hybridfree/eevblog-posts huggingface dataset:
Fluke 87v broken display - Page 1
Forum section: electronics / repair

author: jerryk
author_rank: Regular Contributor
timestamp: December 12, 2024, 10:24:24 pm
content: In a not so smart moment I managed to crack my 87V display. Fluke will repair it for near the price of a new one. There are these $16 displays on Ebay and a three star reviewed display on amazon. Is there hope? Has anyone managed a display replacement successfully and want to share any source information for a replacement display?I'll keep holding back the tears.Jerry

author: mwb1100
author_rank: Frequent Contributor
timestamp: December 12, 2024, 11:33:12 pm
content: I haven't technically replaced an 87V display, but I have removed/reinstalled one in order to clean the zebra strips to fix a "missing segments" problem.Pretty easy procedure; plenty of youtubes to demonstrate.I haven't experience with the Chinese eBay LCD offerings, but LCD technology is hardly rocket science so I'd expect them to behave just fine. And $16 isn't too large a gamble.There's a seller on eBay who sells what he claims are original Fluke parts - I have little reason to doubt it - for $40 (including shipping):-https://www.ebay.com/itm/266136252993(I would have sworn I've bought parts from this seller, but I don't get a "you've bought from this seller" note when I go to that item's page; however any dealing I might have had would have been more than 5 years ago).I'm not sure what used 87v's go for today on eBay, but if you don't want to go the replacement route - or you replace and don't like what you see - you could likely sell yours on eBay for a decent amount (even with the broken display) and use those proceeds to supplement buying a new meter to reduce your out of pocket to far less than what Fluke is asking to fix yours.

author: jerryk
author_rank: Regular Contributor
timestamp: December 17, 2024, 01:50:41 am
content: The reseller linked above was great. Note the dates between this post and my first post. Very fast replies and the shipping to Alaska got here in record time. Replacement was a success! The reseller even included a little green case with the display. Whether the $16 display would have worked is immaterial to me. I'm happy to have my 87V back.I am a bit blown away at the durability of the 87V because I did my best to crush it. I pinched it between the cab of a large skid steer and the main frame. When I could not get this heavy cab to come down all way I lifted it back up an then slammed it back down over and over till I looked around the side of the cab and saw my poor 87V wedged in by the hinge point. Not sure any other multimeter would have survived.Thanks for the help - Jerry
Fluke 87V case front replacement - Page 1
Forum section: electronics / repair

author: panamaszr12
author_rank: Newbie
timestamp: December 17, 2019, 05:33:56 am
content: I have a fluke 87V with the lettering gone on the front case. I ordered a new case front, but need to know how to remove the rotary dial to put on the new case. Any help would be appreciated.Thank you in advance

author: Black Phoenix
author_rank: Super Contributor
timestamp: December 17, 2019, 10:09:26 am
content: You can use the service manual for instructions:http://doc.xdevs.com/doc/Fluke/87V/Fluke_87V_Multimeter_Service_Manual-Fluke87servicemanual.pdfFor what I see is the same kind as most of the Flukes, so you need to take out pressing the centre pin (credits toMr. ModemHead- Shown on a 170 Series)
Fluke 87V-Ex, wrong temperature reading - Page 1
Forum section: electronics / repair

author: xavier60
author_rank: Super Contributor
timestamp: February 18, 2020, 03:17:38 am
content: I recently bought the DMM on ebay. Every thing seems to be fine except for the temperature range.It reads 188°C rather than the expected 25°C when I plug in a K type probe or just short the test probes.Does anyone know how to deal with this?
Fluke 87V Repair - Page 1
Forum section: electronics / repair

author: Dave G
author_rank: Newbie
timestamp: March 30, 2020, 05:15:09 pm
content: My trusted Fluke as failedOn AC 240Vac it shows 240mvOn Dc 1.5vdc it shows0.15vdcCould anyone point me in right direction. Looks possibly like a range resistor fault but why would a resistor just fail ??any advice appreciatedThanks Dave

author: retiredcaps
author_rank: Super Contributor
timestamp: March 30, 2020, 06:31:02 pm
content: Some suggestions/questions.1. Have you recently had an "oops" moment with some high energy event?2. Did you lend it out to someone?3. Try a fresh new 9V battery.4. What do get when you measure a 1km ohm resistor?5. Have you recently opened the meter to change a fuse or battery?6. Are you the original owner and did you buy the meter from an authorized dealer?

author: Dave G
author_rank: Newbie
timestamp: March 31, 2020, 09:59:52 am
content: No oops moment that I know ofYes its been mine since new from RS1Kohm=1KohmNot lent outBattery Good

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 31, 2020, 12:43:12 pm
content: Fluke will fix it for free.In the U.S. they typically ignore their own stated policy regarding authorized dealers and fix anyway.I'm assuming "RS" is your authorized dealer. If they won't give you satisfaction, contact Fluke directly for options.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 31, 2020, 08:03:15 pm
content: Quote from: Dave G on March 31, 2020, 09:59:52 amI suggest following mzacharias suggestion of contacting RS Components or Fluke for a repair/replacement under warranty since you are the original owner.
FLUKE 87V Resistance Issue - Page 1
Forum section: electronics / repair

author: zker666
author_rank: Contributor
timestamp: January 26, 2025, 03:21:09 am
content: I rescued this 87V out of a bin of rejected multimeters doomed for the dumpster. It was the nicest one out of the bunch and appeared mostly functional. Indeed, most functions and ranges are working and accurate to my other meters, except for the resistance range. A constant 14-15M resistance is displayed with no input. Standard procedure, cleaned inputs/selector switch with deoxit/ipa, nothing. The board is clean, and no evidence of battery corrosion or other foreign substances around the input or anywhere else on the board. Measured RV1-3, >100M, all diodes are intact.Seems to be nothing visually wrong at all, any advice would be helpful.

