Agilent 34410A, Repair of 2 dead meters [success] - Page 1
Forum section: electronics / repair

author: HighVoltage
author_rank: Super Contributor
timestamp: December 12, 2015, 02:36:57 pm
content: I am starting this thread at the beginning of the repair of 2 dead meters.Both areAGILENT 34410ABoth units show garbage on the screen, like total nonsense values in any mode.But they were cheap as a pair and I would be happy to get one good one out of the two, but I am aiming to repair both.The first unit seems to be complete after taking it apart.,The second one has a missing Rear/Front switch and a missing relay.I ordered a switch and relaySwitch part number:51902 (F8UEE), 8PDT PUSH-PUSH UNSLDRelay part number:G6AK-274P-STLT-US-DC5This is my first serious repair of a 34410A. So far, I have only repaired plenty of 34401A meters but never a 34410AThe good thing is, that the Service Manual and the Schematics are available for download.But since this meter is very different from the 34401A, the repair job might be different as well.Does anyone here have experience in repairing the 34410A?Full schematic:http://www.keysight.com/owc_discussions/thread.jspa?threadID=36971&tstart=-1

author: HighVoltage
author_rank: Super Contributor
timestamp: December 12, 2015, 02:48:49 pm
content: PLESA posted a picture of a 34410A main board in his upgrade thread.https://www.eevblog.com/forum/testgear/possible-upgrade-agilent-34410a-to-34411a/msg814698/#msg814698Interestingly, his board has the typical green PCB color.The main boards in both of my units are much darker.Also, why is R3121 not populated?May be only in the 34411A?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: December 12, 2015, 03:07:53 pm
content: Hi,The schematic shows two shunt resistors in parallel R213 and R2131. R2131 is marked 'never load'. It is probably allows them to use two different kinds of resistors that don't have the same footprint.Regards,Jay_Diddy_B

author: jitter
author_rank: Frequent Contributor
timestamp: December 12, 2015, 03:10:41 pm
content: Quote from: HighVoltage on December 12, 2015, 02:48:49 pmColour variations between pcbs are very normal and are not indicative of anything other than usual variations in processing.Usually pcbs are manufactured in batches not too long before they're needed. Bare pcbs are not as durable as one might think. Solderability may only be guaranteed by the manufacturer for a year or so when stored in good conditions (vacuum sealed packaging and with a bag of dessicant).Older pcbs, or those exposed to air must be baked before stuffing and soldering. Even older pcbs might not be solderable anymore without them getting a special treatment which I believe isn't very cheap.Every batch can turn out slightly different in colour. And switching between manufacturers (most of which are in China) goes on all the time, even though the people selling them to you remain the same. I don't know how many times I've seen pcbs change from matt green to glossy green and back again...Usually there will be a datecode somewhere on the pcb. Often you can also find the logo of the actual pcb-manufacturer rather than the brand of the product (unless they're specifically instructed to leave those off).

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 12, 2015, 04:36:19 pm
content: Quote from: HighVoltage on December 12, 2015, 02:36:57 pmHmm, I hope this is not what I think: More defects and used as a parts donor....

author: HighVoltage
author_rank: Super Contributor
timestamp: December 12, 2015, 05:24:30 pm
content: Thanks for the feedbackI do have a 34410A in good working condition, so I can take some measurements if needed.There was so much dirt in both of these used units, there is a possibility that the dirt was part of the problem, creating some lower resistance on the PCB. So I took both main boards and gave them a good cleaning in alcohol.Quote from: PA0PBZ on December 12, 2015, 04:36:19 pmYes, it is a possibility.But why would someone take a relay out as a donor part?I will only be able to tell, after installing a new switch and relay.The lever for the rear/front switch is also missing, but it is available from Keysight as a replacement part.(Hopefully it is still available for sale)In general, I can not believe how badly some people treat their equipment.But then, they might not even know the value of such precision instrument.

author: TheSteve
author_rank: Unknown
timestamp: December 12, 2015, 05:49:11 pm
content: Are they actually functioning but just have a scrambled display, is the any com via the gpib port?

author: HighVoltage
author_rank: Super Contributor
timestamp: December 12, 2015, 08:11:40 pm
content: Quote from: TheSteve on December 12, 2015, 05:49:11 pmThe displays where updating with very unstable readings but even the one without the relay and missing switch had some numbers on the display.They just did not make any sense.For instance, in VDC mode it showed values around 1 VDC but constantly changingI now cleaned the boards complete and will let them sit over night.Tomorrow I will make an attempt to re-assemble the fist unit and take some measurementsBTW, it was nasty sticky stuff on the PCB, no idea in what environment they have been used.But everything came off very well with cleaning alcohol.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 12, 2015, 09:21:42 pm
content: A first step would be checking for damaged electrolytic caps in the supply area. Only than power tham up and check the internal supply voltages.If the display is showing numbers, this allready quite a good sign - so display part seems to work.The internal selftest may help a lot.

author: MadTux
author_rank: Frequent Contributor
timestamp: December 12, 2015, 11:46:41 pm
content: As already mentioned, check the voltages first. Then check if the relays at the input work. Apart from that, it's crazy how few and custom made parts are in there compared to older DMMs like 3456/3457 or Keithley 2015. One PLCC at the input, one FPGA probably as ADC controller and BGA microcontroller with custom Agilent part number. Any one of these is dead, not much you can do, except for the FPGA. Also, BGA soldering is not fun.

author: Macbeth
author_rank: Super Contributor
timestamp: December 12, 2015, 11:59:18 pm
content: Quote from: MadTux on December 12, 2015, 11:46:41 pmThats a good thing, surely? Less custom parts the better.QuoteBGA is a doddle, just ask Louis Rossman.What is a fair price for a used/may need some repair 34410A? They do seem a bit nicer than the 34401A's...

author: MadTux
author_rank: Frequent Contributor
timestamp: December 13, 2015, 12:07:35 am
content: I was maybe a bit unclear, very few and nearly all custom Agilent made parts in thereIn old 3456/3457, it was only the reference resistor/voltage divider arrays that could go bad, but I never had one go bad. Also not too difficult to replace with discrete components. All digital stuff is complete off the shelf.Here, basically 3 custom HP parts do all the magic. Repair nightmare, without parts unit

