I have a broken Fluke 87(I), could it be fixed? - Page 1
Forum section: electronics / testgear

author: adsgrwarg
author_rank: Newbie
timestamp: May 03, 2017, 04:06:43 pm
content: I procured a Series I Fluke 87 DMM a while ago. The meter is broken with no signs of damage on the board. The meter does not turn on nor is there anything on the screen. Only thing it does is make a small sound from the piezo when the switch is turned from AC to DC and vice versa.I have taken the meter apart, cleaned all the contacts inside, checked both fuses and checked that the board and screen get power.The small header for the screen shows 3.3v when the screen is disconnected, but there is nothing on the screen.I haven't found any schematics for this meter, they would be most helpful. I suspect the chipset might be dead, which makes the meter dead too with no hope of recovery unless I find another Fluke 87 with a working chipset.UPDATE: the meter has started to whine! It makes this weird low frequency whine from the buzzer (kinda like a mosquito but lower) when it is turned to off and AC, the whine stops when the meter is turned to DCVideo of the poor meter whining:

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: May 03, 2017, 05:05:13 pm
content: You can find service manuals over at the Fluke sitearchive.Ifthisis the right one, I don’t know.Good luck!

author: retiredcaps
author_rank: Super Contributor
timestamp: May 03, 2017, 10:26:52 pm
content: Look at the service manual and check all the TP (test points). You may have a dead main IC chip. I have a similar problem with a Fluke 87 I and mine is definitely a bad main IC.

author: Electro Detective
author_rank: Super Contributor
timestamp: May 04, 2017, 12:00:54 am
content: Check the rotary selector tracks too, from memory I think mine had some weird carbon looking stuff there, not gold traces.Maybe there is some something amiss, a small bit acting as a bridge or stuck or bad contact/s ?My 20 year 87-1 easily keeps up with todays high end meter specs and worth fixing if cheap to do so.Lots of 87 owners at EEV that can tell you more, good luck

author: retiredcaps
author_rank: Super Contributor
timestamp: May 04, 2017, 01:39:59 am
content: Quote from: Electro Detective on May 04, 2017, 12:00:54 amModemhead has an entry on the above.http://mrmodemhead.com/blog/fluke-83-dmm-repair/http://mrmodemhead.com/blog/fluke-83-dmm-repair/

author: Electro Detective
author_rank: Super Contributor
timestamp: May 04, 2017, 08:59:30 am
content: Quote from: retiredcaps on May 04, 2017, 01:39:59 amOh yeah, definitely check that selector switch and the track for crap, but take it real easy to avoid trashing it

author: adsgrwarg
author_rank: Newbie
timestamp: May 04, 2017, 09:51:33 am
content: Quote from: retiredcaps on May 03, 2017, 10:26:52 pmI tested the voltage reference and pin 6 on U4 (the main IC), and the voltage was incorrect. Definitely seems like the IC is dead. Thanks for the tip anyway.

author: P90
author_rank: Frequent Contributor
timestamp: May 04, 2017, 10:50:26 am
content: Someone must have zapped that meter with a BBQ spark igniter...

author: ModemHead
author_rank: Frequent Contributor
timestamp: May 04, 2017, 05:43:10 pm
content: Quote from: adsgrwarg on May 04, 2017, 09:51:33 amI assume you're referring to the power supply trouble-shooting procedure in section 3-35 of the service manual. In order to confidently indict U4, all previous steps of the procedure must also be performed. This starts in section 3-34, and includes driving the rails with an external power supply. Otherwise there are a number of parts external to U4 that are also responsible for the power supply.Inthis blog post, I went though this procedure step-by-step on a model 83. You may find it useful. In the end, my problem was ultra-simple, but I didn't know it at the time.

author: Electro Detective
author_rank: Super Contributor
timestamp: May 04, 2017, 11:26:23 pm
content: Quote from: P90 on May 04, 2017, 10:50:26 amThere's a guy on Youtube who does that all the time, but I never see him cooking anythingOh well, if he gets hungry enough he may sell some meters to buy a working BBQ

author: snoopy
author_rank: Frequent Contributor
timestamp: May 11, 2017, 12:51:26 am
content: Quote from: Electro Detective on May 04, 2017, 12:00:54 amThanks for this advice. I was able to fix a Fluke 87 that had been sitting around for ages. When you switched it on the display would go hay-wire and the beeper would beep all of the time. So I removed the contact plate and cleaned the carbon tracks with a cotton wool bud and some contact cleaner as well as re-tension the contacts and it is as good as new !! However the connection system between the LCD and PCB is a bit ordinary IMOcheers

author: Electro Detective
author_rank: Super Contributor
timestamp: May 14, 2017, 03:06:03 am
content: Quote from: snoopy on May 11, 2017, 12:51:26 amGood newsand the display issue should be an easy fix too, but beware which method you choose, there are some duds out thereThere may/should be some posts here about it,or go youtube, even Fluke has one too.