To be honest, I'm very exciting since this is my 1st diff probe, appreciate any suggestions or comments on this almost 40 years old probe
Hmm.... Five minutes, I'll crack open mine and let you know.
Yep, here's mine, connected for 120V. Looks like two windings in parallel. I'm sure they can be put in series.
Say a few prayers to your deity of choice that it's still accurate. Damn thing has more trimmers than Carter's got pills. (Shit, I think I see two right there in the PSU block that I never noticed before.... |O)
These can also have some funny weird problems that don't always show up, so check it over completely before trusting anything it says. Mine would pick up a parasitic oscillation on just one setting. No idea what caused that - it went away after I pulled it apart, saw nothing wrong and put it back together...
It supports up to 250V with the 10x head and 25V with the 1x head. :box:
btw it cost me < 40 US bucks (excl s/h), not a terrible deal, right ?
Mind elaborate further details ? What weird problems ? Also which setting and/or condition was that on the parasitic oscillation ?
Pulled apart on which part ? Probe's body ? Amplifier ? or the PSU unit ?
It's not that scary. It's not quite a lump of voodoo and fairy dust requiring $100,000 of equipment to calibrate - just a massive pain in the ass. Dedicate a day or two to it if it needs work.
The oscillation, if I remember correctly, was on 20 mV/div, regardless of AC/DC coupling. Close to a sine, >100MHz or so, about half a division ptp. I took apart the amplifier box and it was fixed.
Mine hadn't drifted at all since its last calibration in 1989, so if it works I doubt you'll have any trouble. (I'd take apart the probe again to see where the problem resistor was, but I'm not sure I want to go opening it. It was just a mechanical fault - lead snapped - so I doubt there's any reason for you to suspect it will fail there.) The one I had to repair and calibrate was a different one that I got in non-working condition.
Just a quick hint/warning if you do end up having to poke around in it, though I'm sure you know: low voltage hadn't been discovered yet in the '60s.... It does have a rail around 100V or so. So don't go licking it or prodding around with sausage-fingers ;D
I am not sure about this particular probe, but to calibrate Agilent 1141A you only need DC source, DMM, BNC to banana connector and BNC Tee. And I don't bother most of the time cuz for digital signals it does not really matter.
One thing you may need is a good 50ohm feed through terminator for your oscilloscope because probe output is 50 ohm and oscilloscope is hi-Z. Without terminator signal on scope won't make any sense.
Does anyone have a service manual which include the schematic.
Does anyone have a service manual which include the schematic.Note that there are two different versions (what do you expect if a product is available for decades?) with different manuals. I believe the S/N cutoffs were up to S/N B0199999 for the early version and from version S/N B030100 (or B032108?) for the late version.
It's not that scary. It's not quite a lump of voodoo and fairy dust requiring $100,000 of equipment to calibrate - just a massive pain in the ass. Dedicate a day or two to it if it needs work.
I'm assuming you have some sort of precision signal generator ? If you don't mind explain what you did.
i believe calibration is pretty easy once you know where to twist. since its not meant for high accuracy such as 11 digit DMM or so. if i am you, all i need to do is to make the P6046 read exactly as an oscilloscope does with normal Hi-Z probe. FG output to one diff probe input, let say +ve input. and then -ve input to FG's gnd, thats good enough for me. CMRR which is the single most important aspect of diff probe is even easier to calibrate, both +ve and -ve input probing at the same point, ie FG's output and twist internal trimpots or trimcaps until smallest ripple output. YMMV.Do you disagree with Jim Williams's statement? How many have you calibrated? Why do you think they made a special calibration shield to provide shielding during calibration? The circuit is extremely sensitive to interference that may show up as differential mode noise. And in general adjusting a large number of interacting trimmers takes forever. Especially with fun statements like 'if these trimmers need more than a little adjustment, go back to step X'.
I did. You "need" a square wave generator with rise time under 1ns, which I couldn't find anywhere.The Tek PG502, PG503 and PG506 occasionally show up on the used market for affordable prices. All can generate pulses with <= 1 ns rise time. I believe the PG506 was specified in the late version manual. Downside is that they need a TM500 mainframe, and affordable is still going to be more than $40. For good transient response the pulse needs to be clean, that may be tricky in a DIY generator.
