Keithley 2002 repair (Help please) - Page 1
Forum section: electronics / repair

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 03:21:30 pm
content: Hello good people of the EEVblog ForumTo me: I live in Switzerland and am a soon to be student that studies electronics engineering.To the subject: A while back I bought a defective Keithley 2002 from an auction site and put it aside. Now I have some time in hand and would like get it running again.I have read through the excellent posthttps://xdevs.com/fix/kei2002_u2/and some other posts on the forum that successfully repaired a Keithley 2002 or similar.To the device: It came with the cap C117 and rectifier CR113 missing. To be seen at 'pic2'. The LCD lights up fine but on whatever you choose, Voltage, Ampere etc. it shows 'overflow', as to be seen on 'pic1'. I have measured the Voltages and they seem as following:5V -> measured about 4.1V+15V -> measured about 2.2V-15V -> measured about 1.1VThe device fails so many tests, that I did not bother to look into those.After that I carefully removed all the electrolytic caps on the analog board. The reason for that is that, the inside really smelled fishy and I have heard many times that it is good practice. 'pic3'To no ones surprise it was a great idea because, some of the caps already started leaking. 'pic4 and 5'The caps I removed look fine, besides one 'pic6 and 7' The one on 'pic7' is not near its rated capacitance, it measures some nanofarads. I hope that that is why the Keithley did not workI cleaned everything nicely with isopropanol and looked at the traces. None of them see to be damaged severly, as far as I can see no damages have been done. 'pic8'.I am currently making a basket with all the caps I need (electrolyte and tantal). I will install everything this friday probably and here is where I need your help.I am suspecting that the device wont work, because that would be too easy woudlnt it be?If anyone has any other suggestions or places that I should check while waiting for the parts, Id be really greatful to hear them.Thanks everyone in advance and greetingsSelectLOLSorry for the image quality, had to resize alot to be able to post

author: Kleinstein
author_rank: Super Contributor
timestamp: July 27, 2022, 04:01:06 pm
content: Unless one of the old electrolytics has a short, there is likely something else wrong at the +-15 V supply to let the voltage drop that much.A point to check (in circuit should be OK) would be the rectifiers to see if there is a shorted diode. It very much looks like something is pulling down the -15 V and likely also the +15 V. The low voltage for the 5 V may be from the transformer voltage going down from overload, but also from current flowing from the +5 V towards the +15 V rail. Some of the CMOS switches may have both a 5 and 15 v supply and may provide a parasitic path.The damage to the PCB does not look too bad, but it would still need quite some cleaning to be on the safe side. The nasty part is contamination below the SMD chips and resistors. One may have to remove some, just for better cleaning.For a first test one should probably leave out the ADC board, and check the supplies.

author: Sarvesaa
author_rank: Contributor
timestamp: July 27, 2022, 05:16:38 pm
content: That rectifer looks abnormal check that up.We both are the same catergory. I completed high school and in one month time, I will be studying EE as you do.The repair will go alright.Thank YouWith RegardsSarvesaa

author: alm
author_rank: Super Contributor
timestamp: July 27, 2022, 05:29:52 pm
content: I'd try to measure resistance across the plus and minus 15V rails. So +15V to the ground for that rail, and then -15V to ground. I believe the power supply is linear, so if the rails are so low, then either the regulator is open or there's a low resistance across the rail. After removing the caps and cleaning the pcb, but before putting in the new caps, would be the perfect time because large caps make resistance measurements more difficult.

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 06:37:18 pm
content: Quote from: Kleinstein on July 27, 2022, 04:01:06 pmThe old electrolytics dont have any shorts. As far as I can only measure the capacitance with my Multimeter, only the red one is far off. The othner ones seem kinda fine. (I will of course change them).Quote from: Kleinstein on July 27, 2022, 04:01:06 pmWhen I bought the device it had the CR113 and C117 were missing. The Repair Manual for the 2002 says, that CR113 is the rectifier for the +15V and -15V rails. And C117 has something to do with the Bootstrap supply (about 38V). I have put a screenshot in the Attachments. It should be page 21/148 from the manual (2002_902_01B)Quote from: Kleinstein on July 27, 2022, 04:01:06 pmYeah I havent thought about the underside of the SMD parts you are right, there might be some electrolyte left there. I will give it a good cleanup again and hope for the best, Im to afraid to desolder anything else besides the caps.Is there anything else that comes up to your mind that might be worth measuring? I have found some testpoints on the board but no place where it says what voltages I should expect there

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 06:41:20 pm
content: Quote from: Sarvesaa on July 27, 2022, 05:16:38 pmYeah when I bought it was just missing (screenshot of the functionality on my answer before), very weird, somebody must have had tried somethingQuote from: Sarvesaa on July 27, 2022, 05:16:38 pmAhahahah thats amazing, I wish you all the luck and great success in your studiesThank you for checking in

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 06:45:46 pm
content: Quote from: alm on July 27, 2022, 05:29:52 pmThank you for your suggestion, I have measured between +15V and -15V, currently the larg caps are disconnected as on the pictures from the original post and the analog board is connected to nowhere. The measured resistance is 2.4kΩ, I think thats not to low or to high, what do you think? Anything else that I should measure before continuing?

author: Zucca
author_rank: Unknown
timestamp: July 27, 2022, 06:49:18 pm
content: When you try to fix a 8.5 DMM it could be a never ending story.I wish you luck.Do not be discouraged by the above lines, the opposite.What you are doing it is one of the best way to learn, and learn a lot.Go slow and do not cut corners, always document/post here your progress.Even if you do not bring it back to life, you are not wasting time.PS: Very interesting stuff here too:https://www.eevblog.com/forum/repair/keithley-2002-repair-help/To the repair, a voltage supply issue is promising. Use IPA alcohol or finger to spot high temperature components that maybe are in short....If nothing is warm, you need to check the components that should generate the +-15V

author: alm
author_rank: Super Contributor
timestamp: July 27, 2022, 07:00:30 pm
content: Quote from: SelectLOL on July 27, 2022, 06:45:46 pm2.4kOhm sounds sensible to me. How about measuring just +15V to its ground and just -15V?

