Agilent/Keysight N2893A Current Probe (Teardown and Repair) - Page 1
Forum section: electronics / testgear

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 03:14:25 pm
content: I just obtained another broken Agilent current probe with a cut wire and repaired it.This one is theAgilent N2893A- 15A Max current- 100 MHz bandwidthThe repair was a success and the probe works now perfectly with my MSO7000B series scope.The repair was easy and straight forward, so I share with you the teardown pictures and repair procedure.This probe does not have a "zero" wheel, instead it is calibrated by the scope's software with the push of a button for "Demag & Calibrate".

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 03:16:42 pm
content: More pictures of the teardown and repair

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 03:18:02 pm
content: Last set of pictures

author: lukier
author_rank: Unknown
timestamp: September 22, 2015, 05:10:10 pm
content: Very nice. I'm also looking for a current probe, but these things, even decades old (I guess) Tek probes hold their prices (except maybe AC only ones), beyond my wallet capabilityI've noticed fair amount of probes with their cable cut on eBay, or sometimes each part listed separately. I suspect this might be intentional, something required by the accounting laws to dispose equipment and write it off the books - horrible practice!

author: dom0
author_rank: Super Contributor
timestamp: September 22, 2015, 05:10:59 pm
content: Now I'm curious what they need the 13600 (OTA) and 675 (power OP) for... any schematics available?

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 05:19:24 pm
content: Quote from: lukier on September 22, 2015, 05:10:10 pmYou are probably right.I was also a little scared that someone might have deliberately killed something inside.It really is a horrible way of getting new equipment for some companies, it seems.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 05:24:11 pm
content: Quote from: dom0 on September 22, 2015, 05:10:59 pmNo, unfortunately there is only a "user guide" and nothing else, not even a calibration guide.Maybe someone here on eevblog has any schematics?Mechanically it is built very well and can be disassembled easily with simple tools.So, it seems it was built for possible repairs.But must likely for internal Agilent repair only.

author: tesla500
author_rank: Regular Contributor
timestamp: September 22, 2015, 05:59:48 pm
content: Quote from: dom0 on September 22, 2015, 05:10:59 pmThe power amp is used as part of the DC bias correction for the current transformer, allowing it to measure DC. I repaired the Tek version of of these probes awhile back, I believe they use the same Japanese made Hall/CT components as the Agilent ones. There's an overview of their operation at 4:55 in the first video below, and a look at the 1979 version of these probes/amps in the second video.Tektronix TCPA300 current probe amplifier debuggingTektronix TCPA300 debugging 2 and a look at an AM503 probe ampAM503 service manualwith schematics

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 08:14:08 pm
content: Quote from: tesla500 on September 22, 2015, 05:59:48 pmThanks for the links to these really interesting videos and service guide.I wish they would still make service guides like in those days.Tomorrow I will do some more test's in the mA range, to see how accurate the Agilent probe is in the lower current ranges

author: I4E
author_rank: Regular Contributor
timestamp: September 22, 2015, 11:54:38 pm
content: Very Interesting!Joy

author: HighVoltage
author_rank: Super Contributor
timestamp: September 23, 2015, 10:05:28 am
content: Ok, now the other side of the scale:Here is a current measurement of a signal current of around 30 mA with a 750 us pulse duration.It seems the Agilent N2893A is well capable of measuring this.The limit of the probe / scope is 20mA / div.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 23, 2015, 10:45:05 am
content: i think you can reuse the cable end black holder. carefully slide out the damaged cord, poke with tweezer etc if necessary, slide in the other undamaged remaining cord and soldered to the probe. appearance back to original with only few cm short of the original cord.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 23, 2015, 08:52:27 pm
content: Hello MechatrommerThat is exactly what I did.The last pictures show the repair and the probe functioning.I just tested the N2893A on my Agilent DSO-X 3034AAnd it also works very well.The probe calibrates itself via software and is really stable at this 1.0 MHz 13 mA RMS signalI took a signal from a Agilent 33522B signal generator and shorted the output.

