Another Fluke87 problem - Page 1
Forum section: electronics / repair

author: planenut2000
author_rank: Contributor
timestamp: September 06, 2021, 01:03:09 am
content: Sorry im new here and if my problem has been discussed before i apologize.My fluke 87 shows a -34Kohms on the ohm scale with no leads. it also shows -4 volts on the dc volt scale, again with no leads.All other positions look normal. I had it sent into a repair facility ( not Fluke Co.) They weren't able to find anything wrong with, but installed a new lead jacks.Any ideas on where to look?

author: retiredcaps
author_rank: Super Contributor
timestamp: September 06, 2021, 01:15:26 am
content: Take it apart and post clear focused pictures of both sides of the pcb.If you're lucky, it could be a simple IPA bath cleaning or it could be your input protection components are bad.Do you have another working meter to make measurements of the input protection components?

author: planenut2000
author_rank: Contributor
timestamp: September 06, 2021, 01:22:32 am
content: Thanks for the replay, i do have another meter a fluke 88, buts its at work at this time. it will be a few days until i can get it.

author: planenut2000
author_rank: Contributor
timestamp: September 06, 2021, 01:34:52 am
content: Here are the pictures

author: planenut2000
author_rank: Contributor
timestamp: September 06, 2021, 01:36:18 am
content: 2nd pic

author: retiredcaps
author_rank: Super Contributor
timestamp: September 06, 2021, 06:24:39 pm
content: While you wait for the Fluke 88, take a look at modemhead's post and check the rotary switch for debris.http://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/http://mrmodemhead.com/blog/fluke-83-dmm-repair/Since you mentioned they installed new lead jacks, this might interest you as well.http://mrmodemhead.com/blog/fluke-80-series-jack-assembly-rebuild/There's a lot of good info on modemhead's site.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 06, 2021, 06:36:13 pm
content: When your 88 arrives, usehttp://bama.edebris.com/download/fluke/87/fluke-83-85-87-multimeters-sm.pdfpages 45 and 46 for your references.Check R1, R2, RT1, E1, RV1 and RV2. Their resistance reading should be as follows.R1 = 1KR2 = 909KRT1 = 1.5KE1 = 0LRV1 = 0LRV2 =0LReport your findings for the above.

author: bdunham7
author_rank: Super Contributor
timestamp: September 06, 2021, 07:12:21 pm
content: In addition, what does it read on DCV with the input shorted? And can you use the other DMM to actually measure the voltage at the 87 input jacks to see if the 4V is actually there and if it changes at all when measured?

author: planenut2000
author_rank: Contributor
timestamp: September 07, 2021, 01:11:58 am
content: i put the 87 back together to check the voltage on the dc scale. when the leads are shorted it drops to zero volts. when the voltage is measured with a cheap 2nd meter, the voltage is pulled down to a little under 3 volts and is displayed on both meters

author: planenut2000
author_rank: Contributor
timestamp: September 07, 2021, 11:22:51 pm
content: R1-reads 882mega ohmsR2-3.4 k ohmsE1- 1.4kohmsRV1-OLRV2-OLNot sure which one is RT1

author: planenut2000
author_rank: Contributor
timestamp: September 07, 2021, 11:36:12 pm
content: If RT1 is yellow and looks like a capacitor with a slot cut in it, then measured from the other side of the board it is open(OL)

author: bdunham7
author_rank: Super Contributor
timestamp: September 08, 2021, 02:38:34 am
content: I think that's it. You can replace it with a 1.5K resistor(or so, anything in the ballpark will work fine) for testing purposes. I'm pretty sure your troubles won't end there, but you have to start somewhere.

author: planenut2000
author_rank: Contributor
timestamp: September 08, 2021, 03:01:20 am
content: looks like the R1 and R2 are also way out of range

author: planenut2000
author_rank: Contributor
timestamp: September 08, 2021, 03:03:44 am
content: and the E1 is out of range also

author: planenut2000
author_rank: Contributor
timestamp: September 08, 2021, 03:16:05 am
content: I think 2 components are misplacedthe E1 and RT1 are in different locations on this meter compared to another pic of a 87 on this site.