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 07:34:09 pm
content: Quote from: Zucca on July 27, 2022, 06:49:18 pmThank you very much. My main goal, even above getting the Keithley back to a running state, is to learn something new. So my motivation is always highQuote from: Zucca on July 27, 2022, 06:49:18 pmI really love the way the forum works and how you can keep people updated and get help from them. I will definitely write down every little step of mine, so that someone, somewhere, with the same problem, might resolve his problems.Quote from: Zucca on July 27, 2022, 06:49:18 pmInteresting technique with the IPA alcohol to find out high temperature areas. I know someone, which I hopefully might be able lend me a IR-Temp camera to measure high temp. areas in the near future.In my last comment I posted a screenshot of the repair manual, which shows me that the rectifier for +-15V is missing. I got it that way when I bought it

author: SelectLOL
author_rank: Contributor
timestamp: July 27, 2022, 07:50:11 pm
content: Quote from: alm on July 27, 2022, 07:00:30 pmSo I took those measurements of the bottom side of the Analog Converter Board, because they were nicely labeled.+15V to VGND -> 183k+15V to GND -> 2.9k+15V to DGND -> 38k-15V to VGND -> 185k-15V to GND -> 1.7k-15V to DGND -> 35kAll the measurements were either rising or falling, seems to be connected to some sort of capacitance. But all in all that seems fine, right?In the attachments there is a picture from where I measured.VGND 3. from top, GND 5. from top and DGND 2. from bottom

author: alm
author_rank: Super Contributor
timestamp: July 27, 2022, 10:04:55 pm
content: Quote from: SelectLOL on July 27, 2022, 07:50:11 pmYes, none of the values are low enough to draw the rails down. When you have the caps replaced and can power it up again, my next step would be to look for hot components like Zucca suggests. An oscillating op-amp, for example, can also draw a lot more current than normal.I would also measure the voltage around the +/- 15V linear regulators, like the input voltage into the regulators and the AC voltage that's going into the bridge rectifier for the +/- 15V rails. The problem with the 15V rails could also be at the supply side, like an open transformer winding, though this appears less likely.

author: SelectLOL
author_rank: Contributor
timestamp: July 28, 2022, 06:13:22 am
content: Quote from: alm on July 27, 2022, 10:04:55 pmThank you, I will be posting my basket from Farnell later on. The parts should arrive tomorrow hopefully, then I can measure out said points and post the results.

author: SelectLOL
author_rank: Contributor
timestamp: July 28, 2022, 07:57:02 am
content: Alright, so this is my final Shoping Basket/Cart. I have selected all (besides one rated for 2000hrs) to be rated for 10000hrs @ 105C. The size of the caps should be the same too. I also added some tantalum caps to the basket, which I might change later on. If I get the meter fully running, I will change all the other caps too, I am just on a tight budget currently.For the missing rectifier CR113, I found out that the part ishttps://ch.farnell.com/vishay/df02m-e3-45/br-ckengleichrichter-diode/dp/1651041?ICID=I-RP-STM7REC-3but it is currently not available. I will be ordering the SMD varianthttps://ch.farnell.com/vishay/df02s-e3-77/br-cken-gr-diode-1ph-1a-200v-dfs/dp/2335133instead. It should be fine, right?I will be ordering in a few hours if something critical is missing please let me know, thank you.The Shopping Basket/Cart can be found in the attachments as ZIP, which contains a HTML file from Farnell.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 28, 2022, 09:13:34 am
content: For the rectifier there should be THT versions available. It does not matter if the current rating is a little higher or the voltage rating is different, as longs as it is sufficient (e.g. >=60 V). The round form may also fit.There is not need to change all the capacitors. Just the electrolytics are some-what critical.

author: SelectLOL
author_rank: Contributor
timestamp: July 28, 2022, 09:23:47 am
content: Quote from: Kleinstein on July 28, 2022, 09:13:34 amAlright then, I will choose this one instead >https://ch.farnell.com/multicomp/df04/br-cken-gr-diode-1phase-400v-1a/dp/2748159?MER=sy-me-pd-mi-acceAs far as I have understood only the Voltage changes for this one from 200V to 400V so it should be fine.Quote from: Kleinstein on July 28, 2022, 09:13:34 amI see, I see, so I will leave the ones I already selected and only focus on the electrolytic ones for future changes, thank you.I will order now then, so that everything definitely arrives tomorrow

author: Per Hansson
author_rank: Unknown
timestamp: July 28, 2022, 10:20:48 am
content: CR112 looks like it overheated? I would replace it also!

author: SelectLOL
author_rank: Contributor
timestamp: July 28, 2022, 11:08:29 am
content: Quote from: Per Hansson on July 28, 2022, 10:20:48 amThank you very much for pointing that out, I have found following replacement and have added it to my basket :https://ch.farnell.com/multicomp/w04mg/br-cken-gr-diode-400v-1-5a-wob/dp/1861437?ost=w04m

author: manicdoc
author_rank: Unknown
timestamp: July 28, 2022, 10:26:26 pm
content: Quote from: alm on July 27, 2022, 05:29:52 pmAgreed. Try as much as possible to get power rail resistive measurements per board in isolation, and write it down, compare and do the power maths...

author: SelectLOL
author_rank: Contributor
timestamp: July 29, 2022, 09:05:35 am
content: Quote from: manicdoc on July 28, 2022, 10:26:26 pmThank you, I will try to measure some more points and document and post them.

author: SelectLOL
author_rank: Contributor
timestamp: July 29, 2022, 09:13:11 am
content: Quote from: SelectLOL on July 28, 2022, 11:08:29 amAmazing, I have soldered CR112 out to see if its intact, looks like it bit the dust. My measurements can be seen in the attachment. Please tell me if I have measured something wrongly. Thank you, luckily I already purchased the replacement

author: free_electron
author_rank: Super Contributor
timestamp: July 29, 2022, 12:17:46 pm
content: many of these machines die due to the capacitors leaking. some are unrepairable. the leaky electrolyte has caused electromigration on inner layers and created hard shorts. your ohmmeter may tell "open" but the moment you apply a voltage that stuff goes short.i;ve repaired a few and had 2 that were not repairable.check out the glass diodes close to the capacitors. they sometimes get fried too.

author: IanJ
author_rank: Unknown
timestamp: July 29, 2022, 01:49:22 pm
content: Nice clean looking unit, including it's PCBs. Looks like you caught it in time with those leaky caps.......it's a whole different ball game if the PSU side of things fails.....trust me!Ian.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 30, 2022, 09:18:24 am
content: It seems to me that Keithley instruments are much more prone to have leaky electrolytics, compared to other instrument manufacturers. Especially the 2001 and 2002 models.Why is that?Compare this to the Agilent 34401A, I never had one bad electrolytic capacitor, not even on the older models.

