Fluke 287 23mA while off - Page 1
Forum section: electronics / repair

author: romantronixlab
author_rank: Regular Contributor
timestamp: November 23, 2018, 01:13:33 pm
content: Hello AllI have been wanting a Fluke 287 for a while. After much reading here the forums for a long time about the fluke 287-289 issues and information, I jumped in and a month ago bought a 287 that had the Lead Connection Warning off of eBay.To make the long story short, I was able to repair the Warning by replacing Q2 and the IR LED as recent 5 days ago, and all was within values (following a lot of reading from here, BTW great data).Installed a new set off fresh Energizer Industrial batteries but after a period of 4 days the meter wanted more new batteries. How is that even possible?Power draw measurements were taken in off state at 24.5mA, I read at another post it should be at around 50uAHave read about the super capacitor issue but this meter has a different revision number and its “capacitor” looks more like a battery, when I took it apart it measured about .8v or 1v and no signs of leakage. Could it be it took all that power to recharge the capacitor or battery?Never came to me I would use a Fluke 87V to do tests on a Fluke 287The capacitor/battery in my 287 is like in this post by edgeloghttps://www.eevblog.com/forum/testgear/annoyed-with-the-fluke-289/msg1809107/#msg1809107Edit: Any way I could find a replacement of the Capacitor/battery as what was pictured at the above link? Thank You all

author: evava
author_rank: Regular Contributor
timestamp: November 26, 2018, 12:44:57 pm
content: First you need to measure power draw (current draw) in OFF state without super capacitor/battery, and then if current is about 50uA you should accuse super capacitor/battery.6V x 0.025A = 0.15W - maybe you could see the culprit on the board through infra camera ?

author: coromonadalix
author_rank: Super Contributor
timestamp: November 26, 2018, 09:32:57 pm
content: you can find super capacitors on Digikey, Electrosonic, Mouser, mine came from Digikey0.33 farad at 5.5 volts at 3.45$ way overkill, normally they are 0.1 farad if i recall correctlyhttps://www.digikey.com/products/en/capacitors/electric-double-layer-capacitors-edlc-supercapacitors/61/page/1You will have to do legs bending or buy a radial capacitor and do some fitting ??

author: romantronixlab
author_rank: Regular Contributor
timestamp: December 05, 2018, 02:58:32 am
content: Sorry if this update sounds rough its the third time i write this.Finally had some time tonight to verify what was suggested. Before following your suggestions I installed a new set of batteries on Sunday, set the time and date, left it for about 6 hours in off mode, then took them off let it rest for about half an hour maybe more, then reinstalled the batteries and turn it on; the 287 asked again to configure the date and time.Desoldered the secondary battery it measured only 1.5v no load, it appears to be a Panasonic 5v rechargeable.It is an actual supercap half charged.I was able to confirm the new version of the 287 is no longer using a supercap like some have suggested. BT1 as it is marked on the new revision is aML621(ML Series) Coin type rechargeable lithium batteryThe meter off is reading 23.4mA power consumption and turned on doing nothing consumes around 44mA.After leaving it to get to ambient temps there where only two areas I could see a difference in temps but not much in my opinion but I could be wrong.One near the tantalums they measured 9v (provided by PSU) and another temp difference near the IC.

author: romantronixlab
author_rank: Regular Contributor
timestamp: December 06, 2018, 01:10:05 pm
content: Good Day to all,This morning had time to play around with the test gear, and took my LCR meter out, to test the, what i now know is a 5v+/-.5 supercapacitor and not a battery like i posted in my previous report, to take some values out of the thing.Since there is no information about who manufactures this or any datasheet or part number for it, I did some tests in different frequencies 1khz, 10khz and 100khz, lower than that provided no data or went OL, and basically it hovered around 30-37pF depending on the frequency but what did catch my eye was that the resistance was high in the M.After that i proceeded to charge the cap to its intended voltage 5v but after 1hr it never got to the 5v when measured no load.As there is no data about this supercap and the voltage behavior could we infer that this is bad and causing the power consumption? This is my first supercap experienceand know nothing about it.

author: romantronixlab
author_rank: Regular Contributor
timestamp: December 07, 2018, 12:44:47 am
content: Third update;Dedicated a bit more time to this thing this afternoon, and studying the parts and circuit found that something was keeping power to a circuit that had a constant 3v to the supercap pads. I also followed some voltage reading on most of the TP's, and the voltages where way off. I had my doubts about one particular point, CR17 is aBAT54S Schottky Dioderight near the supercap, and when tested it tested good on pin 1-3 but not good on 2-3, I think that's where the problem is. Without CR17 now the TP's voltages are close to correct values.But having previously replaced Q2 and now finding CR17 also in need or replacement, I think I will test all similar components.Will keep you updated.Edit: What type component is 8H in VR5, I assume VR is for voltage regulator but I want to get the right part. the component in VR5 is discolored and probably not working properly.(haven't tested)

author: romantronixlab
author_rank: Regular Contributor
timestamp: April 21, 2019, 07:28:10 pm
content: Hello allIt has been a while since my last updateI thought I had it all sorted out and ready to post the solution on this one. Replaced a 5v regulator U17 and VR5 because they were not working stable. Put the thing back together to a certain point powered good as usual and measurements are accurate, but still, the same 23ma consumption when "powered off".Followed I did more TP voltage tests just in case I missed something but all is within values.Later followed a voltage test around tantalum capacitors and found a discrepancy in the readings around the LP324M that are just reading 1.28vTestC61 17.55 > 15.45C58 1.245 > 1.28C56 2.493 > 1.28C59 20.03 > 1.28C62 18.79 > 1.28These readings are done on the capacitor. But if I make readings on the opamp pins the readings apparently what are “normal”.PIN4 V+ & PIN11 GND > 20.5PIN1-2 & PIN11 > 19.3PIN7 & PIN11 > 18.1PIN14-13 & PIN4 > 19.3PIN 8-9 & PIN4 > 18.1Because of a lack of schematics, I cannot figure out why C61 is the only capacitor reading a voltage, at first I doubted LP324M but the voltages from the pins say otherwise. Could it be something is shorting, or IC not properly controlling the polarity, just saying?Reference fromFluke 289 not quite sorted.

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 25, 2019, 01:09:12 pm
content: Email me atmark_zacharias@sbcglobal.netAnd I can send you .JPG's of the service manual.It is for the US military 189ii which apparently is the same as a 287.