author: planenut2000
author_rank: Contributor
timestamp: September 08, 2021, 03:20:41 am
content: Heres the pic of another early Fluke 87

author: bdunham7
author_rank: Super Contributor
timestamp: September 08, 2021, 04:48:45 am
content: Quote from: planenut2000 on September 08, 2021, 03:16:05 amI wouldn't jump to that conclusion--the boards are different revisions and the manual I'm looking at is earlier than your meter. You should follow the traces and see how they are connected--the actual schematic is unlikely to change all that much. If the PTC and GDT are actually misinstalled there must be a story there somehow.Here's the schematic I'm looking at:

author: retiredcaps
author_rank: Super Contributor
timestamp: September 08, 2021, 05:28:35 pm
content: Quote from: planenut2000 on September 07, 2021, 11:22:51 pmReplace R1 with anything close to 1K ohm and retest your meter. If meter works, then we can get a proper rated replacement.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 08, 2021, 05:29:15 pm
content: Quote from: planenut2000 on September 07, 2021, 11:36:12 pmThat's your spark gap and it should be 0L.

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 12:01:33 am
content: I will try to find a 1 kohm resistor locally to try, Thanks for your help!!Theres something im not understanding however. Look at my pic attachment. why is the r2 position a 3.5kohm resistor and the r1 resistor is the 909 kohm

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 12:30:27 am
content: You simply need to either find a manual that matches your revision or just try and work through with what you have. I would start by concentrating on any components that don't measure as marked and worry about the remote possibility that someone has mixed up the parts later. If you measured the components using the board drawing I have, it looks like everything is fine except that the 909K resistor is mostly open--or did you misread your meter and you meant 882kiloohms, not megaohms? In that case, all 4 input components seem fine, or at least good enough not to cause your issue.And are you sure yours is an original 87 and not an 87-3?

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 12:59:50 am
content: I doubled checked the R1 reading and its mega ohms. I purchased it used from an ebay seller, and he said he repaired it. It never seemed correct in the readings. Im used to my trusted fluke 88, all the readings on that are pretty stable. So after putting up with the flakey readings for a while i sent to a business in either S. carolina or N carolina that advertises fluke meter repair. They said they found nothing wrong but replaced the input jacks just because they fail sometimes. When i got it back from them it didnt seem much better. But my wallet was $150 lighter. After i ignored the fluke for several months i tried using it and found the problems im trying to fix now.Im an auto mechanic and aircraft mechanic and i dont like to give up on things until i get to the root cause of the issue.

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 01:10:36 am
content: just 87

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 01:13:47 am
content: These look more like a match with your -AC revision?

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 01:22:38 am
content: Thank You very much, that exactly what i have. So my R2 is out of spec.

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 01:25:20 am
content: So there was another long thread on Fluke 87 repair featuring usersManulandMultiple Cheese Slices, you should find and read it. The way the power supply is set up, the battery negative isbelowVss. I'm not sure how it all shakes out internally, but the fact that the indicated negative voltage was actually present on the terminals when you checked seems to indicate that somehow negative battery voltage is leaking back into the input somewhere. One thing to try would be to put the meter in the ACV position (battery installed) and then measure with another meter with the black lead going to the com jack and the other lead to terminals 3 and 4 (one at a time!) of the front switch--if that's feasible. If your negative voltage shows up there, then you have a better idea where it might be coming from.

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 01:26:53 am
content: Quote from: planenut2000 on September 09, 2021, 01:22:38 amAre you sure? What sort of meter do you have that measures 882 megohms??