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 10:01:16 am
content: Quote from: free_electron on July 29, 2022, 12:17:46 pmOu thats very interesting, so the only way you can actually tell is by applying voltage and checking for abnormal temp. and current drawing? Luckily mine isn't that far gone, that that can happen, right?Quote from: free_electron on July 29, 2022, 12:17:46 pmOh what an amazing feat! Glad you are helping me outI have looked into those diodes and they seem to be described as "Avalanche" Diodes and I really had to google first what they even are. I will test them now before soldering up everything together, thank you.

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 10:03:54 am
content: Quote from: IanJ on July 29, 2022, 01:49:22 pmThank you very much, I guess you are right, I am quite lucky in an unlucky situationLeaky capacitors are really the worst thing for the electronics and humans since the stink so much (smells like fish for me)

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 10:07:50 am
content: Quote from: HighVoltage on July 30, 2022, 09:18:24 amYou are sadly quite rightI can't argue with the age, since the Agilent 34401A is a quite old mesurement equipment too. One difference that might be game changing is the temperature and how close the caps are driven to the limit. I guess Agilent took a way chillier approach to bothBut maybe one of the experts here on the forum might be able to tell us exactly why

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 01:07:18 pm
content: Hello dear people of the ForumToday my parts have arrived and I successfully soldered them all up, pictures in the attachment.As usually some really really weird things have happenend. Read carefully now, I will write everything down as detailled as I remember 10 minutes ago. I went thrue every emotion there is, in these minutes, so bear with meAfter soldering everything up I took the other parts of the Keithley (Digital Board, Screen etc.) that are needed for testing and hooked them up loosely to the Analog Board. After verifying all the conncetions I powered it up and... somehow nothing on the screen.I panicked and pulled the AC plug out, checked for hot spots and took a deep breath, checked all the connections again and plugged the AC power in again. I watched the display closely and saw that the boot message (Keithley 2002, GPIB:xxx etc.) was on the screen for a short time every 3 seconds or so.I took the ADC board out and tried booting again and it worked fine. I ofcourse got the "Overflow" message everywhere but it booted fine.I inserted the ADC board, after shutting it down again, to measure the voltages. Then something strange happenend.I grabbed my phone to take a video. I pressed the on button and waited for the screen to flash away, but after flashing away I saw a voltage reading for theFIRST TIMEI was so happy that I didnt know what to doI knew that something is still wrong, because that isnt how keithleys normally wake up, right?Maybe the ADC board was not inserted fully the first time?I turned it off again and turned it then on, it started without a problem. I measured the voltage rails, which looked like this:+15V to VGND -> 12.7V+15V to GND -> 12.7V+15V to DGND -> 12.7V-15V to VGND -> -14.2V-15V to GND -> -14.2V-15V to DGND -> -14.2V+5V to VGND -> 4.91V+5V to GND -> 4.91V+5V to DGND -> 4.91VThe voltages are off by quite a bit, so there must be still a problem aroundI have checked the DCV and DCI functions and you can see the pictures in the attachment below. The seem to work fine for the range that I can measure and verify against. I ofcourse cant say anything to noise and stability but the readings arent that far off. But strangly when I switch the ranges myself I get a "Overflow" message, but when in Auto it mesures just fine, altought the voltage should have worked fine in my selected range.ACV seems to be completely off, I have tried to measure the 230V grid voltage, but it only shows about 150VAC. That is definitley not working correctly...I will later on post the error codes I am getting. Should I leave the device running or turn it off? I think it is about time to get my hand on a FLIR for this.Thank you all for helping out and the coming help that is still needed

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 01:45:18 pm
content: Here some pictures of the limited measurements that I can do :- Four voltage measurements compared to my Fluke 111.- One Current measurement against whats set on the Lab Supply.- One resistance measurement, short with wires...it measures negative resistance.- And one temp. measurement, this measurement shows nothing but I find the temp measurement option just cool.As I said the error messages will follow soon

author: alm
author_rank: Super Contributor
timestamp: July 30, 2022, 03:58:13 pm
content: Congratulations on getting it starting up and reading voltages!I would start looking further at the voltage rails, particularly the +15V is still way low. Look at the rails with a scope. Is there excessive ripple on the input of the linear regulator? Fixing the rails may well fix a bunch of self test errors.Keep a record about which tests are failing. Replacing a component and going from 20 failures to 15 failures is a nice measure of progress.

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 11:08:28 pm
content: Quote from: alm on July 30, 2022, 03:58:13 pmThank you, I am quite happyQuote from: alm on July 30, 2022, 03:58:13 pmI will try with the method, where I search for a heat source, because the voltages still arent quite in the range, that the Repair manual specifies. If that doesnt work out, I will try to go component, for component and find the defective component hopefullyQuote from: alm on July 30, 2022, 03:58:13 pmYou are absolutely right, sadly for me we are talking about 39 failuresThe arrors are to be seen below

author: SelectLOL
author_rank: Contributor
timestamp: July 30, 2022, 11:22:12 pm
content: So these are the erros that are currently popping up. The device is open without its cover and the measurement was done with the Rear inputs.200.2 A/D operation201.2 Testcal (Cannot measure 7V at A/D)202.2,4,6,8,10,12,14,16,18,20,22,24 Integration (Integration bit I15,14,13,12,11,10,9,8,7,6,5,4)302.4 ADGND MUX (Divider LO to ADGND)303.1 Input buffer (Input buffer)304.1 Open ckt ohms (Open circuit ohms)304.2 Open ckt ohms (2M open circuit ohms)305.4 20V range MUX (20V range MUX signal)306.1 Ohms (9.6uA ohms source)306.2 Ohms (1.92uA ohms source)306.3 Ohms (High ohms voltage source)307.1 100:1 divider (/100 input divider)406.6 Sample/hold (Sample and hold)410.1 TRMS (TRMS)411.1 TRMS filter (TRMS filter)411.2 TRMS filter (Filter)500.1 Amps/LO ohms (96uA ohms/200uA DCA range)500.2 Amps/LO ohms (960uA ohms/2mA DCA range)500.3 Amps/LO ohms (7.2mA ohms/2mA DCA range)500.4 Amps/LO ohms (20mA DCA range)500.6 Amps/LO ohms (200mA DCA range)500.7 Amps/LO ohms (2A DCA range)501.1 Amps protect (Amps protection)501.2 Amps protect (Amps bootstrap)502.1 ACA switch (AC amps switch)In total 39 errors. My main goal currently is to get the voltage rails to spec and hope that most of these errors vanishThe attachments contain pictures of the errors. If anyone has any other ideas, inputs or feedback are very welcomeThank you all

