Fluke 1507 Insulation Tester - Page 1
Forum section: electronics / repair

author: softwarejedimaster
author_rank: Contributor
timestamp: July 02, 2016, 10:10:05 pm
content: I recently acquired this Fluke 1507 insulation tester and all seems fine except one small issue. It cannot power off. Strange thing when turn the rotary to the off position it still reads volts in the display - the next to last selection before the off position. I thought of checking all the rotary contacts to see if the rotary switch was perhaps installed incorrectly. I found nothing. This meter is pretty new and has no signs of contact wear at all. All else seems pristine. I cannot find any schematic but I downloaded the operators and cal manual and found that it has an auto power off function - typical of these Fluke meters. If I let the default 10 minutes expire the meter does, in fact, power off, but then as the manual suggests, any change in the rotary switch or any button press will take it out of sleep mode and once again turn on. This is not the case. It does not turn on despite any/all button presses or rotary switch position change. In fact, it will only power on if I take the batteries out for a period of about 30 seconds, then reinstall and it comes alive again.I'm wondering if anyone has seen this type of behavior in these fluke meters and can lend me an idea to start troubleshooting. If I had to guess, I would say it has a faulty watchdog device preventing it from going into or out of this sleep mode/ power off mode.Thanks in advance for any suggestions and comments.

author: dohyun
author_rank: Contributor
timestamp: July 03, 2016, 02:40:31 pm
content: Not sure if this is helpful, but I've had my Fluke 1507 for a few years and so far haven't seen that issue.The Voltage function being right next to the off, I wonder if there isn't a bridge somewhere inside which is causing this?If there is I could imagine it causing the behavior (i.e. the "off" never being entirely selected because Voltage function it selected) same for turning on.I've got mine disassembled (though can only access the backside at the moment since the dial seems to connect to the front case and I don't want to unmount the thing unless there is an easy way to do)Let me know if there is anything you want me to measure to cross check.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 03, 2016, 05:52:01 pm
content: A number of comments and questions.Q1) Did you acquire this Fluke 1507 new or used? I'm assuming used from your wall of text, but want to double check. The answer helps determine if you qualify for Fluke's warranty or not.Q2) Schematics. You won't find any schematics for any current selling Fluke meter. There may be schematics of an older insulation tester that might yield some clues, but I don't follow this area so I would need to do some research. Fluke insulation testers aren't on my radar due to its high cost (MSRP $822CDN) and I can't find even broken ones on ebay in my usual $20 USD range.Q3) Can you upload clear focused pictures of both sides of the pcb and the rotary switch?Q4) Measure a 9V battery for 15 minutes with the rotary switch set to DCV. Does the meter turn off or does it still show a reading for the 9V battery?Q5) Measure a 1k ohm resistor for 15 minutes with the rotary switch set to ohms. Does the meter turn off or does it still show a reading for the 1k ohm resistor?Q6) Put the meter into the off position. Take out the batteries and leave them out for 2 minutes. Does the meter stay off or turn on when you put the batteries back in?Q7) Put the meter into the off position. Take out the batteries. Hookup a variable DC power supply and set it to 6V. Measure the current draw of the 1507. Report this number.Q8) Take out the batteries. Put the meter into the off position. Measure a 9V battery with the meter in this off position. Hookup a variable DC power supply and set it to 6V. Measure the current draw of the 1507. Report this number.Q9) In your picture, please identify the main IC. I'm guessing it is a MSP430, but don't know for sure.It should take you about 1 hour to complete and report the results.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 03, 2016, 06:05:14 pm
content: Found this threadhttps://www.eevblog.com/forum/testgear/fluke-1503-to-1507-conversion/where there are pictures of the 1503 which might be useful a bit later. You can never have enough clear focused teardown pictures IMHO.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 03, 2016, 06:11:29 pm
content: Quote from: dohyun on July 03, 2016, 02:40:31 pmOther possibilities include a broken via, trace, solder joint, bad passive component and/or ic/transistor that is not removing power to the main IC in the off position. Here the OP had a problem with his 787 and it was traced down to a bad via.https://www.eevblog.com/forum/repair/fluke-continuity-beeper-on-787-processmeter/Modemhead's blog contains a lot of Fluke meter repair case studies that have broken, corroded vias, dirty switches, etc.http://mrmodemhead.com/blog/all-posts/My suggested tests above might narrow down the problem. The current draw results when the meter is on the off will be the interesting ones (Q7 and Q8).

author: retiredcaps
author_rank: Super Contributor
timestamp: July 03, 2016, 09:35:13 pm
content: Q10) Put the meter into the DCV position. Take out the batteries. Hookup a variable DC power supply and set it to 6V. Measure the current draw of the 1507. Report this number. Let meter auto power off after 10 minutes. Report current draw after meter goes into auto power off mode. Move rotary switch from DCV to ohms mode. Report current draw after meter is in ohms rotary mode.