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 01:29:37 am
content: fluke 88

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 01:36:16 am
content: crap, i missed the decimal point. it was .896mega ohms. so the R2 is good

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 02:13:04 am
content: Quote from: bdunham7 on September 09, 2021, 01:25:20 amI dont see a way to do the test you suggested

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 02:23:04 am
content: With the meter disassembled and just the board laying on the bench? Just make sure you know which position is ACV, and don't worry about the display not being installed.

author: planenut2000
author_rank: Contributor
timestamp: September 09, 2021, 10:54:50 am
content: i put in both the ac volt scale and checked all the taps on the selector switch, nothing near the -4 volt. also did the same thing in the dc volt scale same result

author: Manul
author_rank: Super Contributor
timestamp: September 09, 2021, 05:57:48 pm
content: Quote from: planenut2000 on September 07, 2021, 11:22:51 pmMaybe it was 0.882M? What kind of meter you used to measure it 882M? Does that meter really go up to GigaOhm?So as I understood, there is current injection happening somewhere. 4 volts is "real" volts. The fact that it goes zero after shorting probes and that it drops to 3V under load of 10M (?) may suggest the likely point of injection.Edit: I just saw that megaohms question is already cleared. Nevermind.

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 06:42:27 pm
content: Quote from: planenut2000 on September 09, 2021, 10:54:50 amOK, so under those conditions (in DCV) are you still seeing the voltage at the input jacks, but not at terminal 3 or 4 of the front selector switch?

author: bdunham7
author_rank: Super Contributor
timestamp: September 09, 2021, 07:56:26 pm
content: Another thought that might be an easy fix--is is possible there is some board contamination or a dead spider or whatever right in the area where the battery clip attaches to the board and the input jack is? Perhaps under the input jack assembly? You could try some IPA and then blowing it out with compressed air to see if that makes any difference.

author: planenut2000
author_rank: Contributor
timestamp: September 10, 2021, 01:27:57 am
content: I do see what looks like a very crappy solder job on the volt ohm tap of the input jacks, i will re-solder it tomorrow

author: planenut2000
author_rank: Contributor
timestamp: September 11, 2021, 03:22:18 am
content: well re-soldering the cold joints on the input jacks and i re-soldered the 9 volt battery to to circuit board connections didnt help. now i have warning beeps of having leads in wrong positions

author: bdunham7
author_rank: Super Contributor
timestamp: September 11, 2021, 03:54:25 am
content: If it was me, I'd take the input jack assembly off and have a look. I realize that you had the problem before they replaced that, but I'm having trouble imagining that this issue is likely to be anywhere else. I don't know how difficult getting that off would be for you, but if you have desoldering ability, I'd try that.

author: planenut2000
author_rank: Contributor
timestamp: September 11, 2021, 04:10:37 am
content: i agree, i was thinking about doing that. Are there any good quality input jacks on the market for this model. I installed the jacks previously on my fluke 88 before.

author: bdunham7
author_rank: Super Contributor
timestamp: September 11, 2021, 04:27:05 am
content: Fluke p/n 826214. eBay seller 'Fluke-USA' hasn't sold me any bad or fake parts yet. Apparently this part is discontinued from Fluke but surplus ones remain in the market plus there are fakes.

author: planenut2000
author_rank: Contributor
timestamp: September 12, 2021, 01:32:37 am
content: Only this i see is the volt/ohm printed circuit is torn, might have happened in the removal

author: planenut2000
author_rank: Contributor
timestamp: September 12, 2021, 01:34:48 am
content: a lot of solder to remove with a radio shack solder sucker

author: bdunham7
author_rank: Super Contributor
timestamp: September 12, 2021, 02:52:54 am
content: Well, now you can power it up and see if you still have the negative voltage at the input jack. I like test equipment, but sometimes I find problems by prodding things with an insulated stick. This may be what happens here! I would look closely at the area where the two green battery wires go around the input area. Is there some gunk or corrosion there? Is it possible that the insulation is cracked on those wires or they have residue from previous battery leakage?