author: zker666
author_rank: Contributor
timestamp: January 26, 2025, 03:21:44 am
content: Board Views.

author: bdunham7
author_rank: Super Contributor
timestamp: January 26, 2025, 03:44:37 am
content: I think the next thing to do is desolder and remove the input jack assembly, or if that isn't easy for you perhaps remove the fuses and dunk the bottom 1/4 of the board in IPA for a few hours and then gently bake the board at 50-60C for 24 hours or so.

author: floobydust
author_rank: Super Contributor
timestamp: January 26, 2025, 04:13:44 am
content: It's usually the MOV's or clamp-transistors that are damaged and are leaky.

author: zker666
author_rank: Contributor
timestamp: January 27, 2025, 02:37:49 am
content: Quote from: floobydust on January 26, 2025, 04:13:44 amThis is my guess as well, but all pertinent components on the input measure OK in-circuit. Next step is to remove the MOV's and protection diodes until I get an open I guess. No reason in removing the input jack assy, I'm certain there is a slightly sickly component somewhere in the input section. Still a free 87V though

author: floobydust
author_rank: Super Contributor
timestamp: January 27, 2025, 03:11:30 am
content: Hey it's a great dumpster divefor ref. 87V schematic of the input section here. CR8, CR9 BAV199 to check as well.
Fluke 88 Flickering and Staying on - Page 1
Forum section: electronics / repair

author: hpmaxim
author_rank: Regular Contributor
timestamp: August 07, 2023, 12:15:42 am
content: I have what seems like a weird problem with a Fluke 88 (I suspect this is pretty similar to the Fluke 87). The display (and sometimes the backlight) will flicker on/off when I rotate the selector knob. In some cases, it'll actually stay on when in the off position. It usually settles down pretty quickly when you take your hand off the knob, but occasionally you have to physically poke at or tweak the knob a bit to get it to actually shut off. Any idea what the cause is or how to correct it?

author: retiredcaps
author_rank: Super Contributor
timestamp: August 07, 2023, 03:44:52 am
content: Dirty tracks on range switch?http://mrmodemhead.com/blog/fluke-83-dmm-repair/http://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/Lots of other ideas on his site as well as the 2 above.

author: hpmaxim
author_rank: Regular Contributor
timestamp: August 07, 2023, 05:59:25 am
content: It looked very different than described. The backside seems to be the PTF layer they described. However I saw no white disc, it was just that thing on the front. It looked like there was a plastic/metal disc but I couldn't get it clear of the assembly to get it out. Maybe I could have but it looked like it would be easy to damage if I tried to force it. I was able to get some dirt off the front but it's not clear that I got anything off the back. I cleaned it with isopropyl as stated.The black disc on the back doesn't want to go back on -- and I'm not sure how it's supposed to be aligned (not that I can even get it in). I took it off with popsicle sticks, and it just kind of flew off. Looks undamaged but still won't go back on.Any ideas?

author: hpmaxim
author_rank: Regular Contributor
timestamp: August 07, 2023, 06:20:17 am
content: Key to the mystery was: "I took it off with popsicle sticks and it just kind of flew off." Apparently, there was another little plastic piece that went through the center that also went flying and that I didn't see. Found it on the ground next to me and was able to get everything back together pretty easily. Seems like it's fixed now. Who knows for how long.
Fluke 8808A Pantalla con poco Brillo  - Page 1
Forum section: electronics / repair

author: keko
author_rank: Newbie
timestamp: December 10, 2021, 02:54:42 pm
content: Hola Amigos.Compre un Fluke 8808A por Ebay - USA de segunda mano, fue enviado a Chile muy bien embalado, lo estoy probando y está funcionando bien, pero la pantalla tiene menos brillo que la del Fluke 45, además cuando mido Diodos no emite un sonido como el Fluke 45.¿Amigos es Normal lo que ocurre con la pantalla con poco brillo y la medición de diodos sin sonido?, ¿es posible configurar el brillo de la pantalla y activar el sonido al medir Diodos?Agradezco su ayuda y orientación con mi Fluke 8808A

author: tunk
author_rank: Super Contributor
timestamp: December 10, 2021, 03:05:05 pm
content: English please - maybe you could use google translate?

author: keko
author_rank: Newbie
timestamp: December 10, 2021, 03:09:03 pm
content: Thank you very much for your reply ... Excuse my English!Hi friends.I bought a second hand Fluke 8808A by Ebay - USA, it was sent to Chile very well packaged, I am testing it and it is working well, but the screen has less brightness than the Fluke 45, also when I measure Diodes it does not emit a sound like the one on the Fluke 45.Friends, is it normal what happens with the screen with low brightness and the diode measurement without sound? Is it possible to set the screen brightness and activate the sound when measuring diodes?I appreciate your help and guidance with my Fluke 8808A

author: gamalot
author_rank: Super Contributor
timestamp: December 10, 2021, 03:18:26 pm
content: QuoteYes.QuoteNo.