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 12:31:19 am
content: Quote from: Macbeth on December 12, 2015, 11:59:18 pmOriginally it was Euro 450 for one unit that was supposedly working perfectly and a free broken unit on top.When both arrived from the seller and both were kind of dead and one had missing parts, I got a good refund.Now I have two broken units for a total of Euro 250It will be a total waste if they will not come back to lifeIt will be a steal if only one will work at the endGood units go for around Euro 600 these days, so about twice as much as a 34401A.

author: TheSteve
author_rank: Unknown
timestamp: December 13, 2015, 12:58:43 am
content: I'm looking forward to seeing how this progresses. With TiN no longer working daily on his 3458A we need a good DMM repair thread

author: Macbeth
author_rank: Super Contributor
timestamp: December 13, 2015, 01:04:28 am
content: Quote from: MadTux on December 13, 2015, 12:07:35 amOnly if unobtanium, much like TiNs 3458A ASICs. Or else deliberately priced way beyond reasonable.This "throw away" thing is something I really hate. Ok, when a replacement consumer TV costs less than a service engineers hourly wages then fair enough, though in my own case when my cheap shit fails I still persist on fixing it. Professionally I got out of that game decades ago and switched to IT.But expensive test equipment? Or as Louis Rossman fixes, expensive Apple consumer equipment. There is no reason it should be beyond economical repair. Yes, component level repair not board swapping.Go back to the 80's and earlier and you would find a service manual for everything. Really nice ones too - fold out sheets, transparent overlays, fully indexed. We don't need that anymore - we have the web. There is literally no cost in publishing this stuff anymore. Just a grim culture of keeping hold of it all.If the RoHS and global warming advocates want to do something then they should force manufacturers to release service data and provide parts or alternative part numbers. Much better than filling up landfill. Bah!

author: lukier
author_rank: Unknown
timestamp: December 13, 2015, 01:15:41 am
content: Quote from: 3roomlab on December 13, 2015, 12:22:02 amI believe 34410A/11A use Multi-Slope IV ADC, the same as the latest generation of 3446xA/34470A. From what I understand the 12 bit ADC (called FINE ADC) is used in a similar manner to the previous generation (34401A) - to read the residual charge at the end of the conversion. The much faster 8 bit ADC (COARSE ADC) is used instead of a zero crossing comparator. Maybe this provides more accurate zero crossing detection.There are also some differences in the current steering part, instead of traditional resistor network and switches for various slopes it seems to use some form of PWM DAC (AD_PWM to DAM_OUT signal) that generates current for the integrator.That's what I thought at least after quick look at the schematics and Dave's 34461A teardown. It would be great if someone with much more ADC expertise could shed more light on the Multi-Slope IV architecture, what benefits the 8 bit ADC gives over comparator, is PWM DAC better in terms of injected noise than resistors + analog switches, how good this ADC scheme is and how far from 3458A INL/DNL?

author: Macbeth
author_rank: Super Contributor
timestamp: December 13, 2015, 01:28:28 am
content: Quote from: 3roomlab on December 13, 2015, 01:11:15 amIndeed. But a modern young pup fixing old stuff and relying on those test point volts has to bear in mind they were taken with a 20Kohm/volt meter like an AVO 8, even well into the early '90s when we would all be DMMs with 10Mohm impedance.

author: bingo600
author_rank: Super Contributor
timestamp: December 13, 2015, 07:46:32 am
content: Quote from: lukier on December 13, 2015, 01:15:41 amThere's some Multislope info in this HP Journal pg. 17 , (it's for the 3457A , so it might be from an older type ADC)http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1986-02.pdf/Bingo

author: Gyro
author_rank: Super Contributor
timestamp: December 13, 2015, 11:06:42 am
content: QuoteCouldn't that just be it operating with a floating input? Particularly the one with the missing front-back switch and relay.

author: plesa
author_rank: Frequent Contributor
timestamp: December 13, 2015, 11:38:30 am
content: Quote from: HighVoltage on December 12, 2015, 02:48:49 pmR3121 is also not populated in 34411A. Your black PCB looks to me like dark greenAnd the picture are borrowed from internet, because I do not want to remove boards from chassis.Pictures are from this site, where you can find internals of L4411A, which is different layout of 34411A.http://letsdisassembleit.com/news.php?extend.4Also the 34410A is therehttp://letsdisassembleit.com/news.php?extend.2The price of used 34410A should be between 400-600 USD. Not working 100-150 USD.I posted few days ago big auction where was lot o K2001 and 34410A for such price.https://www.eevblog.com/forum/buysellwanted/lot-of-keithley-2001-agilent-34410a-and-other-equipment/msg818608/#msg818608Today I'm going to check the debug output in 4411A to check the differences between 34410A and 34411A.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 13, 2015, 11:59:07 am
content: Quote from: plesa on December 13, 2015, 11:38:30 amYou should really fix your 'F' key

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 12:42:33 pm
content: The main board is clean now and all the sticky stuff has been removed by the alcohol washing.This is the board with the switch and relay in place.I measured all the gold switch elements and find measurements of 3 mOhm to 9 mOhm on all contactsI would assume that this is OK.Next I will take the display board apart, since it is also full of dirt and sticky stuff and some dirt on the rubber buttons are so sticky that they only come out slowly.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 01:41:29 pm
content: OK, display PCB and assembly are all cleaned now.Also a picture of the dirty fan and rust / corrosion where the fan was mounted.This sticky stuff was everywhere inside the instrument in a thin layer.Now its time to re-assemble the meter again.