author: Kleinstein
author_rank: Super Contributor
timestamp: July 31, 2022, 07:35:16 am
content: The supply seems to use the same strange preregulator as the Keithley2001. So it makes sense to look at the transformer output voltage and the voltag after the rectifiers with a scope, to see if the regualtors have enough voltage to start with and if there is excessive ripple.A bad regulator is also a possible explaination, though not very likely. An oscillating regulator is also a possibility to get a lower votlage.Looking if something gets hot would be another point. If there is something drawing enough current to let the 15 V supply drop to 12.7 V this part should consume quite some power.An easy test would be to run the main board without the ADC card and check if the supply goes up/good.As long as the supply is not within acceptable limits the self test results are not really relevant. Especiall the 200.2 AD error could make most of the other tests fail.

author: SelectLOL
author_rank: Contributor
timestamp: July 31, 2022, 10:03:37 pm
content: Quote from: Kleinstein on July 31, 2022, 07:35:16 amThank you very much for the tip, I have used the available schematics for the 2001 to do my thinking.I have done some measurements, which confused me very much.Quote from: Kleinstein on July 31, 2022, 07:35:16 amI really hope that I can find something out with the temperature measurement. The Regulators for +15V and -15V get toasty (havent measured it but very hot to the touch, cant be right) even without the ADC board.I will sum up my current measurement and its results which confused me in the next replyThank you for your helpQuote from: Kleinstein on July 31, 2022, 07:35:16 amThank makes sense, without a good voltage many things might not work properly, I will just focus on fixing the voltages for now

author: SelectLOL
author_rank: Contributor
timestamp: July 31, 2022, 11:48:51 pm
content: Hello everyone, I hope you are all doing wellI have measured some points and of course it is as weird as it getsI started with the ADC board removed. I used the GND pin where the ADC board normally would sit for my ground. I measured:+15V -> 12.62V-15V -> -14.62V5V -> When the device bootlops its about at 4.18V and when it starts normally at 4.88V or 5.5V depending on how it feels. When I measured the 5.5V in the front from the "GND" that is labeled behind the ADC board. The capacitor which filters the 5V shows 4.95V, so I really wont be measuring from that stupid "GND" point behind the ADC board again.These measurements can be seen in the picture > VoltagesToGND_noADC.pngFor these I then switches to AC mode, to measure the noise > with the same time scale > NoiseSameTime_noADC.png and with a different time scale > NoiseFasterTime_noADC.pngThe +-15V rails seem really noisy to me, this is where my measurement of the voltage before the regulators come in handy.Everything can be seen clearly in the schematic attached, I have drawn in the voltages nicely.The voltage that comes into the rectifier for the +-15V rail shows me about 25.3VAC, which should mean about 35.67V peak to peak, minus about 1.4V means about 34.27V DC ideally, about with smoothing caps and real world application (I think) 32V (which still is not enough). I measured 29.1V.The testpoint HTP shows 14.26V and the regulators output voltage is at 12.62VThe testpoint KTP shows -14.75V and the regulators output voltage is at -14.26VAs far as I have understood the voltage needs to be about 2V higher than the desired output voltage. For both of these, this clearly isnt the case... Should I solder them out and measure the voltage without load?The bootstrap voltages look like this:+BS = 29.1V-BS = -28.9VInput AC = 25.3VACThe repair manual specifies atleast 34V so there must be also something wrong with that. The input AC voltage here is the same one as for the +-15V regulators.Last I measured the 5V supply which seemed fine for the moment. This measurements can be seen in the picture > 5V_Direct_noADC.png and > 5V_Direct_noise_noADC.pngThe testpoint JTP shows 5.4V and the regulators output voltage is at 4.95VThe incoming AC voltage is about 5.6VAC.I will also add the file where I wrote down the voltages and little notices for completion. I also want to add that when I hook up the ADC board doesnt change the values much, but I put it aside for now.I came to the the conclusion, that this will be a longer process than I thought, these little measurements took me hours. One reason being that the Keithley 2001 schematics use different Designators for the components and that makes it a little harder. I also double and triple checking my every move, because I dont want to fuck up thingsI will wait until I can hopefully lend out a thermal imager from someone, meanwhile if anyone has any idea what I should measure next, tips and feedback are very welcome. Thank you all

author: picburner
author_rank: Frequent Contributor
timestamp: August 01, 2022, 06:39:29 am
content: Since all the voltages are below the limits, as Kleinstein has already told you, it most likely schould depends on a fault in the pre-regulator circuit (I hope for you that it is this and not the electrolyte leaking from the capacitors that does electrolysis frying under some IC).Check that at the transformer primary (black and brown wires) is 230V ac.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 01, 2022, 07:47:32 am
content: With the preregulator the waveform is no longer a clean sine. So the fator of 1.4 for peak to RMS voltage no longer applies. The voltage after the rectifiers still looks a little low, but there is ripple and if the transformer is heavily loaded the peaks go down first.The question here is if this due to a failure in the preregulator or overloading the transformer in some way (this could be even on the display board).It would help to measure the AC voltage of a transformer secondary with the scope. Here one could see the waveform and likely also if the MOSFET in the preregulator actually is operating.With the voltage rather low the control signal to the MOSFET should be constantly active, trying to provide the maximum voltage.Measuring at the mains input side needs extra care. Except for maybe a careful check with a good (handheld) DMM this should only be done with the DMM power through an extra isolation transformer.