author: keko
author_rank: Newbie
timestamp: December 10, 2021, 03:31:17 pm
content: Thank you very much Friend for your answer.I've had the Fluke 45 for a long time, it's an excellent piece of equipment. My New Fluke 8808A arrived and I am learning its functions.Greetings from Chile
Fluke 8808A - Page 1
Forum section: electronics / repair

author: hitecelec
author_rank: Regular Contributor
timestamp: February 06, 2020, 12:45:51 pm
content: Hi folksFluke 8808A does not read DC/AC voltages, however Ohms and dc current ranges are functionalAny clues? or schematicsThanks in advanceAnand

author: hitecelec
author_rank: Regular Contributor
timestamp: February 06, 2020, 01:14:37 pm
content: hellolooks like it is a similar problem posted about auto range posted in this group previously

author: goaty
author_rank: Regular Contributor
timestamp: February 06, 2020, 02:56:49 pm
content: Looks like input circuitry. If Ohms can measure and amps and all UI is working it maby is only fuse or input resistor divider / switching (relay) and protections (MOV, fiuse,etc) or corroded track/bad solder .Too bad these company do not give schematics (Fluke, Keithley etc) anymorehttps://doc.xdevs.com/article/fluke/

author: hitecelec
author_rank: Regular Contributor
timestamp: February 07, 2020, 06:31:04 am
content: thanksAnand

author: Kleinstein
author_rank: Super Contributor
timestamp: February 07, 2020, 08:59:30 am
content: The input protection part with the resistors / MOVs and relay is not that complicated and secret. It should be easy to reverse engineer that small part. The circuit should not be much different from other comparable meters.Not working can also mean different things: more like a short or an open input or to low an input. This would also tell if one more looks for a open joint or a fused MOV or diode.A first point would be to inspect for visible damage like bad solder joints.One could also measure externally it the 10 M input impedance is present in the high volts ranges.Also 4 wire ohms could be worth a test. To me it is more odd that 2 wire Ohms can still work of voltage reading does not.

author: hitecelec
author_rank: Regular Contributor
timestamp: February 14, 2020, 09:54:51 am
content: hellothanks . will try.I would also like to know what is the best method to clean the 8808A front panel keypads.
Fluke 8808A/Tektronix DMM4020 - Troubleshooting the Fleet - Page 1
Forum section: electronics / repair

author: Eiskalt_NX
author_rank: Newbie
timestamp: March 19, 2024, 03:27:13 pm
content: I'm a student technician in my University's electronics shop. ~700 units of test equipment in the labs and in storage. Mainly HP & Co., along with some Tektronix; spans early 90s to about 2019. Current task is working through ten Tektronix DMM 4020 aka Fluke 8805A. I have been unable to find a proper service manual for either of these models. I've read through the user and calibration manuals, plus some online content, but nothing in terms of troubleshooting or schematics so far.I did contact Fluke but they just sent me the calibration manual. Waiting to hear about anything else.The first one I have is unresponsive to power-on. Currently checking the the combined power inlet/fuse holder/input voltage selector assembly and transformer.Others have display issues or are unresponsive to measurements.Main PCB: 8808A-RNET-3001 REV 003 [Date: 1616] [Copyright 2013]Resources I've found so far:https://www.avrfreaks.net/s/topic/a5C3l000000UUWZEA4/t131129https://us.flukecal.com/literature/product-manuals/8808a-calibrationhttps://www.eevblog.com/forum/repair/fluke-8808a-won_t-auto-range/msg838660/#msg838660https://www.eevblog.com/forum/testgear/fluke-8808a-question/https://community.element14.com/products/roadtest/rv/roadtest_reviews/1202/review_of_tektronixhttps://elektrotanya.com/fluke_8808a_calibration_manual.pdf/download.htmlhttps://www.eevblog.com/forum/projects/is-this-capacitor-deformed/msg740503/#msg740503https://www.eevblog.com/forum/blog/eevblog-427-hp-3478a-multimeter-teardown/msg194441/#msg194441Adjacent Information:https://xdevs.com/fix/f8846a/
FLUKE 883A circuit - Page 1
Forum section: electronics / repair

author: Wazza
author_rank: Contributor
timestamp: March 20, 2022, 08:23:51 pm
content: Does anyone have a READABLE circuit/schematic for a Fluke 883A differential voltmeter?The circuit in the milspec manual (the only one I could find) is garbage and is hindering my repair, not helping!

author: lowimpedance
author_rank: Super Contributor
timestamp: March 20, 2022, 11:29:50 pm
content: What about the 887A diff. Voltmeter PDF, does seem to have quite some similarities with the 883A. And the schematic is definitely more readable !.https://assets.fluke.com/manuals/887A_887imeng0200.pdfNot sure if you have seen it but there is also a thread about the 883A :https://www.eevblog.com/forum/repair/fluke-883a-differential-voltmeter-(pics)/Nice old kit, hope you get it going again.
Fluke 8840A - Page 1
Forum section: electronics / repair

