Fluke 179 [Repaired] - Page 1
Forum section: electronics / repair

author: CJay
author_rank: Super Contributor
timestamp: October 31, 2016, 11:10:01 pm
content: So, eBay struck again and I'[m now the 'proud' owner of a Fluke 179 that's isbehaving badly.After a quick test it's defintely not happy,on DC range connected to a 1.5V AAA cell it displays -0.471V or, if /I reverse the test leads it displays -3.168V.On Ohms shorting the test probes ives me -3.209MOhm, diode/continuity test gives OL, probes shorted or open.DC amps flashes OL with nothing connected.On the bright side, the screen is in lovely condition and it's got a fairly new battery in it.The cal button has been damaged but isn't shorted, I think it 'developed' the fault and someone has tried to calibrate it out.There's no sign of flashover or gross damage on the board or either of the thick films, the MOVs and marked resistors measure OK.Any suggestions?

author: retiredcaps
author_rank: Super Contributor
timestamp: October 31, 2016, 11:28:15 pm
content: Quote from: CJay on October 31, 2016, 11:10:01 pmQ1) Can you list the measurements you got for the MOVs, PTC and fusible resistor?Q2) Can you provide clear focused pictures of the pcb (both sides)?Q3) Can you provide a close picture of the rotary switch (both sides)?Q4) Can you measure the current consumption of the 179 when set to DCV mode?Q5) Can you list the serial number?

author: retiredcaps
author_rank: Super Contributor
timestamp: October 31, 2016, 11:47:28 pm
content: Q6) Using another meter and with the Fluke 179 turned on and set to DCV, what is the input impedance of the 179? It should be around 11.11 Mohm.Q7) Using another meter and with the Fluke 179 turned on and set to milli DCV, what is the input impedance of the 179? It should be around 10 Mohm.Q8] Did you buy this "as is" or in "used, but working condition"?

author: CJay
author_rank: Super Contributor
timestamp: November 01, 2016, 08:13:00 am
content: Quote from: retiredcaps on October 31, 2016, 11:28:15 pmI'm just about to head out to work and don't have pictures of the board (yet) so I'll post those later but:Q1 MOVS were open circuit, 1K resistor was 1K, PTC, from memory, also read 1K which didn't seem right to me. Which one is the fusible (the 1K is a flameproof type, there's also a low value black resistor on the opposite side of the board, 2.5R I think, that's measuring OK in circuit) The smaller 2 pin thick film measures at 1M.Q2 No pics yet.Q3 As Q2Q4 2mAQ5 83490318Q6, Q7 open Circuit, I need to go back and check those input components again.Q8 Bought as faulty on the spur of the moment.All measurements made with a Fluke 77 (which is why I thought a new meter might be a nice update.)

author: retiredcaps
author_rank: Super Contributor
timestamp: November 01, 2016, 04:38:45 pm
content: Quote from: CJay on November 01, 2016, 08:13:00 amPTC around 1k ohm is fine. The fusible resistor in most modern Fluke meters is a light green colored body (see pic). I call it fusible because every Fluke service manual in the past as called it fusible and not flameproof. I'm not an expert to know if there is a difference between the two and Fluke's service manual states to replace with a fusible one (i.e. identical).QuoteLooks about right depending on which version of the pcb you have.QuoteNot part of the recall"Recalled units have a serial number below 79000000."https://www.cpsc.gov/Recalls/2002/CPSC-Fluke-Corp-Announce-Recall-of-Digital-MultimetersQuoteYes, this is definitely a problem. Check again.PS. Fusible picture fromhttps://www.eevblog.com/forum/testgear/fluke-179-teardown-photos/

author: CJay
author_rank: Super Contributor
timestamp: November 01, 2016, 06:50:29 pm
content: Well, to make a short story long, I checked all those components and traced the input jack up to the main multi-pin thick film but still to no avail, I could find no fault and was starting to worry I'd bought a basket case, if that thick film was duff then it's essentially scrap, especially as closer inspection of the board revealed it had been reworked at some point in the past.Funny thing though, inspiration struck as I realised I was tracing from the positive terminal, when I checked from the negative terminal, it's all open circuit.So, after a gruelling five minute fault finding session, I traced back the comon terminal (hindsight is a wondrous thing, see later) and found just after the current shunt something that looks like a chip inductor.Unfortunately it measured ok, so I traced on from there but found I'd lost continuity from the common terminal, sure enough, the inductor was cracked.For now I've soldered it back down as I can't identify the value, it's got no marking and my LCR meter won't measure it.Seems to be working just fine now with my cheap Chinese AD584 reference, and if the pics will attach....