You might not really need that, though, I just kind of wanted to build one. The calibration instructions say <1ns rise, but the rise time of the instrument itself is specified as 3.5ns, which you should be able to easily achieve with a fast 7400 logic family like 74AC. Whether that's good enough for calibration would require a careful reading of the instructions, though...The total rise time of the system is the root of the sum of squares of the rise time of the components. So a 3.5 ns square wave through a 3.5 ns probe + scope would show up as a 5 ns signal on the scope. The contribution of a 1 ns to the rise time is negligible, giving an almost 3.5 ns rise time. My guess is that they want the signal to be much faster than the probe.
You also need a function generator capable of predictable amplitude up to 50 MHz. I usually use my HP 3325A for this sort of thing, but its precision-amplitude output only goes to 20 MHz. I asked very, very nicely if I could use one of the function generators in my school's lab for this ;D - can't remember what they are - fairly pedestrian, but modern, DDS generators with a maximum of 50 MHz. The manual doesn't specify how precise the amplitude must be, unless I missed it, but at frequencies over 1 MHz I doubt they're looking for too high an amplitude precision, otherwise you start having to worry about things like insertion loss of the cable too!It's probably only critical for the bandwidth check, for which they suggest a leveled sine generator (doesn't have to be accurate, just constant across the bandwidth). But bandwidth is only a check. If you determine that it only has 80 MHz bandwidth, what are you going to do? In my opinion you can easily skip this step as long as the transient response looks reasonable.
I did. You "need" a square wave generator with rise time under 1ns, which I couldn't find anywhere.The Tek PG502, PG503 and PG506 occasionally show up on the used market for affordable prices. All can generate pulses with <= 1 ns rise time. I believe the PG506 was specified in the late version manual. Downside is that they need a TM500 mainframe, and affordable is still going to be more than $40. For good transient response the pulse needs to be clean, that may be tricky in a DIY generator. Especially with fun statements like 'if these trimmers need more than a little adjustment, go back to step X'.
1141A is actually is pretty ancient too. I just followed user/service manual. Have you found a manual for yours? Manual should explain everything in details.I am not sure about this particular probe, but to calibrate Agilent 1141A you only need DC source, DMM, BNC to banana connector and BNC Tee. And I don't bother most of the time cuz for digital signals it does not really matter.
Really, sounds so simple & easy. :o
But again, this "vintage probe" is not the same league as that modern Agilent 1141A.
Note that there are two different versions (what do you expect if a product is available for decades?) with different manuals. I believe the S/N cutoffs were up to S/N B0199999 for the early version and from version S/N B030100 (or B032108?) for the late version.Models cut off at S/N B032108 , according to this web site -> The P6046 Differential Probe (http://www.i9t.net/p6046/p6046.html)
Two (paid) sources that provide excellent scans:
Artek Manuals: both late and early version available (http://artekmanuals.com/manuals/tektronix-manuals/)
Qservice: only late version (http://www.qservice.tv/vpasp/shopexd.asp?id=1589&bc=no)
Note that there are two different versions (what do you expect if a product is available for decades?) with different manuals.
Say a few prayers to your deity of choice that it's still accurate. Damn thing has more trimmers than Carter's got pills. (Shit, I think I see two right there in the PSU block that I never noticed before.... |O)
Alm, about that the two versions, do you have any link/reference on it ? My Google-fu fails me.This page (http://www.i9t.net/p6046/p6046.html) briefly mentions it, and links to a document describing the differences between the manuals, but this link is broken. No functional changes as far as I know, but enough part substitutions to prompt the creation of a new manual, plus a different calibration procedure with newer equipment (PG506/SG503 as opposed to the Tek 1xx series sine / pulse generators).
Did you mean these 4 covered holes at the probe's body ? Just realized it after looking them both closely.Those four trimmers are just four of the trimmers inside the probe. The calibration shield I was referring to has more holes, a picture is posted on the site I already linked to (http://www.i9t.net/p6046/p6046.html). The four trimmers are the ones that might need adjustment within the calibration period of 1 year to maintain its aggressive CMRR specs. A full calibration more trimmers in both the probe and the amplifier. You also need a shielded box with connector for both probe tips, also shown on that page, to feed an identical signal to both tips(note that you're adjusting for 10,000:1 CMRR!). I wouldn't bother with adjustments as long as it performs decently.
From the net, probe body with trimmer holes.