author: Maruku
author_rank: Contributor
timestamp: February 18, 2020, 09:02:57 am
content: Hi folks,So I saved one of these from the skip the other day and finally got around to try and fix it. It came back from ETC as faulty and not worth repairing, last calibration was done in 2014 with restricted usage on the 200 and 2000VDC range (non-functional).Took it apart and found the fuse resistor "network" Z302 (P/N: 655852; 9M9 and 100k DC input divider). The 9M9 was open so that will need replacing, for the time being I used a high voltage 10M resistor there. Does Fluke still supply replacement components for these?Also wanted to check the supply voltages whilst trying to fix the unit and the -15V rail is a bit off (table in attachments).Measured the big regulator caps and they seem to be fine, not sure about DCR don't have a meter for that. I also measured ripple on all rails with a AC millivoltmeter and had 4-6mVRMS on all rails.Should I start checking for voltage drops on components using the -15V rail? Tantallum caps possibly?Finally I wanted to test the calibration, so I have pressed the CAL switch, wait for the first cal which is short, press the STORE button and I get an error 42 (Calibration memory write error.)Any experience with that anyone?Cheers.

author: lowimpedance
author_rank: Super Contributor
timestamp: February 18, 2020, 10:43:18 am
content: This model is long obsolete and the only spares available come from other 8840a 's.Why bother with the calibration if the input divider is shot, whatever it was before is now no longer valid anyway.If you manage to find another parts unit you might end up taking bits from this one to fix the other 'parts' unit assuming the input divider is good and cal has not been played with.edit : corrected a typo!.

author: Maruku
author_rank: Contributor
timestamp: February 18, 2020, 02:37:48 pm
content: Thanks for the info, appreciate it.Shame the parts aren't available anymore, its only the 200V and 2000V range that is off anyway.Wonder if the error 42 may be a common fault and someone else has managed to fix that.Cheers.
Fluke 8840A - Codes 7 & 15 - Page 1
Forum section: electronics / repair

author: mbear2k
author_rank: Regular Contributor
timestamp: February 08, 2017, 03:23:58 pm
content: I have a new to me Fluke 8840a and am working my way through cleanup and test. Doing the self-test indicates an error 7 and error 15. These are "1000v DC + 20 Mohm" and ""1000v DC + X10 T/H + 20 Mohm" tests respectively.Error 7 is intermittent in that maybe 3 out of 10 self-tests pass.The manual describes the errors in a general sense, but wanted to see if anyone has experience with these errors and what they found.Thanks

author: mzacharias
author_rank: Frequent Contributor
timestamp: February 08, 2017, 04:32:37 pm
content: On my 8840 A the wires attaching to the Volts - Ohms jacks were creating excess resistance only noticeable in Ohms mode. The push-on connectors were covered in a thin layer of white powdery looking stuff that looked like zinc oxide. I cleaned and tightened the connections - never a problem since. Perhaps dissimilar metals here?

author: mbear2k
author_rank: Regular Contributor
timestamp: February 08, 2017, 04:48:16 pm
content: Good thought. I'll look that over tonight. I'd expect that the self-test with nothing connected would see the jacks wide open. But will look, and maybe see what the F/R switch looks like to start. Then work my way back...I forgot to mention that aside from the errors codes, the high ohms is off. Low ohms seems spot on. I have a precision 10 meg resistor that reads a little over 11 Meg.

author: emartine
author_rank: Contributor
timestamp: October 22, 2024, 12:45:54 pm
content: Hello. You ever got around these errors? I got the same ones.Thank you.
Fluke 8840A repair. Symptom: negative voltages incorrect on the 20V range - Page 1
Forum section: electronics / repair

author: martinr33
author_rank: Frequent Contributor
timestamp: August 03, 2020, 03:37:39 am
content: This unit appeared to be OK everywhere except for the -20V area, where it would cap out at around -6V.All other ranges - positive and negative - were OK.The 20V range has its own buffer amp, with a power supply circuit that tracks the input voltage so as to avoid running out of headroom. This is why the problem only showed up on 20V.The rails with a positive input tracked fine, but with a negative input, the voltage reading was capping out,A scope test showed a very ugly -30V supply.I tracked it down to a 50V 100uF capacitor C611 in the power supply area which, despite no visible signs whatsoever, has no capacitance. Brand is UCC, not a company I associate with this kind of problem. Replacing the cap cured the problem.
Fluke 8840A with a defective front / rear input switch. Advice on repair needed. - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: November 27, 2023, 09:44:50 pm
content: I have a Fluke 8840A that has a broken front / rear input switch. These switches appear to be made up of two 24 pin switches that have been ganged together. The problem with the switch on mine is that the two siwtches have become disconnected from each other. when pushed in and out, the switch closest to the front panel moves back and forth, but the other switch closest to the rear panel will remain in the "rear" position and has to be pushed manually throught the opening at the rear of the switch to reposion it to the "front" position.I have looked everywhere for a replacement switch. Would anyone have a spare switch? Is there a way to reconnect the two switches? should I just forget having rear inputs and just glue the switch to the front position?Other than the switch problem, the meter works very good.

author: alm
author_rank: Super Contributor
timestamp: November 29, 2023, 10:04:15 am
content: I have donor board I could probably desolder the switch from (or dremel out that part of the circuit), but with shipping from EU to Canada (about €12) it may or may not be worth it for you.I would consider disconnecting wires from the rear terminals and soldering jumpers over glueing the switch otherwise since that's more easily reversible.

author: Paceguy
author_rank: Regular Contributor
timestamp: November 29, 2023, 11:22:29 am
content: Yes, I would be interested in the switch that's for sure. Even the doner board minus the transformer if you are interested in parting with it. Thanks for anwering my post!