author: retiredcaps
author_rank: Super Contributor
timestamp: November 01, 2016, 09:45:36 pm
content: Quote from: CJay on November 01, 2016, 06:50:29 pmGood job tracking down the problem. When the input impedance test showed open circuit, I was suspecting a corroded trace or some component going open circuit.I can just see that you have an older pcb due to the older rotary switch. I don't have an LCR meter, but modemhead has an older 179 and might be able to make an in circuit reading to get an approximation? He is on the road so it might take him a few days before he gets home?I will take a look at some of the older schematics for the 77 III to see if there are clues later on.At least two of Dave's eevblog meter BM235 has the same inductor problem right out of the box.

author: CJay
author_rank: Super Contributor
timestamp: November 01, 2016, 09:58:20 pm
content: Thank you very much for your help, I suspect I would have found it sooner or later but you defintely got me on the right path more quickly than I would have got there by myself.I'd like to replace the part with the correct one so any clues would be very welcome.

author: retiredcaps
author_rank: Super Contributor
timestamp: November 02, 2016, 05:37:21 am
content: Quote from: CJay on November 01, 2016, 09:58:20 pmWell, I looked through the Fluke 70 III service manual and there is no inductor at all. The Fluke 70 III series consists of some meters that are 3200 count and others that are 4000 count and use completely different chipsets.If we use modemhead's blog entries, we can see that the 26 III, 4000 count, has the inductor whereas the 23 III, 3200 count, does not. Unfortunately, there are no schematics for the 26 III.

author: ModemHead
author_rank: Frequent Contributor
timestamp: November 02, 2016, 12:26:32 pm
content: Quote from: retiredcaps on November 01, 2016, 09:45:36 pmIt'll be next week before I can check this out. Actually I don't have a "proper" LCR meter either, so any reading would be suspect. Probably a very small value inductor.

author: radioFlash
author_rank: Regular Contributor
timestamp: November 04, 2016, 02:09:00 am
content: I measured my 179 with the DE5000 LCR meter, and it shows about .5 uH.

author: CJay
author_rank: Super Contributor
timestamp: November 04, 2016, 07:13:00 am
content: Quote from: radioFlash on November 04, 2016, 02:09:00 amThank you.

author: EPTech
author_rank: Regular Contributor
timestamp: November 04, 2016, 09:46:24 am
content: Hi there,Nice find. It looks like a ferrite bead. These small SMD chip ones are usually just a straight wire with ferrite core around them, just like a bead around a cable. I doubt the DE5000 will be able to effetively measure the inductance of those kinds of beads. In fact inductance of a bead is not even mentioned in most data sheets, only impedance at a certain frequency or a impedance versus frequency plot. Other important factors are DC resistance and maximum rated DC current.If it is in the low current path, I would just replace it with any same size bead. Ex: 0,5 ohm on tot of 10 Mohm will not matter. If it is in the high current path, ex in the 10A range, it may be another story, but judging from the size of it, I guess it is not.

author: CJay
author_rank: Super Contributor
timestamp: November 09, 2016, 05:47:46 pm
content: It's definitely in the low current path so I'll pick up some low value chip inductors with my next order from RS.Another couple of possible issues, reading the manual from FLuke tells me I should be able to disable the auto power off by holding a button down and then turning the meter on but it doesn't work, the meter still powers off after a while (it won't 'wake up' unless I turn it off and on again, I assume that's normal too?).Similarly, the meter will only display 1.02.5 if I press the Hold button when turning it on, no matter which range I choose.Should I assume that certain features are only available in some firmware versions?The continuity beep doesn't work, the meter is missing one of the conductive rubber 'pegs' that connects the piezo to the main board, are they available or do I need to bodge something to suit?