author: plesa
author_rank: Frequent Contributor
timestamp: December 13, 2015, 02:38:12 pm
content: Quote from: PA0PBZ on December 13, 2015, 11:59:07 amDone, it required bit of cleaningQuote from: HighVoltage on December 13, 2015, 01:41:29 pmStrange that my meters have the debug connector and yours not. Looking forward for test after cleaning. Maybe put it into oven and set it to 50°C for half hour.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 02:59:18 pm
content: Quote from: plesa on December 13, 2015, 02:38:12 pmThe alcohol evaporated really quick. So, I am thinking that the oven is not needed. Would have been a good idea but it is already assembled now.The fan in the 34410A in notoriously loud and I installed another fan with an additional 100 Ohm series resistor. The fan is still moving the air pretty well and I am just under the assumption that this should be enough airflow.Next thing is to turn it on and take some measurements.

author: Macbeth
author_rank: Super Contributor
timestamp: December 13, 2015, 03:07:37 pm
content: Oh you tease! You know we are all waiting with baited breath

author: plesa
author_rank: Frequent Contributor
timestamp: December 13, 2015, 03:14:58 pm
content: Quote from: HighVoltage on December 13, 2015, 02:59:18 pmHot air gun can do the job as well. Surface tension hold the liquid below IC for long period.Yes, the fans are horrible, maybe you can try to switch it off and check with thermal camera and later on stability against voltage standard.I make same experiment with L4411A where the fan is more noise and without cover it is OK, but with covers fan needs to be blowing air out of unit.34410A/34411A have more room for convection, so maybe it is not needed ( like 34401A which is passive only].

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 03:35:30 pm
content: It works !Well, at least it seems it works well so far.Here are some pictures of the first measurements.The 1 MOhm standard fluctuates a little too much, I thinkThe 100 Ohm measurement is almost rock solid at 10 NPLCThe 1 V, 10V and 100 V measurements are also rock solid at 10 NPLCI think the display strength has lost a little brightness on some segments.At least it appears to be not so bright on some spots.Ok, I will close the lid now and let it sit for a few hours and then take some detailedmeasurements from my known 10V DC Geller Labs SVRT standard.What else should I measure or look out for, to make sure it is all in order.BTW, the fan turns well but make almost no noticeable noise at all.It seems the repair of this first meter was a success so far.Thank you all for your suggestions.

author: plesa
author_rank: Frequent Contributor
timestamp: December 13, 2015, 03:47:39 pm
content: Congratulation to successful repair!! What about second unit?

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 03:55:14 pm
content: Quote from: plesa on December 13, 2015, 03:47:39 pmI have to wait for the switch and relay from Digikey for the second meter.But I will start cleaning it already and as you said, keep it in an oven at 50 degree for a few hours.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 05:28:58 pm
content: After about one hour, the 34410A has settled to10.00012 VMy Geller Labs SVRT is actually verified at10.000 028 82 Vby a calibration lab this summer.So, it seems the 34410A is off by about 100 uV in the 10V scale

author: plesa
author_rank: Frequent Contributor
timestamp: December 13, 2015, 06:26:24 pm
content: Quote from: 3roomlab on December 13, 2015, 06:06:29 pmIn this thread I posted noise measurement from 34411A,34410A and L4411A. On xdevs.com FTP are source data

author: HighVoltage
author_rank: Super Contributor
timestamp: December 13, 2015, 07:50:12 pm
content: I will measure the input noise in a few days.Then we have good comparison to plesa' meter.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 13, 2015, 09:13:56 pm
content: After cleaning with alcohol it may take a few hours in the oven or a few days of operation to drive out residual solvent from some parts or the PCB itself. So I would not take the absolute voltage reading to serious yet - this might still drift a little. At least it looks good.Ohne thing to check might be input bias/leakage current in the voltag ranges (especially 0.1 V and 1 V). E.g. measure the voltage when shortet with a 10 M or 100 M resistor. Alternatively measuring drift with a good quality 10 nF cap at the input should give a similar information.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 14, 2015, 09:04:07 am
content: Great suggestions, Kleinstein. I will do that in a few days, for now I will just keep it running on the Geller Labs SVRT.Here is a picture of the unit 14 hours later:The 34410A still shows10.00012 VIn comparison the Keithley 2450 is exactly at10.00000 V.

author: TiN
author_rank: Super Contributor
timestamp: December 14, 2015, 02:52:11 pm
content: And the voltnut was born...Good job, keep it up.I don't remember seeing much DMMs with triple-color VFDs! Green is rare in my book

author: jitter
author_rank: Frequent Contributor
timestamp: December 14, 2015, 05:56:45 pm
content: 10.00012 V is within tolerance, isn't it? I wouldn't be surprised if this is "as good as it gets".At work we have several 34401As and I hooked a few of them up to a calibrator set at a lowish value (I believe it was 5 mV) and the meters set to 6 digits readout. They all displayed a different value, but all within spec.Guess I'm not a voltnut, I often switch these meters to 4 digit mode to reduce the clutter on the display (those least significant digits are just noise to me) and speed up the update rate of the reading. This helps me adjust pots without overshooting the target and I find that the instruments I calibrate with these meters set at 4 digits are no less well calibrated than if I had done it with the meter set to 5 digits.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 14, 2015, 07:23:08 pm
content: I just hooked up the Keithley as a current source and it seems the 34410A is also full in specification in this current range.Now back on the SVRT.

author: plesa
author_rank: Frequent Contributor
timestamp: December 15, 2015, 09:25:51 pm
content: If you have such a decent SMU you can measure the input bias directly by SMUWhen I measured on 34410A it was 4.6 pA at 10M input impedance and about 0.65pA at Hi-Z mode.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 15, 2015, 09:56:56 pm
content: I would not trust the SMU very much at pA currents. Just the DMM itself and whatching a capacitor charge should be more reliable. Using just a resistor might measure a slightly different current, measureing mainly the active phase, if there is not much capacitance to average.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 23, 2015, 12:51:19 pm
content: OK, On to the repair of the second 34410AThe switch and relay arrived in the mail from Digikey and are installed.The unit turns ON and shows numbers on the displayBut no matter, if I use the front or rear input terminals, nothing gets shown ion the displayAs if the input is broken somewhere.No matter, if OHM, VDC VAC or anything else, if I apply an input signal to the terminals, it shows nothingThe displays stays at 0.0 and fluctuates around the noise level.Then I looked closer and found the damaged resistor next to K201So, will have a look what is broken there and for what reason.Stay tuned....