author: softwarejedimaster
author_rank: Contributor
timestamp: July 04, 2016, 03:32:14 am
content: Great stuff retiredcaps, here we go...A1) I'm not looking to get Fluke involved here. That would defeat the purpose. I want us to solve this one.A2) You are correct about the schematics - I already had a look and can't find any.A3) Pics are already available - see connected thread on 1503 to 1507 conversion below. But I will take some for identifying the main IC.A4) I measured a 5vdc source (Agilent E3614A) using sw position 1 (set to dc volts). The unit turned off after 10 minutes and would not come out of this mode by any key press or dial position change. I removed batteries for 30 seconds to restart.A5) I Measured a 100 ohm resistor using switch position 2 (set to ohms) and used the lock feature to maintain a continuous reading, otherwise I would have had to keep my finger on the Test button. This time the unit did not turn off. Perhaps using the lock test mode prevents unit from sleeping. The second attempt I pressed the Test button for a few seconds until the reading stabilized then released it to hold the reading. Ater 10 minutes unit went to sleep.A6) Unit turns on and displays the VDC mode.A7) current draw in "on mode" is 6.5 mA. Current draw in sleep/off mode is essentially zero or so small it is beyond my ability to measure, probably in the micro amp range. I don't have one of Dave's Micro Current meter add ons, I probably should have one.A8) I Measured a 5.00 vdc source using sw position 1 (set to dc volts). The unit was powered by an Agilent 6612C system dc power supply set to 6.00 vdc. The unit measured the 5.00 vdc supply correctly in the Volt switch position and the current draw was 6.7 mA.The unit measured the 5.00 vdc supply as 3.9 volts in the off position. Then 2 seconds later a strange thing happened. All segments started flashing rapidly for a bout 10 seconds then the display dimmed and finally turned off. Current slowly went to zero. Quickly cycling the unit from OFF to Volts (first two switch positions) yielded normal behavior. Occasionally all segments would display before powering down the display completely. I hate it when this happens. I needed to find a cause for the problem I was having, not fix the tester. Perhaps someone can shed light on something I am missing or not understanding.A9) The main IC is a Texas Instruments M430F427 as seen in the photo below.A10) The current draw in both volts and ohms mode when the auto power off occurs is zero or darn close to it as measured with my Agilent 6612C.After the 10 min of inactivity, the unit powers down as before, but this time after a range change or button press it takes about 10 seconds for the unit to again turn on. That's strange that it won't do this immediately.Thanks to retiredcaps for the troubleshooting layout questions - i'm learning more and more as I do this. Having a strategy is 99.9% of solving a problem.I have a working meter but I really don't know why...

author: retiredcaps
author_rank: Super Contributor
timestamp: July 04, 2016, 05:20:01 am
content: Quote from: softwarejedimaster on July 02, 2016, 10:10:05 pmIt is not clear to me from your description whether you actually took the rotary switch completely apart like modemhead in these two blog entries or not.http://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/http://mrmodemhead.com/blog/fluke-83-dmm-repair/

author: retiredcaps
author_rank: Super Contributor
timestamp: July 04, 2016, 05:47:54 am
content: So at first glance from the tests, it looks like the off position is identical to the Volts position in terms of the rotary switch position. Can we get close up shots of the rotary switch pcb (both sides) with the black rotors removed?Either the switch is mangled somehow or it is good, but the rotary switch off signal isn't being sent to the MSP430 due to a broken via, solder joint, bad passive component (open pull up/down resistor), or bad ic/transistor (stuck on high/low)?

author: Brainbox
author_rank: Contributor
timestamp: July 05, 2016, 07:57:31 pm
content: I bought my 1507 as defective because it had similar problems.Had to take the battery out to switch it off.The problem came from one of the push buttons which has a dirty rubber cap.After cleaning al the buttons with IPA everything wordked fine.

author: retiredcaps
author_rank: Super Contributor
timestamp: July 05, 2016, 08:05:05 pm
content: Quote from: Brainbox on July 05, 2016, 07:57:31 pmThanks for sharing.I would have never figured that one out especially remote troubleshooting.

author: softwarejedimaster
author_rank: Contributor
timestamp: July 12, 2016, 10:46:52 pm
content: Really sorry it took so long to get the pics up here. The first photo is the topside board. Not sure what it was doing when it started flashing and fading the screen, but weirdly enough it came good. I'm thinking more and more the rotary switch was to blame because that is the only area I concentrated in cleaning. But it looked very clean from the beginning.Special thanks to 'retiredcaps' for all the assistance he provided and the check list of possible stuff to look at. If i didn't do all the tests as he ordered, It probably will still be sitting on the "broken shelf"

author: retiredcaps
author_rank: Super Contributor
timestamp: July 12, 2016, 11:31:11 pm
content: Quote from: softwarejedimaster on July 12, 2016, 10:46:52 pmSo, it off in the off position now? You may want to verify that it is off by checking the current draw.

author: softwarejedimaster
author_rank: Contributor
timestamp: July 23, 2016, 12:21:54 am
content: Yes in the "OFF" position, current draw is zero.