author: alm
author_rank: Super Contributor
timestamp: November 29, 2023, 01:13:01 pm
content: Okay, send me a DM and we'll take it from there.

author: Paceguy
author_rank: Regular Contributor
timestamp: December 01, 2023, 12:39:53 pm
content: I sent you a PM, thanks!

author: xwarp
author_rank: Frequent Contributor
timestamp: December 01, 2023, 10:12:44 pm
content: If you buy chance need another board for spare parts, I have one or two.

author: Paceguy
author_rank: Regular Contributor
timestamp: December 03, 2023, 01:41:44 pm
content: Hi Xwarp, I sent you a PM.

author: Paceguy
author_rank: Regular Contributor
timestamp: December 29, 2023, 09:48:06 pm
content: A big thanks to ALM! He messaged me and came through with the front to rear switch and a couple other parts I needed from a parted out unit that he had on hand. I received everything today and will get my 8840A's up to scratch.ALM you rock !!!
Fluke 8840A/AF Blank display, 6 right side keys , no response, no relay clicking - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: June 18, 2022, 10:26:44 pm
content: Hi everyone. I have this Fluke 8840A/AF that when powered up has a blank display and the 6 keys on the right side for self test, rate, offset, etc. have no response since I don't hear a relay clicking when they are pressed. When range and function switches are pressed ,relay clicking can be heard. All supply voltages measure within tol and show no ripple when scoped, all power supply caps tested esr OK. Which chips could be the culprit? Oh yes, I reflowed all the transformer pins too. Thanks in advance !

author: bdunham7
author_rank: Super Contributor
timestamp: June 19, 2022, 12:26:49 am
content: None of those six buttons will give you a relay click right away. If you hold the SRQ button down for 2-3 seconds you'll get a click and then a few more clicks over the next 20 seconds or so as it goes through it's self test. The first things to check for no display is whether the VFD filament has voltage and whether the ribbon cables going to the front panel are connected correctly. Do you have the front of the meter disassembled enough so that you can see the VFD tube? The most likely problem by far for no display would be a bad (usually broken) VFD tube.

author: Paceguy
author_rank: Regular Contributor
timestamp: June 19, 2022, 04:58:22 am
content: Even if I hold the SRQ for a few seconds, I don't get the relay clicks from it going into the self test sequence. The VFD tube looks good. All the connections to the display board have been checked and the ones that are soldered were re-soldered. Same with the two filament pins on the power transformer. Could it be U212 ?

author: bdunham7
author_rank: Super Contributor
timestamp: June 19, 2022, 01:07:42 pm
content: You need to do more diagnostics before you can conclude that the processor has failed! Sure, it could be U212 since pretty much everything depends on that, but the fact that you do get responses to other buttons seems to indicate that it is not dead. The display multiplex is also used to scan the keyboard. If you look at the attached picture, on the right side there are the digit selection lines G0-G7 and then the segment lines Pa, Pb.....DP. They both are active high (~30V) and if the digit and segment lines are both high, then that segment should light. You need a scope to look at those lines to see if they are active or not.
Fluke 8840A/AF  Mysterious parts, Need help. - Page 1
Forum section: electronics / repair

author: sampler1
author_rank: Regular Contributor
timestamp: April 10, 2020, 02:24:51 am
content: Hi Folks,I purchased an 8840A/AF. When I turn it on it cycles on and off with the relay clicking. First thing I did was to check the voltage rails and they all seem ok with the exception of the-8.2Volt rail. It reads 5.2volts. I ended up checking everything from the Bridge to the test points in that section and all was good. Two mysterious discoveries were made..R601 is supposed to be 560 ohms and it had a factory installed 1 kilohm resistor? Next I discovered I cannot find anywhere CR617 (8.2v zener)?? I have searched Hi and low and it does not seem to be in the circuit, in fact it is not even listed on the parts location??ANY Ideas?I am also trying to figure where this -8.2 volt rail goes and where it is used.Any help would be appreciated.I have verified all the capacitors, zener diodes, (except CR617), replaced the regulators, resistors in the section of TP603,604,605,606.I realize most was not necessary because the parts were ok.Help Help ( the manual can be found all over the net , it includes schematics)Garry

author: bob91343
author_rank: Super Contributor
timestamp: April 10, 2020, 05:24:12 am
content: I found R602 which is connected to the 'missing' zener.They must have changed the unit somehow.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 10, 2020, 11:59:38 am
content: Maybe some typo errors in the service manual or the pcp prints ??I see some -7 volts on the pca board, figure 9-3 but not in the psu section, surely typo mistakesmanual taken from there:https://www.artisantg.com/info/PDF__466C756B655F38383430415F4D616E75616C.pdfThis artisantg manual is incomplete-------------------------------------------------------On ko4bbthere is an -8.2v going into the pca section a/d pin 17, figure 10-2manual from therehttp://www.ko4bb.com/manuals/45.78.238.75/Fluke_8840A_schematic_sheet2_ADC.pdf-------------------------------------------------------Since the 8842 is similar, check the table 6-22 it tells you where the -8.2v are going, it goes to u303 and u304http://www.ko4bb.com/manuals/45.78.238.75/Fluke_8842A_Digital_multimeter_Service_Manual.pdfIt depend wich schematic source you use loll