author: HighVoltage
author_rank: Super Contributor
timestamp: December 23, 2015, 03:17:40 pm
content: The big blue relay in the last picture is dead.This is K200 in the schematics and the input signal stops here.Its made by MEDER ElectronicsBT05-BV503243200-0121 (COTO number)0490-1914 (Keysight number)Rly-Reed 2A,5VDC CoilKeysight price is US$54.12Why is that one so expensive?I can not find anything comparable at Digikey or MouserFor now I will install a bridge to continue the repair.

author: dom0
author_rank: Super Contributor
timestamp: December 23, 2015, 04:22:35 pm
content: QuoteThe alternative Meder part is custom, too...@Blown-resistor.jpgQ305-Q307 ... HP continued to use the emitter follower stack/cascade to protect the ohms source? Why am I surprised to see it, itisa very nice design after all...

author: HighVoltage
author_rank: Super Contributor
timestamp: December 23, 2015, 04:25:28 pm
content: OK, it seems the input protection was blown...- Relay K200 was dead and did not turn ON- R210, 316 Ohm, burned up- L200, 10 uH, burned up- Relay K201, contacts burnedI replaced K201 with a new relay and just installed a 1 Ohm temporary resistor instead or R210/L200 to bridge it.And it worked !My 10V SVRT shows 10.00008VOK, now I need to find the relay and the two little SMD componentsHopefully all other measurements will work as well.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 23, 2015, 04:35:15 pm
content: Quote from: dom0 on December 23, 2015, 04:22:35 pmThanks for the info on the Meder RelayI probably order one from Keysight to get the original relay. But 50+$Yes, the emitter follower is really nice indeed.And guess what... 2 W resistance also works perfectly.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 23, 2015, 04:36:04 pm
content: Quote from: HighVoltage on December 23, 2015, 04:25:28 pmLooks like my 'parts donor' theory was not so bad after all...Good luck with the repair!

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: December 23, 2015, 05:21:11 pm
content: I ordered a replacement relay for one of my K2001 from herehttp://www.testco-inc.com/Good prices but I don't know if they have your model.

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 23, 2015, 07:00:35 pm
content: Hi, HighVoltage,might you please take a photo of R225, that is the 100:1 HighVoltagedivider, this white ceramic part, from both sides?I'd like to know, if that component is also used in the new 34465A/34470A... I assume that their schematics are very similar.May you please check also, if that component is heated (100mW), when you turn on the DC 1000V range without any input voltage.The heating connections are in the schematics, pin5 , versus pin6 GND.You should find up to 2.5...3.3V across this heating resistor.Would you mind to measure the value of this heating resistor, please?It should have less than 100 Ohm, probably 50 Ohm ,I guess.Very interesting part & principle, anyhow.Thanks a lotFrank

author: HighVoltage
author_rank: Super Contributor
timestamp: December 28, 2015, 01:27:58 pm
content: Quote from: ManateeMafia on December 23, 2015, 05:21:11 pmAfter looking around, I can not really find this exact relay anywhere.I will just order the original Keysight part number as a replacement.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 28, 2015, 01:47:27 pm
content: Quote from: Dr. Frank on December 23, 2015, 07:00:35 pmHello Frank,Here are some pictures of R225, the 10M Divider

author: HighVoltage
author_rank: Super Contributor
timestamp: December 28, 2015, 02:04:13 pm
content: Hello Frank,Ok I now measured the resistance and voltages applied to the heating element of the 10 M dividerResistance:54.87 OhmVoltage applied:2.33 VoltsThis is after warming up the instrument.The other repaired instrument was cold and the resistor is54.77 Ohm

author: Dr. Frank
author_rank: Super Contributor
timestamp: December 28, 2015, 04:28:52 pm
content: HighVoltage,thank you very much!I also opened my 34465A, and they still use exactly the same TaN divider from IRC, and the same technique. I found 55 Ohm and 2,311V.The trick is to compensate the self heating at 100V .. 1000V input voltages by applying external heat by this 55Ohm resistor.(2,33 V over 54,9 Ohm gives 99mW, like in my instrument)In any case, the total power dissipation is always about 100mW, so that the temperature of the ceramic array is constant in first order. (see attached table)Changing the ambient temperature might be a 2nd order effect only.So the ratio of this divider is always constant.Without this heating, the ratio changes by +10ppm.I always wondered, why the 3441x, 3446x and 34470 have no special HV calibration any more, only 500V.The 34401A, instead, has to be calibrated at 1000V and once at 500V to compensate numerically for this effect.The 3458A has no self heating compensation at all, and might drift by max. 12ppm @ 1000V. (my 3458A performs better, drifting only -1 .. -2ppm)P.S.: During the measurement, I discovered a new bug in FW 2.10 (not yet released officially), which concerns this heating mechanism.Frank

author: HighVoltage
author_rank: Super Contributor
timestamp: December 28, 2015, 04:48:14 pm
content: Hello Frank,Thanks for the explanation.Good to know that this is the same technology in the newer meters.I will take some IR pictures with my FLIR in the next few days and measure the surface temperature of the R225.By touch I would guess around 40 degree C

author: Vgkid
author_rank: Super Contributor
timestamp: December 29, 2015, 12:34:36 am
content: That is pretty interesting how they used a heater compensated voltage divider resistor.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 29, 2015, 12:42:39 pm
content: It looks like other people have searched for relay alternatives as well and have not been really successfulHelp me find a replacement relay...https://www.eevblog.com/forum/chat/help-me-find-a-replacement-relay/I will post close up pictures here as well.May be some day, someone will find a replacement and we don't have to spend this outrageous amount of money at Keysight.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 29, 2015, 01:04:07 pm
content: @Frank,I just measured the voltage at the heating element of R225 during power-upof the 34410A. For a few seconds, the voltage sits at3.16V, before it dropsto2.33 V.See pictureThere is also a slight difference in voltage at the heating element, dependingon the range selection, but it is really only visible in the uV range of the trendchart of the 34461A. (It shows the power of the trend chart in the 34461A)