author: SelectLOL
author_rank: Contributor
timestamp: August 01, 2022, 10:38:53 am
content: Quote from: picburner on August 01, 2022, 06:39:29 amYeah I just realised now what Kleinstein meant by pre-regulator, I should have measured the left side of the schematicI see now. Ahahahaha that stupid electrolyte shall stay away from me, lets hope for the bestQuote from: picburner on August 01, 2022, 06:39:29 amI have quickly checked it with my Fluke Multimeter, it says 180VAC. hmhmhmhmhm not that optimal right?Thank you for your reply

author: SelectLOL
author_rank: Contributor
timestamp: August 01, 2022, 10:46:15 am
content: Quote from: Kleinstein on August 01, 2022, 07:47:32 amOh interesting so my math wasnt right, but there is still something very faultyQuote from: Kleinstein on August 01, 2022, 07:47:32 amWhen I read your last reply I hadnt understood what the preregulator really is and thought that it is what I was measuring. Now I clearly see that the preregulator part is on the left before the transformator, I hadnt seen that, that part has an importance, thank you for thatI will measure the preregulator out really carefully with the scope and see where I might get an isolation transformer, if not I will cut off the Earthing part of the scopes cable (safety second I guess)Hopefully I can do that measurement today or tomorrow. Thank you very much for your help

author: Kleinstein
author_rank: Super Contributor
timestamp: August 01, 2022, 12:30:51 pm
content: For the start there is not need to use the scope on the primary side. One can quite a lot by looking at the waveform at the secondary side of the transformer: the waveform should be essentially the same.It is not a good idea to seprate the ground on the scope - better wait for an isolation transformer to do the measurement in the right, safe way, with the DUT powered trough the transformer and the scope still grounded. This still needs care as the transformer defeats the GFI and the scope provides a path to ground.Getting less than 230 V for the transformer primary is normal, though 180 V may be a little on the low side. The part with the rectifier and MOSFET is there to reduce the voltage so that the linear regulators don't see much more votlage than needed to maintain a stable supply. One possible fault may be the MOSFET never turning on, e.g. with a bad optocoupler or an error on the secondary siden.With the current low voltage the The CONT signal should be constant low and thus a signal to turn on the MOSFET. When properly working there should be a 100 Hz PWM like signal, providing the full power for something like the forst half or a little more of the main waveform and than turn off.

author: SelectLOL
author_rank: Contributor
timestamp: August 02, 2022, 06:05:49 pm
content: Quote from: Kleinstein on August 01, 2022, 12:30:51 pmThank you for your reply. I now have watched some videos related to the Keithley 2001, that I know the similarities in the PSU part from you. Marco reps's video had show a blown out 470Ohm Resistor parallel to the MOSFET. Well looks line mine is broken tooMarco reps's video :https://youtu.be/HVDQeJTEHFI?t=330Amazing video from IanScottJohnston :https://youtu.be/S8okMaAKYiw?t=1503I have attached a picture which shows the broken resistor. I was currently doing the thermal measurements which didnt show me anything too suspicious. That being said the Flirs E5's resolution isnt that high, even with the overlay of the real image it is really hard to see anything. I guess I will revert to the good old measure and find methodI will post some of the thermal images later onThe broken resistor is probably related to the bootlooping problem. It probably turned on many times slowy until some capacitor was charged up enough to get the full cycle going. I hope to find a similar resistor to continue my measurementsI will try to power the unit on again without it, I mean it worked already when it was open circuit right

author: SelectLOL
author_rank: Contributor
timestamp: August 02, 2022, 07:29:19 pm
content: Alright everyone its me again, I hope all of you are doing all right.I have done some temperature measurements with an Flir E5 which, I was able to borrow. The pictures are attached below as a zip, because it has one thermal image together with an actual image from the camera. The file limit is sadly 10 files per postWith the thermal imager I saw that the resistor (Ke 2001 R100 near MOSFET) didnt radiate much heat itself and becuase I watched a video from marco reps as I told earlier, I thought it might be a good idea to measure it out. It definitely was an good idea to check it out, since it was broken(see last reply)Fast forward. After I took the images I sat down an studied the pre-regulator a bit. I wanted to measure it out definitly.For the measurements I took my Fluke handheld DMM which is powered with a battery.I thought that might be the safest bet. I measured a little and saw a 4.3V volatage at pin 1, where 5V should be present. So I thought that my GND point wasnt that good and tried to search for a GND on the IC. When I came to pin 6 where the Gate of the MOSFET is connected, the transformator which wasnt screwed down started to make brumming noises (When measuring between Pin 1 and Pin 6). Of course I went away and then did it again to verifiy that it comes from me and it indeed did. I should have studied the datasheet of the IC, I thought that they put the supply voltage on a diferent part of the schematics to make everything look clean, but it seems, that it just doesnt have a supply voltage. Just as seen on the schematic symbol, it has diodes, not more, not less.Well the aftermath now is, that the MOSFET isnt getting hot anymore and probably has a short. The voltage between Brown and Black for the primary is about 220VAC, 40VAC higher than before. The output of the voltage regulators for +-15V are bang on thoughI cant measure for a long time, since the regulators are getting hot pretty fast (about 80 degrees in 2-3 minutes) and I didnt dare to let them get hotter.I probably will have to solder out the optocoupler (Ke2001 U100, Ke2002 U101) and see what comes in from the CONT signal and what lies at the MOSFET Gate. When I do that, I can decide on what I need to buy again.Thanks everybody and I wish you a good day/night.The first 4 pics are before the short and last 4 are after short, these are eye candy for visitorsThe zips contain the images with the timestamps so one can see the heatup over time.

author: SelectLOL
author_rank: Contributor
timestamp: August 02, 2022, 07:31:44 pm
content: The zips :

author: Kleinstein
author_rank: Super Contributor
timestamp: August 02, 2022, 09:11:33 pm
content: The U100/U101 opto-coupler is a photovotaic type: at the output it can produce power like some solar cells, usually some 5-10 µA and 6-8 V maximum. This is just enough to drive the MOSFET gate, but not much more.The optocoupler could be a source of error, if the current is no longer enough (e.g. the LED inside getting weaker).Getting enough voltage with the broken MOSFET point towards a problem with the pre-regulator part in some way.Having only a 4.3 V supply for the optocoupler (output of U619 in the K2001 schematics) would suggest that there is a problem with the diode or capacitors (e.g. no contact for C625 in K2001 plan) for the charge pump, or maybe an oscillating 5 V regulator.

