Agilent MSO 5000/6000/7000 - anyone hacked these scopes?

[Gandalf_Sr]

My eBay experience so far trying to buy used Agilent probes is that they either they don't work or, even if they do, the Autoprobe doesn't recognize them properly.  Also, the cost of Agilent probes both new and used seems exorbitant and the fact that the cost of 'repair' is 150% of the cost of a new one (e.g. 1156A) makes me want to go buy Tektronix probes which appear to be awesome engineering and are available for very reasonable cost on eBay e.g. P6245 1.5 GHz active probe available for around $60.

Ironically, Keysight sells the Agilent N2744A T2A adapter for $491 and they CLAIM it fully supports a whole load of different Tek probes including the P6245.  Annoyingly, the two N2744A T2A probe interface adapters on eBay right now are asking $595 and $650 which are both more than the list price.

[Howardlong]

Of the twenty or so Agilent probes I've bought on eBay the only problem with them has been lack of accessories, like ground walking sticks or resistive tips for example. If they're in the eBay picture, unless it states otherwise you are due those parts. But of four active probes (as well as all the passives) I've purchased, all have worked as expected.

I think you've been unlucky, but if the ad states, for example, that the seller couldn't test the probe, then particularly if it's active, all bets are off.

Some things it might be worth a punt on. I bought a 20GHz delay line for an HP sampling scope quite recently, the seller said they couldn't test it, but as all that's in there is a length of transmission line (admittedly made on the thighs of virgin unicorns if the original new selling price is anything to go by) I thought I'd take a punt, and it proved to be fine.

Or maybe I've been lucky of course, but my previous experience of life doesn't refelect that ;-)

[HighVoltage]

At Gandalf_Sr:

I also think you are kind of unlucky.
I have bought many Agilent probes on ebay and usually they worked perfectly.
Some I have bought broken and fixed them.
Like this current probe here that works perfectly with the 7000 series scope:
https://www.eevblog.com/forum/repair/agilent-1147b-current-probe-%282013%29-repair-need-advise/msg748761/#msg748761

I also bought an active probe, the N2795A
Perfect condition in original holster and a very low price
Here are some pictures:

 

[Gandalf_Sr]

Well, it seems my luck has changed   I bought another 'untested' 1156A from eBay for $125 (I know, I'm a chancer) and I kept quiet about it, not wishing to push my luck.

Anyway, it arrived, and at first it didn't seem to work - the scope said it was unsupported - twice! And then it was recognized but the output was stuck at -15 volts   I was about to pull it from the scope in disgust and in doing so, I wiggled the probe to scope connector and the trace went to zero, then I was able to run cal which it passed and I can now see the waveform of the test output as expected

It looks like the Autoprobe scope interfaces are a bit finicky.

The working 1156A didn't come with any accessories but the dud one had everything so now I can combine the good probe with the accessory set and have a fully working 1156A for about $200 which is not bad.  I've also think I've figured out how to connect my dud probe Autoprobe system to the DIY 1GHz MOSFET probe I'm building - my PCBs haven't got here yet.  Can anyone explain how the offset system works from the patent info posted previously?

[Berni]

I have bought some HP 1152A 2.5GHz active probes and out of all 4 there was one that is broken. But it is broken in a very subtle way.

If you put the probe on the good ol front panel probe compensation signal it looks fine, but when i was looking at a PRBS digital signal it seamed to jitter all over the place while it looked fine when using another 1152A. I tried fiddling with pots on it but those only seam to set DC levels and such. The response on quick sharp transitions kinda looks like a passive probe with its compensation out of wack, but here it only shows up on very fast signals. The seller likely had no idea it was broken since it works fine at low frequency.

[Gandalf_Sr]

I have bought some HP 1152A 2.5GHz active probes

Hi Berni, What scope are you using your 1152A probes on?  As long as you didn't pay too much, 3 out of 4 working is OK for eBay.

I made the eBay seller of my working 1156A an offer to buy another one (there are 3 left) at the same price and they turned me down - then sent me a message saying they had done me a favor with the first one as I was a first time buyer. Hmmm, given they are saying it's for parts or not working and returns are not allowed then they can't expect to get working quality prices - eBay is a crap shoot.  I haven't tested my 1156A at 1 GHz yet, I will do that today.