author: branadic
author_rank: Super Contributor
timestamp: December 29, 2015, 05:52:02 pm
content: QuoteHave you tried contacting Meder? In the past they have been very helpful to me with their HF/RF reed relays. Maybe they help you too, as their slogan is "We matter.". You can refer to this when writing them

author: Macbeth
author_rank: Super Contributor
timestamp: December 29, 2015, 08:30:33 pm
content: Quote from: HighVoltage on December 29, 2015, 12:42:39 pmNo pictures of its internals? I always tear these things apart when they are done for. Sometimes you can get lucky and fix a mechanical problem and get some extra life out of them.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 29, 2015, 11:16:45 pm
content: Quote from: Macbeth on December 29, 2015, 08:30:33 pmWell, I thought about taking it apart, but .... it is potted with epoxy resin.I will try to remove the epoxy slowly with some acetone.May be I can get to the internals.But I doubt that it is repairable since it is not even actuating when 5 V DC is applied.However, we might get a good look inside this ultra expensive relay@branadicThanks, I did send an email to Meder. Will probably get an answer after the new year.

author: plesa
author_rank: Frequent Contributor
timestamp: December 29, 2015, 11:22:48 pm
content: You can make Xray picture at dentistThanks for details about 10M resistor.

author: branadic
author_rank: Super Contributor
timestamp: December 30, 2015, 08:35:08 am
content: QuoteYou can find the BT series on their website:https://standexelectronics.com/de/produkte2/bt-bts-reed-relais/It's a 5V Reed Relay. Is the relay located in front of the resistive voltage divider? If so, my best guess is, that they got a special 1000V version, that is not available in their catalog. Seems like the form factor doesn't match the standard reed relays.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 30, 2015, 10:44:05 am
content: Quote from: plesa on December 29, 2015, 11:22:48 pmWell, X-Ray would not have helped.The housing of this relay is made of ferrous / magnetic metal, 0.7 mm wall thicknessSo, I took the brutal method of a saw, to take it apart.Here are some picturesThe reed part is suited in the center core of the winding and is made out of glassUnfortunately it did not survive my mechanical intrusion.It seems the glass reed contact part is just inserted to the hollow core part of the coil and then everything is pottedIt also seems the potting material is not of epoxy, as first thought, but of PolyUrethan material.It has been a long time, since I have seen a modern relay in a metal housing.I would assume it is to protect the reed relay from actuating through an outside magnetic field.But then, where would that magnetic field come from in such an application.It is probably the 1000 Volts rating that makes this relay so expensive.Here are some pictures of the brutal teardown.The last picture shows the actual contacts that used to be in a glass housing / tube

author: HighVoltage
author_rank: Super Contributor
timestamp: December 30, 2015, 10:56:03 am
content: Quote from: branadic on December 30, 2015, 08:35:08 amThanks, may be they offer a free sample, if I can not buy it.They will probably not answer before the new year.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 30, 2015, 10:59:27 am
content: OK, I took some IR pictures of the R225Instrument cold = 22°C (Room Temperature)Instrument warm = 30°CSo, it seems the R225 is heated by about +8 degrees after 1 hourHere are some IP pictures from my FLIR upgraded E4.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 30, 2015, 11:15:00 am
content: The main reason for the high price is likely the small number of relays of this type made.The metal can is more to protect the surrounding circuit from the stray field. It also helps to keep temperature gradients low.The special features the relay should have the hight rated voltage, low leakage to coil and low thermal EMF.The low thermal EMF is likely the reason for using two contacts in series.Just for the basic function one could try something like aMEDER LI05-1A85though different form factor and just one contact, thus likely not low thermal EMF.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 30, 2015, 11:32:44 am
content: @Kleinstein,Good points on the metal can and low EMFWhen I get the new relay, I will take some measurements compared to a "normal" relay. This might be interesting.@3roomlabI did not expect those contacts to be easier available than the relay.ThanksHere is a picture of the reed tube contact form the website you provided.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 30, 2015, 11:34:41 am
content: Quote from: 3roomlab on December 30, 2015, 11:26:58 amThose are pretty cool relays for up to 15 kV

author: dom0
author_rank: Super Contributor
timestamp: December 30, 2015, 12:48:42 pm
content: That's "COTO goodness red". The metal part looks like anexternalshield?!

author: Kleinstein
author_rank: Super Contributor
timestamp: December 30, 2015, 06:04:07 pm
content: The external metal can also function as a magentic return path. So the relay can get more sensitive and use less power. Low power can also be important to get thermal errors down.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 06, 2016, 12:55:08 pm
content: I am still after the relais from Meder and may be they can supply it.In the meantime I got the official Meder datatsheet for this relais, see attachmentMEDER Relay BT05-BV50324

author: Kleinstein
author_rank: Super Contributor
timestamp: January 06, 2016, 01:27:14 pm
content: The datasheet shows the relais is a custom design for Agilent. This might also explain the rather high price.It also shows it is rather low power and made with thermal EMF in mind. There is a thermovolateg specification, though not that low - but this could be a worst case conservative value, in the DMM enviroment this should be much lower. Also having copper alloy pins might be important to have the low thermal EMF - other reed relays might have kovar leads.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 06, 2016, 01:55:43 pm
content: Quote from: Kleinstein on January 06, 2016, 01:27:14 pmYes, I talked to Meder Germany in detail about this and they confirmed it was only made for Agilent in their chech republic factory.http://www.relmag.cz/produktyThey are "looking" now, if they still can find one of these ralais in the factory or if they can find their BOM and build one.I am kind of amazed that I got such good quality reaction from Meder.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 09, 2016, 02:46:41 pm
content: After a few days, Meder came back and let me know that they can not supply the relay because of exclusivity to Keysight and they also do not have anything similar that would fit either the footprint of the other specifications. Hmm bummer. So I will get the original Keysight replacement relay.Otherwise the unit is repaired.I found a 10 uH inductor that was a little larger than the original but got it fitted alright with some wires and a new resistor is also installed. A quick test shows that the meter is within calibration specs fro DC volts and OHM.Only thing missing is the relay now and then a full calibration check.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 12, 2016, 06:12:25 pm
content: OK, a quick follow up .... Repair is successfully completed.Parts from Keysight arrived.There was no way around this expensive Keysight relay, as Meder would not sell me anything.- Installed the relay- Installed new front connector block, because the contacts did not look so nice- Installed new low noise fan.- Reassembled the meter.Hooked up to my Geller Labs SVRT, showing: 10.00001V after warmup.Looks like another great addition to the lab.Thanks for all your input.