author: retiredcaps
author_rank: Super Contributor
timestamp: November 09, 2016, 06:07:13 pm
content: Quote from: CJay on November 09, 2016, 05:47:46 pmAs I alluded to below, there are at least 3 different versions of the pcb that have significant changes.http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=264761https://www.eevblog.com/forum/repair/multimeter-repair-time-again!-fluke-177-reads-8-ohms/?allAs such, there are 3 different versions of the manual and I think Fluke only keeps the latest revision their website. I do link the older versions of the manual in the links above.QuoteThat is probably showing firmware 1.02.5. I think the latest models are firmware 2.x. None of the Fluke 170 series is user firmware upgradeable.QuotePossibly.QuoteI'm sure modemhead will suggest a bodge once he sees this thread.As I mentioned earlier, looking at the picture of your range switch, you definitely have an older revision of the Fluke 179 vs the one made today. There are significant changes from the 1st generation to the current model.

author: ModemHead
author_rank: Frequent Contributor
timestamp: November 09, 2016, 10:41:57 pm
content: The 179 I have here has a Rev 007 board, and it shows firmware version at 1.02.5 like yours. The power-on options in the manual do not seem to work, all I get is 4 dashes instead of "bEEP", "PoFF", "LoFF", etc.I measured 0.4uH on the inductor, ferrite bead, or whatever it is.Quote from: CJay on November 09, 2016, 05:47:46 pmHave an old TV remote control? Try cutting up a bit of the black stuff from the end of one of its buttons. If that doesn't work, I'd be inclined to solder a little spring on the PCB. Whatever you do, don't try to solder to the piezo unless you've done it before. It is easily destroyed by heat.

author: CJay
author_rank: Super Contributor
timestamp: November 10, 2016, 06:39:21 pm
content: Thanks, that's where I was heading with it but on closer examination of the pieze I realised it's been 'cleaned' in an attempt to make it work so I will need to test the piezo (should click if I touch it with another meter's probes set to ohms) and see if the 179 is producing a derive signal.Thanks also for confirming the operation of 1.02.5, that's exactly what it does on my meter, a little annoying as it seems it's not possible to wake it up without turning it off and on again but at least now I know it's not a problem or something I've done wrong I can live with it.I'll be putting an order in with RSWWW later today so I'll tack on a pack of inductors if I can find something suitable.

author: ModemHead
author_rank: Frequent Contributor
timestamp: November 10, 2016, 09:50:16 pm
content: Quote from: CJay on November 10, 2016, 06:39:21 pmI'm not so sure you'll be able to hear a click. 5Vpp 2kHz square wave from a function generator is better.

author: CJay
author_rank: Super Contributor
timestamp: November 10, 2016, 10:37:20 pm
content: Quote from: ModemHead on November 10, 2016, 09:50:16 pmhaving a function generator would be a requirement for that test though.I can hear a click, have to reverse the probes to discharge the piezo before I can hear it again but it's definitely there. I'll strip it down again tomorrow and check for the drive but I'm confident it will be present so I've nominated a sacrifical old remote to get the conductive rubber from.

author: CJay
author_rank: Super Contributor
timestamp: November 24, 2016, 01:21:38 pm
content: Well, after many days of trying to find time, I'm finally happy.A sacrificial remote control gave up a few of its conductive pads and I now have a Fluke 179 that makes a nice, loud and, weirdly, more pleasant sounding beep than my aging Fluke 77.Just for reference, there are companies which manufacture and sell replacement conductive rubber pads for repairing remote controls as well so if you're not a hoarder of junk and need to repeat this repair, there's still hope.So, Modemhead, Retiredcaps, thank you both for your help and is there any information about my meter you'd like for archives?

author: retiredcaps
author_rank: Super Contributor
timestamp: November 24, 2016, 05:52:17 pm
content: Quote from: CJay on November 24, 2016, 01:21:38 pmClear focused pictures of the pcb, both sides, in high resolution where we can read SMD silk screen components would be nice for future fixes since there are no schematics. You can divide the pcb into 3 or 4 sections to meet the eevblog size restrictions.