author: james_s
author_rank: Super Contributor
timestamp: September 12, 2021, 03:19:48 am
content: I cringe at the thought of somebody working on a high end meter with a Radio Shack solder sucker. That's a good way to mangle the PCB beyond repair. I lived with one of those sucker bulb irons for many years before I finally got a vacuum desoldering tool, would never go back.

author: planenut2000
author_rank: Contributor
timestamp: September 12, 2021, 09:26:06 pm
content: Quote from: james_s on September 12, 2021, 03:19:48 amThanks for the help!

author: planenut2000
author_rank: Contributor
timestamp: September 12, 2021, 10:56:18 pm
content: I think i made some progress on the 87. With the input jacks removed i still had the same readings. I did notice that the 2 green wires from the 9 volt battery area looking a little fuzzy, so i re-soldered them.That made a big difference on the readings. now the ACvolts with settle at 11milli volts, dc volts show -1.1 volt, dc milli volt will show -OL ohm scale is toggling into OL and the top of its auto ranging.

author: planenut2000
author_rank: Contributor
timestamp: September 12, 2021, 11:27:40 pm
content: i soldered the input jacks back in. I re- soldered the R1 and R2 and RT1 and E1. now ma AC settles at about 3.2 milli volt. the DCV is showing -.495 volt and is OL or sometimes shows 495milli volts. the Ohmsscale is 3.15 mega ohms.Sometimes when i first switch onto ACV the meter will sound alarm like the leads are in the wrong position until i turn the dial selector back and forth. Do you think at this point it just needs cleaning?

author: bdunham7
author_rank: Super Contributor
timestamp: September 13, 2021, 12:30:41 am
content: It looks like you're in the area. Perhaps an IPA bath and a bit of scrubbing?

author: BMK
author_rank: Regular Contributor
timestamp: September 13, 2021, 12:55:05 am
content: Can confirm I had this exact issue. Weird readings after a sight slight battery leak(Caught early, before any corrosion visible). IPA did not work to clean, eventually used electrolube safewash and another 1-2 washes with IPA and a bake off at 90'C for a couple of hours. Always stuck with me as a lesson in how tiny leakage currents can appear with contamination.

author: james_s
author_rank: Super Contributor
timestamp: September 13, 2021, 02:14:02 am
content: About 30 years ago I built a Heathkit DMM, it was roughly equivalent to the meters you can now get for free at Harbor Freight, maybe a tad better but it was expensive at the time. I still remember the manual was very clear about keeping the PCBs clean and avoiding even fingerprints, and had a procedure for cleaning them.

author: planenut2000
author_rank: Contributor
timestamp: September 14, 2021, 12:38:52 am
content: I cleaned the circuit board twice with Mac's Electronic cleaner from napa auto parts, with a little light tooth brush action. And when my wife wasn't looking i put in her oven at 175 for about 45mins. i would have heated for longer but she caught me!!! But that fixed it. All readings are normal now!Thanks to all you guys for the help!!!

author: james_s
author_rank: Super Contributor
timestamp: September 14, 2021, 03:47:00 am
content: Glad to hear this worked out. It should give you many years of service now that it works.

author: planenut2000
author_rank: Contributor
timestamp: September 15, 2021, 09:16:40 pm
content: Well almost fixed. I'm getting beeping like the leads are in the wrong position, but leads aren't plugged in. This happens when the meter is first turned or when its in a cooler building and usually clears by itself.Anything come to mind that could be temp related?Are the stray mv readings on the ac and dc ok?Otherwise when i use it to measure something it always seems to be working.

author: bdunham7
author_rank: Super Contributor
timestamp: September 15, 2021, 09:40:22 pm
content: The input jacks are all split and the two halves are connected by the lead when you plug it in. The COM and VOLT/OHM jack are tied together but the two current jacks remain split between a lead sensing circuit and the current circuit. Any contamination that allows leakage from one side of the jack to the other will cause this problem. It could be caused by more contamination on the board right near the current jacks or it could be problem inside the input jack assembly itself. For the jacks, I would try pouring in some IPA or your board cleaner, swishing it around, emptying it out and then blowing out with compressed air.