author: sampler1
author_rank: Regular Contributor
timestamp: April 11, 2020, 11:42:39 pm
content: I found out the missing Zener is not used and the resistor was changed to 1k.the -8.2v is going to u303 and u304.Figure 10-2 is a hacked copy of the real 8840 manualThanks for the info guys..
Fluke 8840A's with similar problems. - Page 1
Forum section: electronics / repair

author: Paceguy
author_rank: Regular Contributor
timestamp: July 02, 2024, 11:14:51 am
content: I have two Fluke 8840A's with similar problems:1st one: Powers on, display works. Once I go thru the self test, the keypad becomes unresponsive, none of the keys work remains on DC range and measures DC voltages. The self test shows no errors. If I power down and turn it on again, it won't do the self test. If I power it down and wait for a hour or two, I can get it to self test but right after that the keypad becomes unresponsive again.I have tried swapping out U212, issue remains. Could it be U203 or U208? Power supply voltages are all dead on.2nd one: Powers on, display blank, can hear relays click when range and function keys are pushed, the 6 keys on the right side, ( rate, trig, offset, SRQ) appear unresponsive no relay clicking heard when pressed.I switched out U212 and U202. No change. Power supply voltages are good. Could it be U203 or U208?Any advice would be much appreciated. Yes, I have a scope, and Pace desoldering equipment. I have repaired other 8840/8842A's but it's the first time that I run into these problems. Thanks in advance.

author: Slh
author_rank: Regular Contributor
timestamp: July 02, 2024, 11:47:53 am
content: Are the power supply voltages dead on before and after the self test that makes the first one unresponsive? When mine was playing up something in U301/U302 or U303 (can't remember off top of my head but it's in my posts) was latching up when cold and drawing too much current but not when hotnso sometimes the voltages were dead on.

author: J-R
author_rank: Super Contributor
timestamp: July 02, 2024, 05:03:14 pm
content: Quick question: did you already reflow the transformer connections?

author: Paceguy
author_rank: Regular Contributor
timestamp: July 02, 2024, 06:40:32 pm
content: Quote from: J-R on July 02, 2024, 05:03:14 pmYes, reflowed the transformed connections.

author: Paceguy
author_rank: Regular Contributor
timestamp: July 02, 2024, 06:42:08 pm
content: Quote from: Slh on July 02, 2024, 11:47:53 amI will check the voltages in both conditions. Thanks.
[SOLVED] Fluke 8842A DMM - no display - Page 1
Forum section: electronics / repair

author: enut11
author_rank: Super Contributor
timestamp: November 09, 2023, 06:52:54 am
content: My Fluke 8842A DMM has a blank display. I checked all the supply voltages, replaced the electros, re-soldered the transformer PCB traces, checked for any burnt or overheated parts, all to no avail. Also checked the 4.5vAC and 5v DC bias to the display and all good. Finally got around to dismantling the front panel and I found what looks to me like a dead display with two 'smoke' traces at the top - see pic. In the process of dismantling the meter I managed to break the mains power switchSo, now looking for a replacement VFD and they seem to be very scarce. I also have a vague memory of someone who produced a custom LCD drop-in for the 8840/42 but could not find a lead on that one.enut11

author: TheDefpom
author_rank: Frequent Contributor
timestamp: November 09, 2023, 08:00:43 am
content: Have you checked the driver IC's for data in/voltages out? (check on a scope for the pulses)The drivers are U215, U217, U218 they also have a -30V rail just to drive the display, make sure that is present.

author: J-R
author_rank: Super Contributor
timestamp: November 09, 2023, 09:34:01 am
content: https://www.ebay.com/itm/155853129116https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/

author: enut11
author_rank: Super Contributor
timestamp: November 09, 2023, 08:07:58 pm
content: Quote from: TheDefpom on November 09, 2023, 08:00:43 amThe rail at the regulator output measures -5v with the display connected and -30v when I unplug the display.This seems to indicate a dead VFD?

author: floobydust
author_rank: Super Contributor
timestamp: November 09, 2023, 08:20:16 pm
content: To my eyes, the VFD display is dead - it's got air in itTheGetterin the two corners, once it turns white and flakes off inside, is a clear indicator. I would look for cracks or chips on the display that let air in. Healthy Getter is usually black or chrome.If this is true (air in tube) the filaments will keep drawing higher than usual current and not glow orange.

author: enut11
author_rank: Super Contributor
timestamp: November 10, 2023, 06:59:52 pm
content: Quote from: J-R on November 09, 2023, 09:34:01 amThanks everybody for your suggestions.Just bought the Ukrainian LED module, currently the cheapest solution for my problem.

author: enut11
author_rank: Super Contributor
timestamp: December 16, 2023, 07:37:20 pm
content: I received my display kit from@AHOL. 3 weeks earlier than forecast!The only problem was that we were about to go on holidaysBack now and looking forward to getting my 8842 back in service.enut11PS5 stars for customer service

author: enut11
author_rank: Super Contributor
timestamp: December 17, 2023, 07:09:30 am
content: Just finished installing@AHOL's LED display in my Fluke 8842A and it mostly went well. My experience notes in Reply #96 athttps://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/new/#new
Fluke 8842A, Z101 network smooshed up against metal shield - Page 1
Forum section: electronics / repair

author: Jester
author_rank: Frequent Contributor
timestamp: December 23, 2021, 07:05:02 pm
content: Picked up a used 8842A today and noticed the Z101 resistor network is pressed up against the metal adjacent to it, I'm guessing it's not supposed to be touching. The side towards the shield is ceramic so likely not conducting. I'm guessing that the resistor network should be straight up and not touching. I'm tempted to nudge it over gently, I'm not sure how fragile these are?Thoughts

author: Kleinstein
author_rank: Super Contributor
timestamp: December 23, 2021, 09:31:21 pm
content: I don't think the resistor network touching the metal is a problem. Bending the pins can effect the resistors a little - probably more than the effect of touching the metal. In the newer 8858 it look they extra have similar resistors attached to metal.Ceramic is hard, but brittle. So often it can withstand quite some force, but the is a small chance for early failure even from relatively small fore, if there is already a minor crack.