author: HighVoltage
author_rank: Super Contributor
timestamp: November 22, 2015, 10:30:30 am
content: Quote from: blueskull on November 22, 2015, 10:04:54 amSome companies have the policy to only replace equipment that can not be repaired and then some genius just kills equipment.I have seen it a few times now. I just bought a "dead" scope and all it had was a "removed" cable inside. Probably the same reason.BTW, the current probe works still like a charm after a couple month.

author: lukier
author_rank: Unknown
timestamp: November 22, 2015, 10:31:18 am
content: Quote from: blueskull on November 22, 2015, 10:04:54 amSomething along these lines:https://www.eevblog.com/forum/testgear/abused-test-equipment/https://www.eevblog.com/forum/chat/i-died-a-little-inside-today/

author: lukier
author_rank: Unknown
timestamp: November 22, 2015, 11:34:00 am
content: Quote from: blueskull on November 22, 2015, 10:58:05 amI completely agree. Unfortunately, people don't see destroying/dumping equipment the same way they see throwing away food or burning books.Also, various laws related to his were put in place I suppose, because buying used equipment for 6% of the price or getting it from the dumpster is bad for the economy, doesn't generate as much GDP as buying new stuff all the time.

author: I4E
author_rank: Regular Contributor
timestamp: February 23, 2016, 12:50:38 am
content: I guess it depends on what kind of company you run. If for some reason we got something like that and couldn't sell it to another deal for parts we could atleast write it off as a loss I believe. However having said that I'd never buy something in really rough condition .I know someone who actually went to the dumpster and dug out the unit the company tossed . It was a unit that was easily worth 10K used.Have a good day everyone!Joy

author: radhaz
author_rank: Regular Contributor
timestamp: February 24, 2016, 03:43:04 am
content: Does that board say HIOKI on it?

author: HighVoltage
author_rank: Super Contributor
timestamp: February 25, 2016, 10:07:33 am
content: Quote from: radhaz on February 24, 2016, 03:43:04 amYes, it does, see enclosed picture.Is that the manufacturer or designer of the PCB?You think this was not designed by Agilent?

author: Someone
author_rank: Super Contributor
timestamp: February 25, 2016, 10:04:13 pm
content: Quote from: HighVoltage on February 25, 2016, 10:07:33 amMany probes are rebadged, I only know of two manufacturers of those high performance current probes: Hioki (rebranded by HP/Agilent/Keysight and Lecroy) and Tek.

author: r0d3z1
author_rank: Regular Contributor
timestamp: October 22, 2018, 12:46:10 pm
content: R&S should be the only one big that design its own current probe

author: HighVoltage
author_rank: Super Contributor
timestamp: October 23, 2018, 01:06:04 pm
content: Quote from: r0d3z1 on October 22, 2018, 12:46:10 pmWhich one?All R&S current probes that I have seen at trade shows are Hioki type, looking exactly like Keysight probes.Like in this attachment.They are probably a "little" more expensive than other brands of the same type.

author: r0d3z1
author_rank: Regular Contributor
timestamp: October 23, 2018, 01:55:02 pm
content: QuoteYou are right, they looks like HIOKI.

author: HighVoltage
author_rank: Super Contributor
timestamp: October 23, 2018, 03:00:43 pm
content: Yokogawa also has really nice current probes but they are also only a rebranded Hioki current probe, like this one.I just bought a broken Yokogawa probe and fixed it to like new condition.

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 23, 2018, 03:06:52 pm
content: Quote from: HighVoltage on October 23, 2018, 03:00:43 pmWhat do you measure with this probes, dc, sinusoidal or pulsed currents?Also it did strike me that this models have a fixed scale, I still prefer the old tektronix am503 amplifiers where v/a scale is selectable for both the a6303 and a6302 probes

author: HighVoltage
author_rank: Super Contributor
timestamp: October 23, 2018, 04:27:19 pm
content: Quote from: MasterTech on October 23, 2018, 03:06:52 pmI am measuring mainly fast pulses of current, mostly around zero to 20A-30A and 1 MHz max frequencies.And these Keysight probes are just perfect for that.Yes, the Tektronix amplifiers with selectable scale are good but also sooo expensive.And hard to get cheap in broken and fixable state.