[Berni]

I use those probes on a DSO9204H (That turned itself in to a MSO9404A pretty much) and i love them. But these probes will NOT work on 5000/6000/7000 series scopes(Says unsupported probe and refuses to use it when i tried to plug one in to my MSO6034A) so careful when buying!

A active probe that i got to work on my 6000 series scopes is a Agilent 1134A  InfiniiMax7GHz differential probe since all probes that have the word "InfiniiMax" in the name should work with these scopes. That probe was bought as broken with its case missing but turned out to actually work. A working one runs very expensive on ebay.

However it is possible to make the abundant 1152A probes work on a 6000 scope if you create an adapter that provides external power to the smart probe interface pins as the reason that they don't work is due to the 6000 scopes not being capable of providing enough voltage to them from what i hear. It might be possible to run the probe undervolted or add a boost converter inside the connector as there is a lot of empty space inside. However if you do that you still need to change the EEPROM contents to make it think its a probe it can support.

[Gandalf_Sr]

Berni, Interesting stuff.  Daniel from Keysight who lurks here has stated that the 7000 series has a 'real' Autoprobe interface, not a 'lite' one.  It's possible that the 1152As could work with the IntelliVision series and that all that's stopping that from happening is that Keysight won't tweak their firmware to make it so?
I find it ironic that Keysight sells a $491 N2744A T2A adapter that supports a bunch of Tektronix probes; apparently, when you plug in the N2744A, it comes up with a menu of Tektronix probes and asks you to pick which one you're using with the adapter - they can build that into the scope but not support for many existing Agilent probes.

[Keysight DanielBogdanoff]

Obligatory disclaimer:
Keysight doesn't support modifying, hacking, etc. any firmware or hardware.  Any mods/hacks void warranty and may be illegal.  I'm not a lawyer or saying you should do any of the following.

I played around with an 1152A + 7000B this morning.  The middle pin of the probe (5th one in) is what sets the channel attenuation and impedance.  It pulls out or can be taped over.  By pulling the pin out with some needle nose pliers, I was able to use the 1152A with the 7000B.  I didn't characterize bandwidth performance or anything that rigorous, but I was able to see the expected square wave on the screen.

P.S. of course we lurk a thread titled "anyone hacked these scopes?" 

[TheSteve]

P.S. of course we lurk a thread titled "anyone hacked these scopes?" 

Sheesh, you'd think you guys could figure out how to hack your own scopes without our help 

[HighVoltage]

I played around with an 1152A + 7000B this morning.  The middle pin of the probe (5th one in) is what sets the channel attenuation and impedance.  It pulls out or can be taped over.  By pulling the pin out with some needle nose pliers, I was able to use the 1152A with the 7000B.  I didn't characterize bandwidth performance or anything that rigorous, but I was able to see the expected square wave on the screen.

What a nice support that is, Thank you!

[Keysight DanielBogdanoff]

P.S. of course we lurk a thread titled "anyone hacked these scopes?" 

Sheesh, you'd think you guys could figure out how to hack your own scopes without our help 

Yeah, I'm really looking forward to getting free software options!

[Gandalf_Sr]

Obligatory disclaimer:
Keysight doesn't support modifying, hacking, etc. any firmware or hardware.  Any mods/hacks void warranty and may be illegal.  I'm not a lawyer or saying you should do any of the following.

I played around with an 1152A + 7000B this morning.  The middle pin of the probe (5th one in) is what sets the channel attenuation and impedance.  It pulls out or can be taped over.  By pulling the pin out with some needle nose pliers, I was able to use the 1152A with the 7000B.  I didn't characterize bandwidth performance or anything that rigorous, but I was able to see the expected square wave on the screen.

P.S. of course we lurk a thread titled "anyone hacked these scopes?" 