author: TheSteve
author_rank: Unknown
timestamp: February 12, 2016, 08:59:28 pm
content: Looks great - just how many bench DMM's do you have in the lab now?

author: chihaxinh
author_rank: Regular Contributor
timestamp: February 19, 2016, 04:01:38 am
content: HI High VoltageWhat cause can kill relay ? Overvoltage or short to burn coil ? So many 34401A using and hard to finding relay to replace

author: HighVoltage
author_rank: Super Contributor
timestamp: February 19, 2016, 10:17:31 am
content: Quote from: chihaxinh on February 19, 2016, 04:01:38 amI think this one was killed by over voltage, probably far exceeding the 1000V DC limit of the meter, because of the damaged components in the input signal path.Yes, I was also very much surprised that such a relay could not be obtained from "normal" vendors and that I had to buy it from Keysight. No other option. May be one day someone will find a better sourse.Quote from: TheSteve on February 12, 2016, 08:59:28 pmWell, we had this thread here called "Why does everyone have 20 Oscilloscopes" or soI probably have 20 Bench DDM's, if I add all my lab benches together.Most of them Agilent / Keysight but also a few old BBC Metrawatt meters.May be I should make a picture with all of them?

author: TheSteve
author_rank: Unknown
timestamp: February 19, 2016, 06:58:10 pm
content: A picture would be great. I'd need more bench to have that many meters, it does sound fun though. Twenty DMM's is better then twenty scopes...

author: HighVoltage
author_rank: Super Contributor
timestamp: February 20, 2016, 10:53:50 am
content: OK, here we go,I just gave two HP branded 34401A meters away to a friend after repair otherwise they would have been in the picture as well.These are all my bench top meters from different benches. First time they are lined up like this on the same table.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: February 20, 2016, 10:59:40 am
content: HighVoltage, if you ever feel again in a give away mod on another 34410A, and want to send it my away I don't mind give him a new home.

author: TiN
author_rank: Super Contributor
timestamp: February 20, 2016, 03:19:58 pm
content: No 3458? BoooNice stash. Now hook them all to stable 10V and make some neat charts...

author: TheSteve
author_rank: Unknown
timestamp: February 20, 2016, 06:39:41 pm
content: Quote from: HighVoltage on February 20, 2016, 10:53:50 amNow everyone will want to be your friend!Great shots, so much great HP/A/K gear with just a few Keithley goodies tucked in.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 21, 2016, 01:20:39 pm
content: Quote from: TiN on February 20, 2016, 03:19:58 pmThe 3458A is still on my wishlist. It is not easy to find a good one that is also right in the price range.May be one day I will have one.Good idea to hook them all up and make a comparison chart.Indeed, that will be interesting, let me see if I get to that.I need to build a few cables first to hook them all up at the same time to my 10V SVRT.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 21, 2016, 01:32:49 pm
content: Quote from: TheSteve on February 20, 2016, 06:39:41 pmThe Keithley Source meters are just amazing, especially the 2450 with the high precision in the lower values.This 1 nA DC current measurement with the 34470A had the 2450 as a 1nA source. (See pictures)But somehow I find the 34401A and the 34410A easier to repair than the Keithley meters.But then .... may be I am just addicted to Agilent gear and not so much to Keithley instruments.

author: Helix70
author_rank: Unknown
timestamp: March 06, 2016, 02:08:34 am
content: When did the Agilent 34401A front panel change from rectangular buttons to rounded ones? Mine are rectangular..

author: Macbeth
author_rank: Super Contributor
timestamp: March 06, 2016, 04:28:28 am
content: Quote from: Helix70 on March 06, 2016, 02:08:34 amIt's a 34410A not a 34401A.Yeah, I didn't know about them before this thread either. On my radar nowETA: Oh, it looks like the '01s with the rounded buttons are a thing. The Keysight version?

author: HighVoltage
author_rank: Super Contributor
timestamp: March 06, 2016, 10:43:09 am
content: Quote from: Helix70 on March 06, 2016, 02:08:34 amI think the round button on the 34401Awas introduced around 2009 or 2010, by Agilent, long before it became KeysightIt was kind of a facelift with no other technical changes.The Keysight branded 34401A kept everything the same besides the logo.The 34410Aalways had round buttons as far as I know.

author: Helix70
author_rank: Unknown
timestamp: March 08, 2016, 01:00:54 pm
content: I have a 34401a that is missing a serial number sticker. The calibration message says 2006-06 with 35 calibration counts. The anti tamper stickers are in tact on the rear screws. Any way to date the meter and is there another way to get the serial? *idn? Says 0.Was the original cal 2 years after manufacture?

author: HighVoltage
author_rank: Super Contributor
timestamp: March 08, 2016, 04:11:19 pm
content: Quote from: Helix70 on March 08, 2016, 01:00:54 pmYou can find out the serial number by requesting it through GPIB or Serial interface on the 34401A.The serial number is part of the returned IDN string for the instrument.The IDN string is usually returning the following string:<Manufacturer>,<Model Number>,<Serial Number>,<Firmware Revision>When sending "*IDN?" to the Agilent 34401A, you should see something like:"AGILENT,34401A,0,11-5-2"The calibration cycle depends on the user and it can be 1 year or two years.

author: plesa
author_rank: Frequent Contributor
timestamp: March 08, 2016, 05:40:33 pm
content: Quote from: HighVoltage on March 08, 2016, 04:11:19 pmWith this example the meter does not contain serial number, there are lot of instruments made by HP and Agilent which will respond to *IDN? query like HighVoltage mentioned (HEWLETT-PACKARD,34401A,0,10-5-2 in my case).These meter does not contain SN.Also calibration count does not count the number of calibrations but more it is counter of value changes, so during one calibration you can change cal count more than +1 only.

author: Helix70
author_rank: Unknown
timestamp: March 09, 2016, 10:25:31 am
content: Sorry, i wasn't clear.. The field for serial number on mine returns a 0. I get the full message for *IDN?

