Fluke 87 III misbehaves - Page 1
Forum section: electronics / repair

author: jokinpaha
author_rank: Newbie
timestamp: June 20, 2015, 10:14:24 am
content: Hi allI bought a Fluke 87 III off of Ebay just to find out that it doesn't work properly.It first seem to work fine but when I laid it on the table (not so gently) it turned off. I repeated this and it seems to turn off, goes haywire or just freezes.Now I noticed that by turning it on sometimes it beebs, turns backlight on and so on. Sometimes it works just fine but I'm having hard time to trust it.I have taken it apart and inside it seems to be in good condition. I cleaned rotary switch and push button contacts without any progress.Any ideas where to start looking for the fault?

author: tautech
author_rank: Super Contributor
timestamp: June 20, 2015, 11:04:23 am
content: Welcome to the forum.May it have been dropped do you think?First thoughts would be to check PCB and solder joints for cracks, magnification will be handy.Make sure battery connectors are clean and tight too.Sometimes flexing the PCB will make a tell tale click if something is cracked.retiredcapsis our Fluke expert, he might have other suggestions.....

author: retiredcaps
author_rank: Super Contributor
timestamp: June 20, 2015, 03:28:39 pm
content: In addition to the above wrt to battery connector,- check that you have a new fresh battery since a marginal battery can exhibit strange symptoms on the 87 without the low battery icon coming on- check the battery connector to the pcb doesn't have any solder cracks or is coming loose (I have seen that once on a 787), see modemhead's picture below as referencehttp://mrmodemhead.com/blog/wp-content/gallery/8xsw/8xsw_015.JPG- when you cleaned the rotary switch, did you clean both sides as per modemhead's bloghttp://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/- a clear focused picture of your board will help us see if anything is obviously wrong- if all else fails, contact seller for refund (if you don't mind, please post the link to the original auction so we can see what the description says).PS. Everything I know about Fluke meters comes from reading modemhead's repair blog and Excavatoree buying guidehttp://www.ebay.com/gds/Fluke-Meters-Models-and-Series-main-/10000000007478323/g.html

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: June 21, 2015, 01:48:15 am
content: I'll open up my 87III and take the inner shield off to take some pics so there's some reference to compare against. Mine was previously owned by an engineering company that built spacecraft and aircraft systems, so I'm fairly certain it's been properly maintained. Only thing I've ever done to it is change the fuses and adjust it.

author: ModemHead
author_rank: Frequent Contributor
timestamp: June 21, 2015, 02:03:31 pm
content: Quote from: jokinpaha on June 20, 2015, 10:14:24 amThe contacts on the back side are the ones that control power, function selection, and provide a reset between each function, so that's a place to start. The 83-III blog entry linked by retiredcaps above may be useful.

author: jokinpaha
author_rank: Newbie
timestamp: July 05, 2015, 10:57:35 am
content: Sorry about my absence. I have been busy working and whatnot.So a little update on this matter: I went for the obvious first and got a new battery. That didn't make a difference.I'll try to find time to work more on this because all I got right now is chinese credit card sized DMM

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: July 05, 2015, 05:18:13 pm
content: sorry it took me so long to get these pics up for you.... I got a bit sidetracked and forgot. Let me know if you need any more specific ones or any other info.I had a hard time getting good lighting on it for the pics.

author: Electroplated
author_rank: Regular Contributor
timestamp: July 07, 2015, 04:59:15 pm
content: Quote from: Addicted2AnalogTek on July 05, 2015, 05:18:13 pmI dont have that model but looking at the images there looks to be something thatlooks like a cracked capacitor (?) Ive marked in red near the input protection.

author: DmitryL
author_rank: Regular Contributor
timestamp: July 07, 2015, 05:28:21 pm
content: Quote from: Electroplated on July 07, 2015, 04:59:15 pmIt's a spark gap. Deliberately sawn

author: Electroplated
author_rank: Regular Contributor
timestamp: July 07, 2015, 05:44:50 pm
content: Quote from: DmitryL on July 07, 2015, 05:28:21 pmWell ya live and learn, never seen a DSSP before < Slaps own head >

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: July 07, 2015, 09:49:15 pm
content: what do you mean you don't have that model? It's an 87 III. Are there different variations of the 87 III??

author: Electroplated
author_rank: Regular Contributor
timestamp: July 08, 2015, 07:30:05 am
content: Quote from: Addicted2AnalogTek on July 07, 2015, 09:49:15 pmYou do know fluke has a wider range of meters than the 87 III ? As I said, I don't own that model, I DO have the Fluke 87 V, that is a '87' but is different from this '87' because............. its a V not a III :-)--

author: TheSteve
author_rank: Unknown
timestamp: July 08, 2015, 07:11:05 pm
content: The two glass through-hole diodes look rather sloppy bent over. I assume they aren't touching the smt caps below, either way though they don't inspire confidence.