Daniel, By isolating the ID resistor, you stopped the Autoprobe interface doing the I2C data interrogation of the probe.  So you getting the waveform implies that I was right and that the 1152A can work with the 7000 series - so why isn't it supported in the firmware?  And did you see my earlier post about my 1144A probe which is listed as supported but sets the input impedance to 1 Meg when it should be 50 Ohms?  Can't you get the folks at Keysight to do some improvements on the 7000's Autoprobe interface?  It sure seems like there's room for improvement.

[Howardlong]

I am thinking that any further development on the 6000/7000 is going to be limited, they've probably not long on the shelves.

Well, I was about to turn in after an 18 hour day, glass of wine poured, and read Daniel's note about the 1152A, so I _had_ to try it.

In the meantime, here's an 1152A on a 7104B with a sliver of Kapton tape over the middle pin probing a 54121A TDR output (measured at <33ps rise time). Those brave enough might consider hacking the probe to make it a 50 ohm 10x with the appropriate resistor.

[Keysight DanielBogdanoff]

I am thinking that any further development on the 6000/7000 is going to be limited, they've probably not long on the shelves.

This is more or less correct, it's an old (to us) scope, and we focus development on our newer products.  If someone were to find a critical bug, we'd definitely consider revisiting the firmware.  But, it's a discontinued probe (from the HP days, even). 

I don't know the details of why this probe wasn't included, it's very possible that there's a use case that overloads the autoprobe interface.  I'm 100% certain that compatibility with this probe & scope was considered, but ultimately not included.  I don't know why it ended up this way, but I do know our process here and have a lot of faith in the right decisions being made.  I wouldn't necessarily want to run 4 of these on a signal that pushes the bandwidth and voltage limits of the probe, but it might work fine.    (emoji seems appropriate here)

That being said, the spirit of this blog is pushing the boundaries of equipment, etc. So, I'm willing to post things like this knowing that you all accept the inherent risk of this type of thing.

[mikeselectricstuff]

I'd hope that the probe power supply is sufficiently protected that the worst that would happen is it would cut out or brown out if overloaded rather than letting any smoke out.....

[Berni]

When i get home il try the trick with the 6000 and try to measure what voltages are present on the pins versus plugging it in to the 9000 as well as check the performance of it between the two.

If anyone thinks there is a particular thing i should check in the tests bring it up.

[Gandalf_Sr]

I have looked at the PCB in the Autoprobe (scope) end of my dud 1156A and know which resistor to change - the one that's in there is 46.4k which is the value that, according to US patent on Autoprobe, tells the scope to talk digitally to the probe via I2C. Although I haven't seen the PCB from inside the 1152A, I'd bet a pint or 3 that it's the same PCB because the one in my dud 1156A has components missing e.g. U4 on the bottom side - as an electronics designer, I'd take the same approach, have a single PCB that can be used in multiple products.  Anyway, Table II under column 6 in the patent gives values for the ID resistor that allow you to chose input ratio, impedance, and whether or not offset is used.

The bit I don't fully understand is the offset system - I can see that the scope has the ability to adjust for a volt offset (I think) but is it done during calibration and, if so, where is the calibration stored?  When I power down my 7104B with the 1156A (good one) plugged in and calibrated, it comes back up as calibrated when I power up; remove the probe for 2 seconds and plug it back in and I think it needs recalibrating.

To make the scope work with the 1152A, option 1 would be to swap the ID resistor on the PCB but option 2 would be to decipher the contents of the serial EEPROM that's on the board and then rewrite it to fool the scope into thinking that the 1152A is a different supported probe.  Of course Daniel's right that there are probably reasons why the 1152A was not supported - call me cynical but maybe one was that Agilent wanted to sell more probes?

If you want to go look, I did a tear down thread on the dud 1156A, it turns out that there were broken (blown?) wire bonds on the dead bug IC in the business end of the probe; my pictures also show the PCB in question.

[hs3]

Was the 1152A already a few generations old when the 7000B scopes were introduced? Maybe already discontinued? Maybe they didn't have the parts to make new probes or fix old ones at the time anymore or were running out of existing stock and were not planning to get more. If they would have added support for the probe then it would have created more demand for these probes and getting damaged probes fixed too. But if they didn't have parts for repairing these probes anymore then it would have lead to more disappointed customers when their probe couldn't be fixed. Maybe a bit similar situation to the 1156A probe mentioned here.