author: james_s
author_rank: Super Contributor
timestamp: September 15, 2021, 09:50:52 pm
content: Maybe try cleaning the jack out with a Q-tip dipped in alcohol? Looks about the right size.

author: planenut2000
author_rank: Contributor
timestamp: September 17, 2021, 03:29:38 am
content: I made some head way again. I re-soldered the input jack block again, re-soldered RT1 and R1, actually bridged them together, they were only a mm apart anyways. re-soldered R7, also W1 and W2. Re-soldered the 9volt battery wires. Cleaned the PCB with electronic cleaner and put it in the oven for 20min at 180. So far the meter shows only 2.8mv on the ac scale, 0 volts on the dcv scale, .2mv on the dcmv scale, OL on the ohm scale.Hopefully i don't get the lead beeping alarm tomorrow when i retry it.

author: planenut2000
author_rank: Contributor
timestamp: September 18, 2021, 03:04:29 am
content: i think i am going to say the meter is fixed. i had it in the refrigerator overnight and all readings were normal with no stray voltages on the dcv or dcmv ranges and less then 1.5 mv on the ac scale. Ohm scale showed OLThanks to everyone who guided this repair!

author: james_s
author_rank: Super Contributor
timestamp: September 18, 2021, 05:14:43 am
content: Certainly sounds like it's working properly. Glad it all worked out.

author: planenut2000
author_rank: Contributor
timestamp: October 17, 2021, 12:19:36 am
content: Well I just give up!!!!I had this meter working great, none of the problems that were talked about earlier. I put it away on the shelf and when i went to use it a couple of days ago its beeping on every setting! i blew compressed air in the input jacks and made no difference.

author: planenut2000
author_rank: Contributor
timestamp: November 15, 2021, 02:41:11 am
content: Very interesting update to this repair!The fluke 87 is working perfectly now!! I did nothing to it except remove it for a few days from a protective foam lined hard case i purchased for it.Is it possible that a sealed case could be holding high moisture or fumes from its mfg process that could be causing the fluke to show stray voltages and beep like the leads are in wrong?Could this be because the prior PCB repairs need to be resealed?If i leave it out of the case everything is normal, If i put it back in the case, the fluke messed up within a few days!

author: m3vuv
author_rank: Super Contributor
timestamp: November 15, 2021, 05:59:03 am
content: I once had an issue with my fluke 83v saying probes were in wrong and beeping,drove me nuts,i first tried cleaning the jacks with cotton buds but didnt help,in the end i unsoldered the jack assy,put it inside a sock and threw it in the washing machine when i did a wash,gave it 2 days in the airing cupboard to dry then refitted it,its been perfect ever since,that must of been 4yrs ago.

author: m3vuv
author_rank: Super Contributor
timestamp: November 15, 2021, 06:06:31 am
content: why tf,do ppl say use ipa to clean corrosion,since when has alcohol dissolved corrosion?,i think you would do better pissing on it imho.

author: Swake
author_rank: Frequent Contributor
timestamp: November 18, 2021, 08:27:37 pm
content: My 30-years old Fluke 85 has the same 'beeping' behavior when it is located in a high humidity environment for too long. Typically this would happen when it is stored overnight in an unheated shed, especially during the winter period. I believe it is due to condensation.I never store it in the shed anymore in the winter months and have not had the beeping error since. Didn't change or clean anything.

author: planenut2000
author_rank: Contributor
timestamp: November 19, 2021, 02:24:26 am
content: My fluke is doing good for now. Its in a cold aircraft hanger and working. It does mess up if it rains for a few days. Right now the humdity is low due to lower temps and snow in the forecast.There should be something to seal the pcb that i repaired previously