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While mine doesn't have it. :-\
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Aw, shit, your probe doesn't have the cover with adjustment holes? Hopefully it's still good, because you're going to have one hell of a time making adjustments. I suggest cutting and drilling a shield to match. It is very susceptible to noise, you really can't just take off the cover and adjust it that way.Yeah, all I can do is pray now, btw its still on its way though and I might wait for weeks before it arrived. ???
But as I said before, if it was good, it probably is good. It's had a long time to settle between manufacture and whenever the last calibration was, it probably hasn't drifted much since.
This page (http://www.i9t.net/p6046/p6046.html) briefly mentions it, and links to a document describing the differences between the manuals, but this link is broken. No functional changes as far as I know, but enough part substitutions to prompt the creation of a new manual, plus a different calibration procedure with newer equipment (PG506/SG503 as opposed to the Tek 1xx series sine / pulse generators).Yep, that was my problem, but after spending for hours at Tek scopes Yahoo mail-list, reading those "ancient" posts :-[, and with much better & improved Google-Fu, finally I spotted the P6046 manuals revisions document, attached below in this post the document as "P6046CHT.PDF".
Those four trimmers are just four of the trimmers inside the probe. The calibration shield I was referring to has more holes, a picture is posted on the site I already linked to (http://www.i9t.net/p6046/p6046.html). The four trimmers are the ones that might need adjustment within the calibration period of 1 year to maintain its aggressive CMRR specs. A full calibration more trimmers in both the probe and the amplifier. You also need a shielded box with connector for both probe tips, also shown on that page, to feed an identical signal to both tips(note that you're adjusting for 10,000:1 CMRR!). I wouldn't bother with adjustments as long as it performs decently.As a hobbyist, I don't have enough tools like a pro, so targeting to adjust it especially that cool CMRR at 10,000:1 is not realistic for me, and also I guess my Tek 2901 time mark generator won't help either, cause its just for scopes horizontal adjustment, am I right ?. :-//
There are some accessories that might be nice to get. From the factory it shipped with shorting caps across the tips, since the input FET is quite sensitive. You can fabricate something yourself with something like alufoil. It also came with a 10x attenuator that extended its voltage range, at the cost of CMRR. Swivel tips allows you to vary the spacing between the tips. The other accessories are less important in my opinion.If you see the probe's images gallery, I guess it came without all those swivel tips and other standard accessories, only the 10X head.
As a hobbyist, I don't have enough tools like a pro, so targeting to adjust it especially that cool CMRR at 10,000:1 is not realistic for me, and also I guess my Tek 2901 time mark generator won't help either, cause its just for scopes horizontal adjustment, am I right ?. :-//Not for bandwidth or transient response.
Alm, any hint how can I spot if the probe's accuracy or it's CMRR is drifted way too much ? I mean sort of quick and dirty method to verify it ? Fyi, I don't have any wave generator, let alone the precision one. :'(Try the common mode test described in the manual: feed a common signal to both probe tips (try to keep the signal paths the same and grounds short, i.e. use the grounding collar with some wire wrapped around it). Then observe the amplitude of the signal relative to the amplitude you measure in single ended mode (connect only one probe tip to the signal, short the other to its grounding collar). Amplitude is not critical as long as it's stable. Frequency content is somewhat relevant since CMRR is a function of frequency. Non-sinusoidal signals might make the results harder to interpret, although FFT (assuming you're using a DSO) might be helpful. The probe cal signal (for low frequency) and sine waves from the 2901 (high frequencies) might be used as test signals.
Is it easy to build/fabricate those accessories ? Appreciate if you could share high resolution photos of those for this P6046 probe, and to c4757p too if this is not troubling you too much.Here is a picture of the swivel tips (http://qservice.tv/vpasp/shopexd.asp?id=11818&bc=no). Shouldn't be too hard as long as you can devise a reliable way of connecting to the probe tip without introducing excessive inductance (no alligator clips and long leads :P). A machine pin as used in a high quality DIP socket might work. The manual contains a drawing of each of the accessories, let me know if you need a picture of something specific.
The probe cal signal (for low frequency) and sine waves from the 2901 (high frequencies) might be used as test signals.Do you mean compare the 2901 (high freq sin) with the reading from the scope when it was attached directly ? Also where to probe (using this P6046), directly at the 2901 BNC output ?