author: Per Hansson
author_rank: Unknown
timestamp: August 02, 2022, 10:36:48 pm
content: Quote from: SelectLOL on August 02, 2022, 06:05:49 pmQuote from: SelectLOL on August 02, 2022, 07:29:19 pmThank you so much for the link to those videos, I was reading the schematic yesterday but could not understand how in the world the circuit works, the explanation in both videos really cleared it up!That said I think your conclusion about you shorting out the MOSFET is wrong:Since your R100* was completely open the only logical explanation for why the meter turned on at all was that the MOSFET Q528 was already shorted.Otherwise it should have behaved like in Marco Repos video and just remained off: Because U100* is powered from the secondary of the transformer via resistor R100...* = Keithley 2002: R101/U101 instead

author: SelectLOL
author_rank: Contributor
timestamp: August 03, 2022, 08:35:58 pm
content: Quote from: Kleinstein on August 02, 2022, 09:11:33 pmThank you for your reply, I have now measured out the opto-coupler and am surprised to say, that it still seems to work just fine. I have desoldered it and measured it out by applying DC voltage to the LED and measuring the output. As to be seen in the attachments.I measured about 1.25V @ 11mA for the LED, which is OK according to the datasheet (also attached, altough B version insted A). The Output was around 9V unloaded (Just Scope). Should I still order a new one?I got less luck with the MOSFET, it seems to be totally shot. I will have to replace it, which is quite easy to do. The 10W 470Ohm Resistor is a little harder to find, but I still managed to find some similar things. I will post my basket later onQuote from: Kleinstein on August 02, 2022, 09:11:33 pmI had a hard time finding U619 but wow I saw that, that part is on the digital board side, which I can easily measure out when my parts are bought and arrive.

author: SelectLOL
author_rank: Contributor
timestamp: August 03, 2022, 08:53:09 pm
content: Quote from: Per Hansson on August 02, 2022, 10:36:48 pmThank you for your inputI always try to post as much info as possible, so that when someone else might see the post with his broken Keithley, has an easier timeI attached 2 zip folders called beforeShort and afterShort (2-3 replies ago), which contain all the thermal images. Both also include closeups of the MOSFET. Before my accident with the FET it showed me about 60°C and we both agree on, that the Resistor didnt radiate any heat for both times.You say that the FET was always shorted, then why did I measure only 180VAC across the primary before and now 220VAC?Where does the temperature difference come from? My guess would be, when it was working normally it had a decent voltage drop over it and created plenty of heat. Now that its shorted, it just doesnt drop any voltage and thus any heat. But when it always was shorted, how would that work?You are right about Marco Rep's case, that might show another fault in my Keithley which we yet have to findI will measure out the MOSFET extensively tomorrow, to see if it really is broken and post again

author: Per Hansson
author_rank: Unknown
timestamp: August 03, 2022, 09:41:43 pm
content: Quote from: SelectLOL on August 03, 2022, 08:53:09 pmIt's possible it was not completely dead, the MOSFET is rated for operation with 20v on its gate with transients up to 40v. (I've attached its datasheet).I don't understand how connecting a 11Meg resistor (inside your handheld meter) between +5v (4.3v) and the MOSFET's gate would destroy it?Quote from: SelectLOL on August 03, 2022, 08:53:09 pmI just had a thought about the transformer primary:It works exactly like a variac, and they have an interesting behavior:A "good for bench use" variac will have 5 terminals, these allow you to get higher than your line voltage.I don't have such a fancy variac, mine only has 3-terminals but if I'm careful I can still simulate this:I brought the variac to 92% and then I hook the live wire up to the wiper terminal.Now when I measure between neutral and wiper I obviously have my line voltage: 240VAC.But the interesting part is if I measure from neutral to the now unconnected terminal of my variac: 260VACTherefore when you measure from the BLK to BRN terminals and get a specific voltage reading I guess you will have no idea which way the Hi/Lo relay K100 is connected!An example is if you would input 180v between the BLK/WHT & BRN/WHY wires you would read 240v between BLK & BRN.And further if you would input 90v between the BLK/WHT & WHT wires you would still measure the same 240v on BLK & BRN terminals?Further complicating matters is the current limiter through CR100, that can be anywhere and it will make all readings confusing at best!P.S: It's completely possible I'm wrong but then I hope someone will correct me!

author: TiN
author_rank: Super Contributor
timestamp: August 04, 2022, 12:44:09 am
content: I think you probably jumped the train soldering new parts. From your previous photo it looks like you are in full treat with leaked electrolyte. So ALL components from area around 5cm in each direction from where cap was must be desoldered, cleaned with IPA, all PCB via's soldered thru, and cleaned again with Acetone, then distilled water, then IPA again, dried, cleaned again. Then put new parts back in. This procedure is mandatory for any old (15+ year old) Keithley 2001/2002, unless you want to continue "repairing" it till cows come homeI have old video on my kei2002_u2 unit from 2016. This should show you the process. I still have this very meter, and it's happily calibrated and used as my daily bench meter.

author: Zucca
author_rank: Unknown
timestamp: August 05, 2022, 02:02:27 pm
content: Excellent Job SelectLOL.Please check thishttps://www.eevblog.com/forum/repair/this-keithley-2001-need-to-be-saved!/msg2883864/#msg2883864before ordering a new R100 which is difficult to find anyway... such a unicorn...I do not like thermalfuse, and I would avoid them....

author: SelectLOL
author_rank: Contributor
timestamp: August 05, 2022, 09:22:09 pm
content: Quote from: TiN on August 04, 2022, 12:44:09 amHello TiN thank you for joining in. I have seen most of your videos and whats on your website, amazing work, thank you alot for thatI am guessing that the caps have already been replaced once, besides one that somebody deemed to not be worthy to replace. When my new parts arrive (MOSFET and Resistor) I will do what you said to the parts close the Capacitor that leaked. And after that I can continue with my measurements to find more defective stuff.

