FLUKE 25 - Page 1
Forum section: electronics / repair

author: cinis
author_rank: Newbie
timestamp: November 02, 2015, 10:52:44 am
content: Can someone help me with such a problem? Here is link->http://failiem.lv/g/xilesrf#aa/20151102_121346.mp4

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 02, 2015, 11:03:38 am
content: Welcome to the forum! Can you post pictures of the inside of the meter?(for anyone who doesn't want to watch the video, basically the ohms range is continually counting down and the DCV range is counting up)Service manual:http://assets.fluke.com/manuals/25_27___smeng0000.pdf

author: cinis
author_rank: Newbie
timestamp: November 02, 2015, 11:07:24 am
content: Here link to pictures ->http://www.failiem.lv/u/errhbcq#

author: retiredcaps
author_rank: Super Contributor
timestamp: November 02, 2015, 06:07:54 pm
content: The 34 second video shows the ohms range starting at 0L and then counting down to 0.02. The VDC range shows it starting at 0L and then 17.xx and counting up to 19.xx.One thing that hasn't been pointed out yet is that when the meter is switched to VDC, it shows the M ohms annunciator. When the meter is switched to the ohms, it shows no annunciators.Whoever took apart the meter and re-assembled it put the switch in the wrong way (180 degrees turned around)? I would have to search to see how the old 27 is assembled.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 02, 2015, 06:18:46 pm
content: If you watch Dave's eevblog #372 (Fluke 27 review and teardown), you can see at 10:49 when he is testing the VDC accuracy, there are no annunciators showing when it is showing the VDC reading.You can clearly see the ohm annunciators (unit and omega symbol) at 10:14 when he is measuring this resistance standard.So I would say your rotary switch is turned around 180 degrees.While you have the meter open, you can also test all the input protection like the MOVs and PTC "in circuit".The PTC should measure around 1.1k ohm (RT1) and the 5 MOVs (RV1-RV5) should read open circuit resistance (ohms mode).

author: cinis
author_rank: Newbie
timestamp: November 02, 2015, 06:42:20 pm
content: The switch was in wrong direction. Tested these components they are ok. Changed the switch, now the VDC seems to be allright but the ohms- when i turn to ohms they are on 30M, when i put the leads together it is falling till 14ohms, when i release the leads than i have OL. But every time i turn to ohms i have 30M ohms.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 02, 2015, 07:05:25 pm
content: Quote from: cinis on November 02, 2015, 06:42:20 pmSince the Fluke 25 is a 3200 count meter, at 30M ohm, it is pretty close to showing 0L.If all the input protection tests okay, then I suggest you clean the pcb with IPA and let it dry thoroughly.Since the Fluke 25 is o-ring sealed, it should have been super clean inside. If the switch was inserted incorrectly, that implies that someone opened up the meter and potentially contaminated the board with oily finger prints, dust, dirt and debris.See modemhead's method for "dunking" a meter in IPA.https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg633201/#msg633201I do the same and let it dry thoroughly before reassembly. A simple PC fan will help it dry faster.PS. Make sure you are using a new battery for these tests. The Fluke 25/27 will run up to 1000 hours on a 9V battery, but a weak battery may cause funny readings, especially with a contaminated pcb, even though the low battery annunciator is not on.

author: cinis
author_rank: Newbie
timestamp: November 02, 2015, 07:08:54 pm
content: Thank you for all information! Will do that tomarrow. One question- can i do the cleaning in ultrasonic bath with ipa?

author: retiredcaps
author_rank: Super Contributor
timestamp: November 02, 2015, 07:25:51 pm
content: Quote from: cinis on November 02, 2015, 07:08:54 pmSee this recent repair ...https://www.eevblog.com/forum/testgear/fluke-187-reads-2-ohms-high/