Here is a picture of the swivel tips (http://qservice.tv/vpasp/shopexd.asp?id=11818&bc=no). Shouldn't be too hard as long as you can devise a reliable way of connecting to the probe tip without introducing excessive inductance (no alligator clips and long leads :P). A machine pin as used in a high quality DIP socket might work. The manual contains a drawing of each of the accessories, let me know if you need a picture of something specific.So that swivel tips are most useful right ? Looks easy enough to build it from machine pins. :-+
Do you mean compare the 2901 (high freq sin) with the reading from the scope when it was attached directly ? Also where to probe (using this P6046), directly at the 2901 BNC output ?You want to feed a signal with a know amplitude (how you measure doesn't really matter) to both probe tips, so it's a common mode signal. It should reject this common mode signal, and the ratio between the amplitude of this signal from the P6046 (taking into account attenuation) and directly measured (with another probe or with the P6046 in single-ended mode) is the CMRR. Ideally you would used the fixture pictured here (http://www.i9t.net/p6046/p6046.html), but lacking that, I would probably bring the signal to a PCB with two parallel traces for signal and ground, put the two probe tips on the signal trace and use some improvised ground springs that go around both grounding collars for the ground connection. You want as little as possible difference in length and inductance between the two tips and you want to reduce the loop area between the tips, since that would allow inductive pickup of differential mode signals. Any differential mode signals you pick up will reduce the apparent CMRR, and if you're looking for 10k:1 or 1k:1 CMRR, then even a tiny amount of differential mode signal can swamp the residual common mode signal. You can basically follow the manual for this, you just have to improvise the connections and signal sources. I believe you set the scope to a fairly high sensitivity in AC coupling mode, but check the manual for that.
So that swivel tips are most useful right ? Looks easy enough to build it from machine pins. :-+The ground lead is not useless, what I was alluding to was that jumper leads are not a replacement for the swivel tips. You want as little loop area and inductance as possible, so you the length should be say an inch, not a foot.
Its still on it's way, so I mightbugask ^-^ you again once its arrived and had the chance to test it myself.
Also I found few photos (attached below) on the net for the accessories, I can see there is a long lead with alligator clip (at 2nd pic), is that the one you mentioned that is useless ? Also 50 Ohm terminator ? I assume thats for scope without 50R termination. Also I'm curious, what is that yellow stick (2nd pic) ?
I just use a 230-110 transformer. That is permanent on my desk because I have more 115V gear.It's trivial to rewire the transformer for 230 V if you ever feel the need to.
The amplifier is designed to work with the scope set to 10 mV/div, this is when the attenuation factors on the amplifier are accurate. The amplifier is only specified for a dynamic range of +/- 100 mVi'm not sure i understand
, so going to lower vertical sensitivities of the scope has limited use. Not sure how much higher it goes, not much I suspect. Higher sensitivities are limited by noise. So in general you don't touch the vertical controls of the scope. This also saves you from doing mental arithmetic with attenuation factors.i'm not sure i understand sorry
The output from a 1Vp-p sine at 200 mV/div will be a 50 mVp-p sine, so setting the scope to 1 V/div will result in a very compressed sine.i'm trying to get mental arithmetic for this... so from what i gather in your post... if i set the amplifier at X (mV/div,) the probe output will be Y (Vp-p) sine? please confirm if i have mistake (below)...
I would probably keep the attenuator tip on until you've fashioned some sort of shorting caps. That should give atleast some ESD protection. The input FET is quite sensitive, more so than single-ended FET probes, since any ESD protection diode or resistor would degrade the CMRR. And of course Tek in their infinite wisdom decided to use polystyrene packaging.
Condition looks fine. Don't forget to change the fuse when you change the voltage taps. At least they didn't use the terrible trick they used for the 134 where they put a resistor in series with an overheating 110 V transformer.
This is npot so easy as it sounds because it has a USA connector and that is not easy to swap for a dutch plug.
Convert it to 230 V, put a big label on it, and use a travel adapter to plug it into your local mains socket. Of course there's nothing wrong with using it at 110 V if you have that available.
Shorting caps ? How ? Please elaborate further, and I'm assuming shorting from the tip to the ground right ?Yep, just short the probe tip to the grounding sleeve. To quote myself from earlier in this thread:
From the factory it shipped with shorting caps across the tips, since the input FET is quite sensitive. You can fabricate something yourself with something like alufoil.