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2016, 11:54:48 am
content: I bought another one of these meters, well, this one is the34411A, the big brother to the 34410A with higher speed and a much higher price sticker. My price was Euro 100. The official price in Germany is right now crazy Euro 2600 incl. VAT.This one was offered to me broken - "Not turning ON" and I expected another nice repair job for a Sunday.But I opened it up and found the power cable from the transformer unplugged from the PCB ... hmmm what an odd thing to discover.Interestingly the fuse was also blown.Solution:Plug in the cable, replace the fuse and turn on.It seems to work well.This unit was sold by Agilent in 10/2012Date-codes on the chips are 2212This instrument has the yellow Kapton tape on top of the electrolytic capacitors, same as some of the last 34401A instruments I got.But the previous 34410A that I repaired did not have the tape.May be the changed production procedures to protect the capacitors from heat?OK, I will start some sampling from my Geller SVRT to see if the unit has a drift.May be I should get it fully calibrated.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2016, 11:59:49 am
content: two more pictures

author: lowimpedance
author_rank: Super Contributor
timestamp: September 11, 2016, 12:02:35 pm
content: Quote from: HighVoltage on September 11, 2016, 11:54:48 am......... geez some guys have all the luck!.Nice meter btw.

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: September 11, 2016, 12:22:51 pm
content: HighVoltage, you've to tell me how you find this things, I'm still looking for a 34401 to fix, or one of that for a decent price, but seems I can't find any at that price range.Nice score. :-)

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2016, 01:00:33 pm
content: Quote from: Nuno_pt on September 11, 2016, 12:22:51 pmThanks...It works best when the seller:1. Puts the instrument it in a wrong category2. Does not know how to spell "Aiglent"3. Does not turn the unit on to proof its working4. Mixes up the model number eg 3401 instead of 34401ABut you have to take a risk as well.Sometimes I buy "the cat in the sack" when there is only a stock picture shown.Many times I get lucky but sometimes I also lost in the past.Most of those time Paypal Protection helpsIf you keep looking, you will finally get one.Look on ebay France, they really don't know how to spell English words correctly - many times.And usually I find interesting instruments there.But I better stop talking, otherwise I will no longer find these scores.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2016, 01:06:56 pm
content: 1 hour laterInterestingly, the 34411A shows the lowest standard deviation of 1.5 uV

author: plesa
author_rank: Frequent Contributor
timestamp: September 11, 2016, 03:26:35 pm
content: Congratulation to additional 3441xA meterYou are like TiN with Keithley DMM

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 11, 2016, 07:41:14 pm
content: Hello HighVoltage,and congrats to your crisp 34411A.As the 465A/470A with Digitizing option are promoted to be successors to the 34411A,but do not perform well regarding data transfer in BenchView, would you mind checking, if the 34411A operates better?That means, is it possible to transfer data in real time to benchview, with highest sampling rate 50kSa/s, w/o delay due to buffering?THXFrank

author: bitseeker
author_rank: Super Contributor
timestamp: September 11, 2016, 09:44:54 pm
content: Quote from: lowimpedance on September 11, 2016, 12:02:35 pmYou can say that again. Nice score, HV! Amazing.

author: plesa
author_rank: Frequent Contributor
timestamp: September 12, 2016, 06:23:21 pm
content: Quote from: Dr. Frank on September 11, 2016, 07:41:14 pmHi Frank,is it related to BenchVue?I have one application where I needs to digitize 50k samples/s with 34411A. And it seems to be working well in LabView( following setting was essential:FORM:DATA REAL,64:FORM:BORD NORMreading is by R? command)Do you have dump of SCPI sequence which is used by BenVue and 34470A?

author: HighVoltage
author_rank: Super Contributor
timestamp: September 12, 2016, 07:20:34 pm
content: Quote from: Dr. Frank on September 11, 2016, 07:41:14 pmHello FrankOK, I just hooked three instruments in parallel to my 10V Geller SVRTAll three instruments are hooked up to BenchVue via Network Cable on a 1 gbit networkThis is what I get for collecting 1 Mega Samples at fastest acquisition time:34410A10.024 KSa/secTime for collecting data: 99 Sec34411A50.118 KSa/secTime for collecting data: 19 Sec34470A25 KSa/secTime for collecting data: 40 SecI can send you the exported Excel files, if you like.It is interesting how the screen of the three instruments are changing to just show the word: "DIGITIZING"Is this what you wanted to know?Or do I need to do some more test's

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 26, 2016, 01:03:03 pm
content: Quote from: HighVoltage on September 12, 2016, 07:20:34 pmHello HighVoltage,sorry that I discovered your post and answer so late!No, that's not yet the crucial test, because with these settings, both instruments (411A and 470A) will handle all the digitizing fully inside internal memory. If you increase the number of samples to more than 1MSa for the 411A, and more than 2MSa for your 470A @ 50Khz also (has to be manually set to digitizing at the instruments panel!), then you might notice a delay and even data loss, as at least the 470A is not able to transfer data fast enough over the bus, at first due to the ASCII format.The 411A may have a dedicated state machine, or faster SW code, to handle that fast transfer to PC, as specified in its manual (*)(lacking for the 470A!), and might also transfer in 4 byte / 8 byte format, which would be 4 or 2 times faster, than with the ASCII transfer.Would be nice, if you could test again with 50kSa/ sec and 4MSa for both.THX!FrankPS: I assume, that both instruments don't have the possibility to transfer data directly to PC, omitting the buffer.This method is available on the 3458A (@ >100kSa/sec), and allows real-time digitizing.(*) "Direct I/O Measurements", and "Maximum reading rate out of memory"

author: HighVoltage
author_rank: Super Contributor
timestamp: September 26, 2016, 01:48:16 pm
content: OK, I will do some more acquisition tests this week.

