Faulty Fluke 111 - Page 1
Forum section: electronics / general

author: catcow1234
author_rank: Newbie
timestamp: November 04, 2012, 04:53:01 pm
content: Hi all.I've been a fan of Dave's blog and the forum for ages and I thought it was about time to sign upI'm hoping somebody can point me in the right direction to help me fix my Fluke 111 multimeter?When selecting resistance and the meter shows about "-280k" and slowly drops before showing 'OL'. It's like watching a cap discharge on volts. Also the buzzer always sounds on the continuity setting.All other settings are fine.I can't find a service manual or schematic on this meter so i'm hoping someone might be able to help me out.Thanks

author: retiredcaps
author_rank: Super Contributor
timestamp: November 04, 2012, 08:11:31 pm
content: You may have to dismantle it a bit more and check the other side of the pcb. Maybe give the range switch a good cleaning?

author: ModemHead
author_rank: Frequent Contributor
timestamp: November 05, 2012, 01:13:50 am
content: If you take it apart, don't stop with the range switch, clean the whole thing with IPA and blot with a paper towel, allow to dry. The tiniest of leakage currents through film and/or contamination between high-impedance nodes can cause wonky behavior like you describe.Although the beeper malfunction does suggest a more low-impedance fault...Are you sure the diode and capacitance settings are OK? Those functions have a lot of commonality with ohms and continuity.

author: catcow1234
author_rank: Newbie
timestamp: November 05, 2012, 09:14:01 pm
content: Thanks for the advice.I removed the display and gave it a good cleaning with IPA and a clean brush. I also gave the switch a good cleaning but with no luck.I've measured most of the smd resistors which all seem fine and a few of the caps but nothing stands out. All the larger components also check out ok.I tested the meter again after the clean and the Vdc range is working fine, as is the diode test but the capacitance test reports a 47u cap as being between 1700u and 1900u. Also the continunity buzzer now starts at 79R and slowly drops until it hits 60R and the buzzer sounds and the resistance range reports 270R and slowly drops over time.The circuit doesn't really resemble any of the other Fluke models (ext 1.25v REF diode, etc) so I might have to lay this to restThanks again

author: ceecrb1
author_rank: Contributor
timestamp: November 05, 2012, 09:30:45 pm
content: Hate to be the preverbial vulture...... but..if you DO lay it to rest.. and your in europe, I wouldnt mind the plastic casing etc!My work supplied meter is the 111 and its been through a fair few gigs and under staging and through access holes etc etc..

author: retiredcaps
author_rank: Super Contributor
timestamp: November 05, 2012, 10:44:01 pm
content: See my thread and ModemHead's suggestion about the dental pick as a last resort before giving up?https://www.eevblog.com/forum/general-chat/fluke-77-ii-incorrect-readings-on-all-ranges/

author: ModemHead
author_rank: Frequent Contributor
timestamp: November 05, 2012, 11:20:32 pm
content: Didn't suggest the pick this time, the OP's meter looks pretty clean to begin with. Couldn't hurt, though, as long as you're careful.Too bad we can't locate a schematic, very difficult to troubleshoot without one. Just some random thoughts: one of the MOVs is usually dedicated to the ohms sense line, maybe check all of them for leakage. You initially reported the erroneous values were negative. This could be a clue that the fault current is coming from something connected to Vss and not the ground/COM terminal.