Apart from Fred (PA4TIM), appreciate if any one of you willing to help me on this too. Calling out c4757p ... :)I attached some pictures, let me know if you need more. I included one of each of the accessories, but I figured you knew what a ground lead, a BNC cable and a terminator looks like. You should be able to identify them from drawings in the manual.
I attached some pictures, let me know if you need more. I included one of each of the accessories, but I figured you knew what a ground lead, a BNC cable and a terminator looks like. You should be able to identify them from drawings in the manual.
The close-ups are the tip of the swivel tip, the probe socket part of the swivel tip, the socket part of the hooks (which is fairly similar to the swivel tip and could be converted in one) and the inside of a shorting cap. The shorting cap consists of two strips of springy metal that contact the grounding sleeve and meet at the tip. The tip would go through the slit between the two strips that you can barely see in this picture.
teardown of the attenuators will be nice.
Btw, the attenuator doesn't have any sensitive JFET in it right ?I haven't seen a schematic or opened mine up, but since the thing has no power supply, I consider it highly unlikely. Probably just a compensated voltage divider with a passive compensation network and some extra attention paid to matching the two channels. The CMRR with attenuator is specified as 'only' 1000:1, but that still requires better than 0.1% matching of the attenuation ratio across the bandwidth of the probe.
What is that yellow metal thing in the middle , the black cap below the grey shorting cap used for ? and also the silvery bnc connector like that in the plastic bag ? Is that for custom diy tip ?The manual calls the gold-colored one a spring ground clip. It clips on the ground sleeve, somewhat similar to the low-inductance ground springs you have with single-ended passive probes. The connector in the plastic bag is what the manual calls test jack, a coaxial socket that fits one of the probe tips and that can be used to provide a coaxial connection to some custom circuit.
So what are those black caps that those I have are used for ? Especially with the exposed tiny part of the tip ? The manual really doesn't tell much about the detail usage for those accessories. :-//The black ones (in my picture) just insulate the ground sleeve to prevent it from touching anything in the circuit. The ones that are dark gray in my picture are IC insulator tips that are designed for probing DIP ICs (or anything with similar lead spacing): it prevents the tip from shorting two adjacent pins and stabilizes it when probing DIP ICs.
i dont care, teardown of an attenuator of any kind will always be fun. :Pteardown of the attenuators will be nice.Yes, thats the plan, but design wise, I don't think it will compatible with your HP probe.
The CMRR with attenuator is specified as 'only' 1000:1, but that still requires better than 0.1% matching of the attenuation ratio across the bandwidth of the probe.
The connector in the plastic bag is what the manual calls test jack, a coaxial socket that fits one of the probe tips and that can be used to provide a coaxial connection to some custom circuit.
The ones that are dark gray in my picture are IC insulator tips that are designed for probing DIP ICs (or anything with similar lead spacing): it prevents the tip from shorting two adjacent pins and stabilizes it when probing DIP ICs.
The CMRR with attenuator is specified as 'only' 1000:1, but that still requires better than 0.1% matching of the attenuation ratio across the bandwidth of the probe.
Btw, does the 1000:1 performance at this vintage probe is still considered a decent performer compared to modern probe with comparable bandwidth ?
It is more like 500:1 at 50 MHz but that is still cutting edge performance. 500:1 is 54 dB. Good high voltage differential probes are only 30 dB at 50 MHz and the best ones are only about 45dB. The best low voltage differential probes I could find only match the P6046 at about 55 dB at 50 MHz but have much higher bandwidths.David, thanks, its good to know that even a 50 years old design still can stand through time.
The P6046 was in production for a long time.
Hey BravoV, have you been able to rewire the PSU for 230 V? I am just shopping for a set on fleebay which a collegue of mine will than take here from the US. (Shipping to Europe costs usually almost as the set itself) After it gets here I could also use a direct 230V input instead off using transformer ;-)
Anyway, this should be correct, right? Shematic says bridge between 2 and 3 instead of 1 to 2 and 3 to 4
- do i need to connect the earth terminal? I don't have an US to IT/SHUCKO adapter with earth at the moment
-can i change the plug? Though the power supply is bulky, i'd rather build an adapter cable
-if i wanted to probe between two points at an arbitrary distance... what are the two wire thingie that you can plug on the tip called? Where can i find them?