Anyway just one though of a slightly different angle to the reasons they might have had. And I'm sure the idea of then selling more new probes doesn't hurt in the decision process either.

[Gandalf_Sr]

HS3, Your suggestions are all possibilities but, given that Autoprobe was already an established standard, wouldn't Agilent want to sell a scope that supported expensive probes that were already out there in large quantities?  Heck, the reason that they made and sold (still sell) the N2744A T2A adapter was so that people who owned Tektronix active probes would be able to buy the 7000B and still use the non-Agilent probes they had paid good money for.

I accept that, now the 7000B is no longer current, this gets to be an exercise in futility - the one I bought from the eBay Keysight store is an Agilent MSO7104B with a little 'Keysight' sticker stuck on the front.

[Berni]

I did some testing on a HP 1152A (Or might have been the Agilent branded one) and here is what i found.

The tape over the middle pin does indeed make it work on my MSO6034A, Just have to manually select 50Ohm and 10:1 mode and off you go. So what is the difference? Turns out that when plugging it in to a DSO9000 makes use of another pin that signals the scope to raise the low voltage supply to +/- 4V while the 6000 series scope appears to be missing this circuitry as that pin is floating, as a result it always supplies +/- 3V on that rail resulting in the probe running on a lower voltage than it was designed for.

So how does this affect the probes performance? I simulated this by covering both the center pin and the pin that signals it it what supply voltage to use on the DSO9000 and did some tests.  Turns out that the 2.5GHz bandwidth of the probe is still there (Not that it matters as those scopes dont go this high) but there is a difference in the probes THD performance at high input voltages. When the probe is running in 'compatibility mode' it slightly distorts signals larger than 12Vpp centered around zero. Also the DC offset feature of the probe is unavailable where the scope feeds back in to the probe a offset voltage that lets the probe look at signals that ride on large DC levels like 20V.

So was Agilent trying to force us in to buying new probes? Looks like no. Its just that the lower end scopes had a cost cutting measure to simplify the circuitry of the autoprobe interface because most likely all the modern probes did not need the low voltage rail to be anything other than 3V.

[hs3]

Ah yes that is indeed one difference. I remember noticing myself that the 1152A asks for 4V supply unlike some other probes that ask for 3V. I remember the 3000 series and probably? other similar newer series scopes only supported 3V. But I thought someone mentioned earlier that the 7000 series should have "full" Autoprobe interface and based on that I thought it would have supported these variable voltages. But I guess the definition of "full" interface might not be so clear.

But if the 7000 series scopes are only able to supply 3V then it's of course clear why probes like 1152A are not supported.

[Keysight DanielBogdanoff]

But I thought someone mentioned earlier that the 7000 series should have "full" Autoprobe interface and based on that I thought it would have supported these variable voltages. But I guess the definition of "full" interface might not be so clear.

So, I did a little digging.  The autoprobe interface can be different for different lines (Infiniium vs InfiniiVision) and for different models (i.e. what year was that scope released?).

So, the 7000s have the "full" autoprobe (aka not "autoprobe lite"), but it isn't necessarily the exact same hardware as other scopes with the autoprobe interface.

[hs3]

I wonder what the main difference between AutoProbe and AutoProbe lite is then? I always thought one significant difference would have been the lack of support for these variable voltages in the lite version. But I admit I have never looked into it closely.

Hmm, I just now decided to have a look if I could find some information about AutoProbe Lite. I found these documents that suggest that the 7000 series might actually have the Lite version?

http://www.alliedelec.com/catalog/catalogpages/201112/1636.pdf
http://www.tevetllc.com/downloads/5989-7650EN.pdf
http://www.testequity.com/documents/pdf/scope-family.pdf

[Keysight DanielBogdanoff]

I wonder what the main difference between AutoProbe and AutoProbe lite is then?

Generally speaking, AutoProbe Lite supports two active probes, AutoProbe supports four. 

This is the general guidance, but it's more of a probe current-draw limitation.