author: bdunham7
author_rank: Super Contributor
timestamp: December 23, 2021, 09:46:05 pm
content: If it is actually touching, you probably are safe gently pushing back a little bit. If not actually touching, I'd leave it be. I avoid disturbing these as much as possible and you must resist the urge to straighten them all out.

author: Jester
author_rank: Frequent Contributor
timestamp: December 23, 2021, 10:01:13 pm
content: Well it does not seems to be effecting the measurement, I fixed the 2nd 8842A I received today and after warming up both, they are measuring the same value to within 1 or 2 counts, usually the exact same count pretty amazing for a 30 year old meter.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 23, 2021, 11:51:12 pm
content: If it still work while physically touching i would not worry, if you move it you can or could create a mecanical stress ... i would not botherAint broke dont touch it ...

author: Jester
author_rank: Frequent Contributor
timestamp: December 24, 2021, 12:38:28 am
content: Quote from: coromonadalix on December 23, 2021, 11:51:12 pmAgreed
Fluke 8845A  8846A Electrolytic Capacitor Replacement    - Page 1
Forum section: electronics / repair

author: gogoman
author_rank: Regular Contributor
timestamp: December 27, 2022, 03:54:02 am
content: Hello all, What brand/series of cap's did you use and would you mind sharing the BOM.thanks gogo

author: Miti
author_rank: Super Contributor
timestamp: December 28, 2022, 12:20:12 am
content: Did you measure them and concluded that they need to be replaced? I remember measuring some in my 8845 and the conclusion was-don’t touch them.

author: gamalot
author_rank: Super Contributor
timestamp: December 28, 2022, 10:35:59 am
content: Yes, why replace them? Inside my Tektronix 4040, the plastic jackets on those electrolytic capacitors shrank a lot, look ugly, but they seemed to work fine.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 28, 2022, 04:45:01 pm
content: Good brand is NichiconI recapped my 3x 34401a meters with them, for the tantalums can't remember, they where way older than theses meters lollBut if the meter work okay there is no rush, you need very good skills and the proper tools ...

author: gogoman
author_rank: Regular Contributor
timestamp: December 29, 2022, 02:27:26 am
content: I would not replace them if I did not need toBOM (to be confirmed)Value Voltage qt Comments15000uF 16 1 TH6800uf 10 1 TH47uf 100 1 TH220uf 50V 2 SMD1000uf 10V 1 SMD2200uf 35V 2 ?Is the voltage rating of the 220uf and 1000uf correct, attached are pic'sthanks

author: Miti
author_rank: Super Contributor
timestamp: December 29, 2022, 03:18:04 am
content: My go to brand/series for recaping instruments is Nichicon PW. I used them in switching power supplies and main boards and they never failed me. I recaped oscilloscopes, lcd monitors, signal generators.
Fluke 8845A DC Voltage and Resistance Measurement Troubleshooting - Page 1
Forum section: electronics / repair

author: ransonjd
author_rank: Contributor
timestamp: March 09, 2020, 08:09:09 pm
content: Just got news from the calibration lab that the Fluke 8845A that I bought is reading out of tolerance in the 10V and 1000V DC ranges, and the 1M, 10M & 100M 2-wire resistance ranges. The resistances are reading low, and the voltages are reading high. Any thoughts on where I should start for troubleshooting?Thanks!

author: Kleinstein
author_rank: Super Contributor
timestamp: March 09, 2020, 09:21:00 pm
content: A first point to check is usually the supplies. Another point to test at a DMM is input current - this could especially effect the higher resistors.I don't think there is a simple common failure to cause a higher voltage reading and a lower resistance value.

author: ransonjd
author_rank: Contributor
timestamp: March 19, 2020, 06:57:50 pm
content: The main supplies all seemed to be okay. However, the negative supply for U37 seems crazy. I tooksome video looking at pin 3 of CR36.Does anyone know how this supply is generated, and what U37 (DG444 analog switch) is doing? I'm trying to slowly trace back the noise to the source, but it's slow going.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 19, 2020, 07:43:21 pm
content: AFAIK there is no available schematics for this DMM. So one would likely need to do some kind of reverse engineering / guessing from the signal what function the chips have. So start with a good photo and maybe text information from the manual / service manual if available.Sometimes one could follow the signal path by applying a low frequency test signal to the input and check a few amplifier outputs. Usually the non AZ mode would be easier for this.Another way to look at it would be to start with a few more readings. So check some +- 1 , 2, 4, 8, 10 V in the 10 V range and a few tests in the 1 / 100 / 1000 V ranges. Another point to check may be the input current: so what is it reading with a 1 or 10 M resistor to ground. Sometimes the exact error symptoms can narrow down the fault. One would than still need to locate the parts on the board.The DG444 is not super low leakage, so I don't think this would be directly switching the input signal. The DG444 may be used to set the amplifier gain or maybe controlling JFET gates. I could also be used to switch an already amplified /buffered signal.The waveform may indicate something like auto zero switching (between the input and zero) - one could check this by comparing AZ on/off mode. Without a plan CR36 does not tell us anything what signal is measured. With the DG444 or OPs one could at least tell if the signal is an output, control signal or supply.The voltage looks somewhat odd, as there is no fixed level. So this could be something like a FET gate signal or similar, or a consequence of a broken part. The signal definitely noise not look healthy. With the higher voltages this looks like oscillation of maybe an open input (this can happen with JFET switches if the gate drive does not follow).
Fluke 8845A No Display - Page 1
Forum section: electronics / repair

