plastic covers, so they've probably not been used since it left the factory 30 years ago.  I just bought four SD-26s so I need to get these bays working properly.  Time to put some Dexoit on the connections.

[F6DEX]

Hello

With a just received leobodnar pulser

Keysight DSOX-2022A (200MHz) 1.42ns with the Leo's BNC Inline Terminator 50Ohm,  1.7ns without.
Hameg HM407(40MHz !) : 7ns with, 8.8ns without .

Laurent

[TGyuri]

I've got my pulsar two weeks ago.
I must have to say, it is worth every penny for it.

Dear Leo,
May I ask, do you have hungarian ancestry?

Kind regards,

Gyuri

[Leo Bodnar]

I've got my pulsar two weeks ago. I must have to say, it is worth every penny for it.
...
May I ask, do you have hungarian ancestry?

Thanks, TGyuri. Not that I am aware of!
Leo

[MegaVolt]

I got my pulser !!
Here are the first results. Even a little bit to try TDR.
Scope Tektronix MSO4104B.
 
Interesting how can I change the frequency of his work? How to reduce it? Or make it external? With TDR it turns out to test only fairly short cables

[MegaVolt]

Lecroy sda 820Zi:
3,5 GHz (BNC) input
20 GHz (sma) input (pulser+BNC-SMA connector)

[Converter]

MegaVolt, sorry, but what was it now?
What kind of fabulous sma adapter did you use (homemade)?
Why did you use the cursor measurements in manual mode?
Equivalent mode is also preferred when you have a repeating signal.

[MegaVolt]

MegaVolt, sorry, but what was it now?
What kind of fabulous sma adapter did you use?

https://aliexpress.com/item/32831271535.html

And uto prevented you from applying the automatic measurement mode Rise time (10-90), instead of moving the cursors with your hands anywhere?

The screenshots have both methods of measurement. Automatic and manual.

And between them there are some differences. I think this is due to the fact that the signal is not a perfect rectangle. And for this, the automation does not quite correctly set the thresholds of 10% and 90% and get a slightly better time.

[Converter]

MegaVolt, sorry, but what was it now?
What kind of fabulous sma adapter did you use?

https://aliexpress.com/item/32831271535.html

Something went wrong in your lab. From an oscilloscope with a bandwidth of 20 GHz, one should have expected something better.

[Berni]

Yeah a 20GHz scope should be getting somewhere around 50ps rise times out of it. The odd uneven rise time could hint at some impedance mismatch or connector issue. What sort of connectors does that scope have anyway?

And yeah id suggest using equivalent time sampling with some averaging on top to get a better look at the waveform.

[Leo Bodnar]

Your screen captures show about 1.2V signal amplitude. 
Try reducing it to 700-900mV.  Higher amplitude increases edge rise time on this particular pulser.
Leo

The screenshots have both methods of measurement. Automatic and manual.

And between them there are some differences. I think this is due to the fact that the signal is not a perfect rectangle. And for this, the automation does not quite correctly set the thresholds of 10% and 90% and get a slightly better time.

[2N3055]

For a 3.5 GHz scope with BNC/SMA  converter about 150 something psec sounds fine to me ..
It is 20GHz bandwidth scope but on ProLink inputs. He used ProBus input, that one has 3.5 GHz bandwidth...

[Converter]

For a 3.5 GHz scope with BNC/SMA  converter about 150 something psec sounds fine to me ..
It is 20GHz bandwidth scope but on ProLink inputs. He used ProBus input, that one has 3.5 GHz bandwidth...

No, as far as I understood his message, in the last 2 screenshots he used the HF-input ProLink with the appropriate adapter.
If it is not, let him correct.