author: SelectLOL
author_rank: Contributor
timestamp: August 05, 2022, 09:50:38 pm
content: Quote from: Zucca on August 05, 2022, 02:02:27 pmThank you, thank you but the job is still to be doneLuckliy I have so many awesome contributors here, I am quite confidentQuote from: Zucca on August 05, 2022, 02:02:27 pmAmazing, I have read the whole thread, it was as funny as it getsWhat is the current status of your device, did you manage to clear every error? Is the resistor you installed holding up fine?And to the Resistor, I have seen that stupid thermalfuse on marco reps's video:https://youtu.be/HVDQeJTEHFI?t=344. And luckily I have ordered the exactly same resistor as you did, I say luckly because when it worked for you, it hopefully will for me tooMarco reps didnt go into detail which resistor he has used for his repair in the end. But athttps://youtu.be/HVDQeJTEHFI?t=432one can clearly see that he had the same ideaThe digikey link for the resistor R101 Ke2002:https://www.digikey.ch/de/products/detail/ohmite/HS10-470R-J/5307525I had to put a little more thought to replace the MOSFET Q101 Ke2002. The obvious parameters like cont. Current, max. Wattage etc. were easy to sort and chosse from for the right part. But I was afraid of the driving range of the feedback circuit that drives the FET. I chose 2 FETs with similar input voltage sensitivitys to test. My thinking might have gone over the board, but Id rather be caucious and select the right part (or buy two/many) to not delay the repairSo the links to the ones I bought:https://www.digikey.ch/de/products/detail/taiwan-semiconductor-corporation/TSM13ND50CI/9602845andhttps://www.digikey.ch/de/products/detail/alpha-omega-semiconductor-inc/AOTF12N60L/6946477I will test the first one first and if it seems to be operating fine, I wont bother to change it for the other one.The parts will probably arrive Monday and the journey will continue thenI will keep you all updated, thank you all very much

author: Zucca
author_rank: Unknown
timestamp: August 06, 2022, 02:14:35 am
content: Quote from: SelectLOL on August 05, 2022, 09:50:38 pmIt was fixed before I moved to USA. Once I will setup my lab here in USA properly, I will let you know if it is still okay.I need to do a calibration anyway....Yes the power resistor without thermalfuse I got is simply perfect, even the size is perfect!

author: Per Hansson
author_rank: Unknown
timestamp: August 06, 2022, 09:28:21 am
content: Quote from: SelectLOL on August 05, 2022, 09:50:38 pmJust a note on the MOSFET, the most important specification in this implementation is not RDS(on) or the max Drain Current (Id) you can go with much better values than the original and it will not cause problems.What is important is that the Gate Charge in Columbs (nC) is similar, because that is how much drive is required for the device to switch, which is of course matched to the U100/U101 photovotaic opto-coupler's drive strength.And following that the important parameters are the actual switching voltage (Vgs th).Just doing a quick search on Mouser I found these ones in stock: Vishay SIHF30N60E-GE3 and Infineon IPA65R045C7XKSA1 where the latter seems like the best match.Also worth keeping in mind these are physically smaller than the original package, but maybe that is not a problem, the proper package would be TO-247 but I think the availability of an isolated MOSFET in that package is much less...

author: SelectLOL
author_rank: Contributor
timestamp: August 08, 2022, 07:28:56 pm
content: Quote from: Zucca on August 06, 2022, 02:14:35 amAh amazing, I wish you all the best setting up the lab thereMine came today it is really a good fit, smaller than I expected. I will be posting some pictures later on.

author: SelectLOL
author_rank: Contributor
timestamp: August 08, 2022, 07:52:08 pm
content: Quote from: Per Hansson on August 06, 2022, 09:28:21 amThank you very much, thats exactly what my seniors told me too. The Gate Charge and Vgs are very important. I have had a look at your MOSFETS, the latter one to be specific is the one, which I will do a little overview with:ValueVishay SIHF30N60E-GE3TSMC TSM13ND50CIOriginal 2SK1451Vgs th.2.8V3.8V2V-3VGate Charge85nC @??V39nC @10V???nC @?VThe table above shows a little comparison between the one you recommended, I bought and the best I could find for the original FET from left to right (pdfs attached).The Vgs voltage of the one you recommended seems to be good, would you say mine wouldnt work as well/is out of range? When buying I compared with the output of the opto-coupler, which seemed to be able to drive even much larger FETs perfectly fine. Should I stick with my FET or change it?The package for my current one fits pretty fine, it smaller then original but its shape is identical, so it presses nicely against the wall of the Keithley.I will make a post to what happenend when I started up later on. Thank you very much again

author: SelectLOL
author_rank: Contributor
timestamp: August 08, 2022, 08:06:44 pm
content: Hello everyone, here is the latest update to the threadMy parts have arrived and I already soldered them in. Pictures in the attachments.The Ke2002 booted just fine as expected. Without the weird bootlooping, that I had before.Currently I dont have the Flir on my hands, I will have to lend it out tomorrow again. I measured a little with a temperature probe and the FET and Resistor seem to be at ambiente. The Regulators are a little hot, about 65°C, but I couldnt measure it accuratly.I have measured the +-15V rails and they seem to be bang on. About +-150mV difference and totally in spec.I dared to do a self test for funsys, the errors are as following:401.1 Regulator405.2 Abs ckt. *10405.4 Abs ckt. *10405.6 Abs ckt. *10406.6 Sample/hold409.6 /500 freq cmp410.1 TRMS411.1 TRMS filter411.2 TRMS filter500.7 Amps/LO ohms600.2 Ohms senseWe have gotten rid of some of the errorsTomorrow I when I have the thermal imager lend out, I will measure out the pre-regulator again an oversee the temp. of the regulators. When I am assured of all the voltage regulation, I will start tackling other problemsTo be fully hones, I tried to measure it out again with my Fluke DMM and when measuring between pin 4 and 6 where the output is, the transformator brummed again. This time though it probably didnt break againThank you very much and I wish you a nice evening/morning/midday

author: Per Hansson
author_rank: Unknown
timestamp: August 08, 2022, 08:24:48 pm
content: Quote from: SelectLOL on August 08, 2022, 07:52:08 pmI used the MOSFET from the Keithley manual part list: Motorola MTG9N50E (I attached the datasheet) when looking for replacements.This is quite allot better characterized than the (what I assume is a Sanyo) 2SK1451 that your unit apparently had installed.That said the most important characteristic is missing from it, but it really seems quite similar if you eyeball it from the graphs:

author: Kleinstein
author_rank: Super Contributor
timestamp: August 08, 2022, 08:57:27 pm
content: The gate charge has 2 components:1) the gate capacitance times voltage change at the gate (e.g. 5 or 10 V)2) the gate to drain capacitance times the drain soure voltage.With higher voltage (e.g. > 50 V) the 2nd part is often the dominating part. For the charge specs on also has to look at the conditions: one gets a higher gate charge with more drain voltage. Especially with modern parts the tricky part is that the drain capacitance can be quite nonlinear. So Crss changes with voltage and gets quite a bit smaller with higher voltage. Modern parts got better be reducing Vrss at higher votlage.If there are no gate charge specs, one could still use Crss as a crude alternative parameter, but whatch out for the conditions. If the curve is given one could integrate the area to get the charge.With some 10 µA of current from the coupler and some 50 nC the switching speed would be some 5 ms, so rather slow, even compared to the rather low frequency (100/120 Hz).