author: EddyInChicago
author_rank: Contributor
timestamp: November 08, 2020, 11:36:48 pm
content: Hi All,I recently acquired a Fluke 8845A that has a blank display. Checking some test points I came across one TP that is supposed to give me 60V, but is giving me 2V instead.I am getting about 90V at the bridge rectifier near that TP. For some reason I am not able to upload or attach a picture of the board. I get a message to contact theADMINISTRATOR.All help is appreciated.Thank you,Ed

author: EddyInChicago
author_rank: Contributor
timestamp: November 09, 2020, 12:28:33 am
content: OK.....so I was able to save the photo as .PDF and upload it. Hope this helps.

author: ledtester
author_rank: Super Contributor
timestamp: November 09, 2020, 08:19:07 pm
content: Don't have any info on diagnosing the PCB, but I would try testing out the meter itself using the GPIB / RS232 or Ethernet interface.GPIB and Ethernet connectivity might require configuration you would normally do from the front panel. But you should be able to connect via RS232 using this recipe:- use a null-modem serial cable to your computer- connect using a terminal program set to 9600 baud, 8N1- issue a command like*IDN?followed by CR LF and you should get back a response that begins withFLUKE,8845A,...If you get this far I can guide you through some more commands.Full docs are here:https://xdevs.com/doc/Fluke/8846A/8845a_8846a_programmersmanual.pdf

author: EddyInChicago
author_rank: Contributor
timestamp: November 09, 2020, 10:35:44 pm
content: ledtester,Thank you for that. I will try this and see how far I can get. I've never done this before. So I'll do some research as to how to do thisprocedure. Stay tuned. I'll keep you posted.Thanks,Ed

author: EddyInChicago
author_rank: Contributor
timestamp: November 21, 2020, 12:48:21 am
content: Hi All,So I fixed the no display problem by changing out the two parts listed below:1) NC7SZ14M5X - This is a Schmitt trigger / Inverter2) SQ4532AEY-T1_GE3 - This is a N Channel MOSFETWhen I changed those two components, I got the 60V at the test point. Display working perfectly now.Those are the U6 and Q2, respectively.Thanks,Ed
Fluke 8845A Not holding calibration  - Page 1
Forum section: electronics / repair

author: EddyInChicago
author_rank: Contributor
timestamp: November 13, 2020, 12:12:31 am
content: Hi All,I have a Fluke 8845A that is going out calibration. The following is what I was told by the person that calibrated it and it's history."Hey there Ed.The Fluke 8845A sn: 9407014 has had a history of losing the calibration corrections made on the DC Volts function.2008 our first year to calibrate the item, we received the unit being out (high) by 0.03% on all DC ranges.We would go through the soft calibration and take our outgoing data and we can see the unit has come back into tolerance.The next year we would receive it again and it would now be reading 0.04% high on DV functions only. Again we would go through the soft cal and get great results on our outgoing data.Third cal cycle the DMM showed errors not only in DCV, but all other functions being 0.2 % high.Then it was sent off to Fluke for Repair/Calibration, (Certificate # 2441853-9407014:1309112306)."Has anyone had this problem before (or something similar)?What components can be causing this? (Where should I look)?Any help is appreciated. I also have the calibration data for this DMM. If that helps, I can attach them.Thank you,EdSeems the Firmware did not cure it long term.When I took the data this morning, it nearly mirrored the 2008 data sheet for as far as I got.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 13, 2020, 08:40:18 am
content: I don't know the details of the 8845. A more or less continuous drift of the scale factors would point to an analog problem, not a problem with the digital / software side. In theory a failure of the calibration memory can cause trouble but this would be more like a sudden total failure and is usually caught by some check sums to give an error message.The analog parts they may show drift would be the voltage reference and depending on the details of the DMM also some resistors in the ADC could effect the calibration. Some DMMs do a self check or automatic calibration on the ADC gain factor and other don't. Not sure how the 8845 handles this. For the prime range (e.g. 10 V) there should be no other stage with gain.Other ranges have the input divider or additional resistors for the gain.Besides drift in the resistors it could also be board leakage due to contamination. For the reference there may be an indirect effect from the supplies, though not very likely.One could check the input current / bias current. This is relatively low effort via a high resistor or drift rate with a capacitor at the input. The input bias is not directly related to a gain error, but contamination would likely also effect the bias.Another point may be a visual inspection, e.g. looking for leaking capacitors (this is a known problem with some Keithley meters).Checking for reference drift takes time.