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: July 09, 2015, 01:05:36 pm
content: Yes I know that fluke makes a very wide range of models, and that there are a few in the "87" series, but the title of this thread is " Fluke 87 III ", so I was under the belief that whoever was looking for assistance with their 87 III had the same model as I. That's all

author: Addicted2AnalogTek
author_rank: Frequent Contributor
timestamp: July 09, 2015, 01:07:32 pm
content: Quote from: TheSteve on July 08, 2015, 07:11:05 pmIt's just the angle of the pictures that makes them look like they are bent over laying on the SMT caps, but they are nearly vertical.

author: tooki
author_rank: Super Contributor
timestamp: August 06, 2015, 12:07:37 am
content: Quote from: Addicted2AnalogTek on July 09, 2015, 01:05:36 pm

author: MatthewEveritt
author_rank: Unknown
timestamp: August 06, 2015, 10:45:58 am
content: Just to be clear, because there seems to be some confusion, the images so far have been of a good unitfor reference.We're still waiting to see/hear anything about the faulty meter.

author: cowboy
author_rank: Newbie
timestamp: October 17, 2016, 12:09:01 am
content: thanks to the pics fromAddicted2AnalogTekand help fromretiredcapsI was able to order the burned diode and rectifier bridge in my 87-III

author: jokinpaha
author_rank: Newbie
timestamp: July 08, 2018, 08:05:25 pm
content: [Three years later]I just reassembled the meter that has been on the healing bench all this time and I haven't been able to reproduce the fault, atleast so far. Might have been as simple as the casing screws weren't tight enough so mode selector could disengage when bumped? Who knows?

author: Johnny10
author_rank: Frequent Contributor
timestamp: July 12, 2018, 10:38:11 am
content: I have a couple of these meters I bought from Pawn shops for $50 each.First one had wonky behavior caused by battery cable. Second from cracked solder joint on input.And dirt under main selector switch.They are very rugged units.I use them daily... wish they had better capacitor checking like the 87V. But for the money!!Glad yours is working again.

author: andyrew
author_rank: Newbie
timestamp: January 02, 2020, 10:35:51 pm
content: I've got the same issue with an old 87. I had just cleaned the screen contacts to fix some ghosting and it was working fine afterwards. I sat it down for a couple days and when i went to use it again it was doing the rebooting thing. It wasn't dropped, was working during last use... it just started doing this.Do we still think this might be a pcb issue with a cold solder joint or something cracked? i did a quick once-over and didn't see anything but I'll have to get the magnifier out to do a good look. anywhere I should start looking?

author: retiredcaps
author_rank: Super Contributor
timestamp: January 03, 2020, 06:08:25 am
content: Quote from: andyrew on January 02, 2020, 10:35:51 pmYou can help us help you by answering the same questions in post #3. In addition, is this a Fluke 87 III?

author: andyrew
author_rank: Newbie
timestamp: March 14, 2020, 09:54:23 pm
content: I have again taken apart the rotary switch and cleaned the contacts on the board and on the switch - both sides. i bent the contacts just a little to make sure they were making good, solid contact. i but in a new battery, then replaced the battery connector and made sure the solder joint was good and solid. still the same issue.The front just says fluke 87, no version as you can see in the pics.Please let me know if the pics aren't clear or close enough.Andy

author: retiredcaps
author_rank: Super Contributor
timestamp: March 14, 2020, 10:23:17 pm
content: You have an original Fluke 87 I.I suggest you download the service manual fromhttp://bama.edebris.com/download/fluke/87/fluke-83-85-87-multimeters-sm.pdfand look athttp://mrmodemhead.com/blog/fluke-83-dmm-repair/I suggest you concentrate on section 3-34 of the service manual and check the voltages in table 3-14.Table 3-13 lists the components of the power supply. You should inspect all these components visually to make sure solder contact is solid. The values are all listed for those components in the bill of materials and you can check to see if they meet those specs.Report your voltage measurements for table 3-14.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 14, 2020, 10:34:21 pm
content: It would also help if you had a variable DC power supply to see how much current the 87 is drawing during bootup as well. Or put another multimeter in series with the battery connector to see how much it's drawing.

author: andyrew
author_rank: Newbie
timestamp: March 17, 2020, 08:52:59 pm
content: i dont have a variable ps at the moment so i just hooked up the 9v battery and tried to take a couple measurements. i'm getting 6.6v across vdd and vss and about 3.2 across each of them independently. i'm also seeing a current draw of about .2mA with no screen.do you have a map of where i can check the voltages in fig 3-14? i can find the points on the schematic but i cant translate into physical locations (they're too smalldo the TPs match up to the voltages listed somewhere?

author: andyrew
author_rank: Newbie
timestamp: March 18, 2020, 08:15:15 pm
content: i asked the people at fluke what the problem with this might be and they told me their technicians are telling them that this is a fatal error. they think the problem lies within the processor. if that's the case the only way to fix it would be the replace the processor and i'm pretty sure they don't make them anymoreIf anyone has other ideas please let me know as i'll be very sorry to trash this meter

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 18, 2020, 08:34:36 pm
content: Fluke could be right but you're the one who can actually do the most testing.If you're sure of the switch contacts, battery connection and wires, my next suspects would be the tantalum drop capacitors. It could also be worth the trouble of reflowing the ASIC.

author: andyrew
author_rank: Newbie
timestamp: March 18, 2020, 08:38:32 pm
content: i assume to test the capacitors i need to remove them from the board?and i assume by ASIC you mean the main processor?

author: shakalnokturn
author_rank: Super Contributor
timestamp: March 18, 2020, 10:17:19 pm
content: Quote from: andyrew on March 18, 2020, 08:38:32 pmTantalum drops sometimes show "intermittent" behaviour so this is one of the rare cases where in doubt I just replace them. (I test them out of circuit on the oscilloscope's component tester, I'm not sure how/if the intermittent failure shows on other testers though.)Yes, that's what I meant by ASIC.