author: SelectLOL
author_rank: Contributor
timestamp: August 20, 2022, 08:38:18 pm
content: Hello everyone, I hope you all are doing fineIt sadly took a little longer than I wanted to post a new update.But dont worry, I was not doing nothing! First of all thank you Kleinstein and Per Hansson for the replies related to the Pre-Regulator FET. If it really seems to be a problem, I will switch it outIn the meanwhile I bought a thermal imager that has a little bit more resolution that the Fluke I was using. And I was in the search of an isolating transformator for my measurements.When I got my hand on both I started measuring with my Scope. I used my 4-CH Hantek with 1GS/s and wasnt pleased with the resolution in roll mode over >10 seconds.So I tried fixing my LeCroy, which was out of service since I tried to switch from an HDD to an SSD. I reverted all my changes and got it back running.I will post both the oscillograms of the Hantek and LeCroy scope.I am still trying to figure out the Pre-Regulator, because it still doesnt seem to operate correctly as far as I can tell.Lets start with the oscillogramms from the Hantek. In the picture (Ke2002_Pre_Reg_Meas.png) one can see what Channel and Color corresponds to where I measured. All referenced from the Source of the Control FET (Q608 Ke2001 schematic)Since I dont have a differential probe to seperate my ground I couldnt measure the Control FET out together with the Pre-Regulator FET. Thats why I put 2 oscillogramms together in one picture. The blue signal is the Gate Voltage of the Pre-Regulator FET referenced from its Source.And now the same measurement with the LeCroy. Since it has a higer sample rate of 2.5GS/s and more memory, I was able to save the 3 Signals and measure out the fourth in one oscillogramm. I even was able to zoom pretty hard into the Gate signal of the Pre-Regulator FET as to be seen in the oscillogramm below. The measurement points are the same and are labeled directly on the LeCroy.As far as I can see, after a while the Pre-Regulator seems to be getting its 100Hz like signal that Kleinstein mentioned. The problem is, that I really can't see the signal coming from the FET that controls the CONT line. How can that be? Is it working correctly?If anyone wants me something to be measured out differently, I can do that without a problem now with the isolating transformerFor the thermal imaging, one part is getting pretty toasty. It is labelled U108 and is located behind U107 and U109 (-15V and +15V) regulators. The U108 is an +5V regulator, same as the U110, why are there 2 of them? (page 19 Ke 2002 repair manual)As far as I can tell the the similarities to the Ke2001 end there, since it doesnt have the same part in the same place as the Ke2002. Does anybody know what it supplies voltage to?The thermal images show its temperature, it gets over 85°C in about 2 minutes.Thank you all very much and greetings

author: saturnin
author_rank: Regular Contributor
timestamp: August 22, 2022, 09:04:50 am
content: Quote from: SelectLOL on August 20, 2022, 08:38:18 pmThe pre-regulator in K2002 works in such way that it maintains voltage on C611 (big axial capacitor on the digital board) vey close to 7.50 V (the voltage is quite stable due to large capacitance of C611). If the voltage on C611 is correct, it is likely the pre-regulator works fine.You previously reported +/-15V rails on the analog are in specs, is it also true for +/-BS voltages?

author: IanJ
author_rank: Unknown
timestamp: August 22, 2022, 10:17:12 pm
content: If you look at the last 5 minutes of Part 5 of my Keithley 2001 repair video, and the Part 6 video I explain how the pre-regulator works including how the CONT line operates and demonstrate how to test the various parts with an LED, multimeter, DC PSU and variable transformer.Ian.

author: SelectLOL
author_rank: Contributor
timestamp: August 23, 2022, 07:51:50 pm
content: Thank for the reply saturnin and nice observation of the 7.5V!I measured the BS voltage from -BS to +BS and it shows around 38.7V which is a little over the maximum and over where it should beI physically measured here (first pic).With the multimeter I measured some little jumps of the voltage rail, so I hooked up the scope and the voltage can be seen on the little gif I made. And of course a static image for a quick view.The average voltage of the highlighted window can be seen under the Measure tab. It is weird that it tries to ramp up and then down again. Weird behaviour, something isnt right

author: SelectLOL
author_rank: Contributor
timestamp: August 23, 2022, 08:07:01 pm
content: Hello Ian Thank you for your reply. I watched your videos only until the 5. video and sadly only to where you explain the circuit and didnt even know that there is a 6. videoTomorrow I will hopefully set up the circuit the way you did and try to measure out the Gate of the FET for CONT and apply some voltages to where you also did to see how it reactsYou bridged some relays for your device, how is it holding up? I am quite temped to just do the same

author: IanJ
author_rank: Unknown
timestamp: August 23, 2022, 09:43:02 pm
content: Quote from: SelectLOL on August 23, 2022, 08:07:01 pmThe circuit is a clever design, but sadly it's not a great nor a particularly robust design. One small issue with the 120/240vac switching or even the pre-reg and it's goodbye just about every IC......hence why my digital board was a complete mess!My 2001 is working great with the relays by-passed. However, I don't think you are at that stage yet.......I would test the CONT signal per my video first, easy and safe to do with no AC voltages involved........and move on from there.Ian.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 25, 2022, 06:52:11 am
content: Bypassing the 110/220 V relay may be a good idea. It is a clever design to automaticly decect, but if the detection fails and uses the 110 V setting with 230 V this is quite some stress. Bridgeing that relay is more reliable than the automatic detection and thus more like a safe option and you only loose the 110 V use option that is not relevant in Europe.