author: plesa
author_rank: Frequent Contributor
timestamp: September 26, 2016, 06:28:12 pm
content: I'm using 10k-50k sample count and on NPLC 0.001 and with binary data format (:DATA REAL,64;) and there is no gap in data and digitizing looks like realtime @ 50k/sec.If I remember testing few years ago there is no big difference between maximal rates on USB or GPIB.

author: USMCBYRD
author_rank: Newbie
timestamp: December 01, 2016, 08:54:41 pm
content: Gents (ladies),I am attempting, and I use that term very loosely, to repair a 34410a that has a faulty USB connection. Upon disassembling the instrument it was immediately apparent someone had shorted something with higher voltage to the connection. The components located at T1001 and FB1005 were blown completely off the CB. I have been searching the internet for days trying to find out what these components are. I believe they are a Transformer and Ferrite Bead. I would like to order replacements to see if I can get the USB connection back up and running. Can anyone help me determine the parts I need to order? I greatly appreciate any help you can give. Thank you.

author: HighVoltage
author_rank: Super Contributor
timestamp: December 01, 2016, 09:15:45 pm
content: Can you show pictures of the broken parts?

author: plesa
author_rank: Frequent Contributor
timestamp: December 01, 2016, 09:17:43 pm
content: Here is part of schematic of 34410A related to USB. Is meter able to pass self test?Exact values should be in manual for Cypress chip.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 05, 2020, 03:33:19 pm
content: A forum member asked me to show a high resolution picture of U305 in the Keysight 34410A.Here it is.

author: faraday
author_rank: Regular Contributor
timestamp: January 15, 2021, 08:05:18 am
content: Quote from: HighVoltage on February 12, 2016, 06:12:25 pmDo you have part nr for installed FAN? I want to mod my noisy meter and looking for low noise replacement.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 15, 2021, 09:09:33 am
content: This was a long time ago, but I think I have used aSunon MF40100V2-1000U-A99In addition I have placed a 100 Ohm resistor in series to slow it down.https://www.mouser.de/ProductDetail/Sunon/MF40100V2-1000U-A99?qs=EU6FO9ffTwcmA4g%2FuEYqgQ==

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: January 15, 2021, 09:42:39 am
content: Quote from: HighVoltage on September 11, 2016, 01:00:33 pmyeah, thanks for being the party pooper!

author: HighVoltage
author_rank: Super Contributor
timestamp: January 15, 2021, 01:15:58 pm
content: No worries, I have plenty of benchtop DMMs by now. Maybe too many

author: bitseeker
author_rank: Super Contributor
timestamp: January 16, 2021, 08:22:41 pm
content: Maybe...

author: coromonadalix
author_rank: Super Contributor
timestamp: January 17, 2021, 01:42:56 am
content: surely loll

author: HighVoltage
author_rank: Super Contributor
timestamp: September 11, 2021, 11:08:58 am
content: Newest addition, a broken 34411A.Problem was that unit turned ON but buttons did not react to any push.Somehow this unit was in a strange environment and all the carbon pads had corrosion on the PCB.I never had this problem before. I cleaned it all with alcohol and it works like new.This instrument is newer than the previously shown and is from 2013.Here are some pictures for your enjoyment.Also interesting, the metal shielding around the front VFD area.The 34411A is a very well made meter.

author: bitseeker
author_rank: Super Contributor
timestamp: September 18, 2021, 08:57:47 pm
content: Good thing it didn't eat away the contacts. Nice find and recovery!

author: HighVoltage
author_rank: Super Contributor
timestamp: April 30, 2022, 12:48:15 pm
content: Well, another broken 34410A found its way to me.This one passes the self test and works well in all DC ranges but all AC measurements are wrong.Looking forward to the repair, but need a time slot first.

author: bitseeker
author_rank: Super Contributor
timestamp: June 06, 2022, 12:56:34 am
content: Looking forward to it, HV.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 06, 2022, 09:15:35 am
content: The repair was much easier than I had expected.The 1 MOHM input resistor is divided into tiny 5x 200 kOHM resistors for high voltage reasons, I assume.Two resistors (R465 and R466), and one parallel capacitor (C465) were dead.The large input capacitor C400 was perfectly OK.I exchanged all the small resistors and capacitors and now the unit performs well.

author: 412jim
author_rank: Newbie
timestamp: February 20, 2023, 02:58:55 pm
content: Anybody know where I can find a front/rear push rod (PN 34410-43712) for a 34410A? I just need the plastic front panel push button part, the switch works fine. I searched pretty deep on google but couldn't find anything.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 20, 2023, 03:45:59 pm
content: tried to get them at keysight usa ....nada maybe elsewhere or 3d print one ??even the short one .... nadanot sure if the ones for the 34401a are the same lenght

author: HighVoltage
author_rank: Super Contributor
timestamp: February 21, 2023, 07:22:23 am
content: I am traveling right now, but when I am back in my lab, I can look.I think I ordered a few, many years ago, when they were still available.The 34401A has a completely different rod from the 34410A

author: 412jim
author_rank: Newbie
timestamp: February 21, 2023, 03:10:46 pm
content: A 3D print is the backup plan, but an OEM part is preferred.Thanks for checking HV. Let me know...

author: Bruce Savage
author_rank: Newbie
timestamp: August 30, 2023, 12:18:34 am
content: Hello I'm new here. I just bought a 34410a on ebay. The fan was mounted with the label facing the rear of the unit and was turning clockwise when viewed from the rear. So it was sucking air out of the unit. What confuses me is that the decal on the back with the number '40' inside seems to indicate that it should be turning counter clockwise. So is the fan supposed to be sucking air out or pushing air in?

author: HighVoltage
author_rank: Super Contributor
timestamp: August 30, 2023, 03:37:01 pm
content: Welcome to the forumThe picture is just a symbol that something is rotating.It is correct, that the fan turning clockwise and is blowing out the air from the instrument.

author: Bruce Savage
author_rank: Newbie
timestamp: August 31, 2023, 12:43:49 am
content: Quote from: HighVoltage on August 30, 2023, 03:37:01 pmThank you for helping me with that