Author Topic: Multimeters:Troubleshooting Fluke 75III & Fluke 77...repairable or disposable!  (Read 7347 times)

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Offline whitte

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Hello,

Wayne posting here....relatively new at this blogging.....however this appears to be a "excellent source" of credible information covering a very important and sometimes misunderstood tool that we find invaluable in our work, "the multimeter", and I could sure use some help and opinion.
 I am a Canadian (Northern B.C.) Inter-provincially licensed H.D. Mechanic/Millwright/Commercial Transport/ Automotive Mechanic.....been at this for 34 years +.

1) I have a old Fluke 77 that may have seen better days.....it has a new 9 v duracell in it....however it is doing a lot of strange things and is not useable........when swiched on to the ohm scale .OL. flashes constantly.....when the two leads are touched...same thing....switch it to diode testing and the audible tone comes on instantly whether the leads are touched or not......Numerals of.070 to .084 and more continually come in to view.....the 10 amp "unfused" scale that I use searching for DC battery draws is unuseable....when testing a 110 volt AC recepticle it reads something like 77 volts AC..................Garbage??? or is there some hope ???

2)Also I have a newer Fluke 77III......new battery....when switched to ohm scale....leads not touching it reads 13.02 to 13.28 is all over the map.....leads touching each other it reads  -226.3..to 805....759......all over the map......on diode test leads apart it shows OL....leads touching I get the beeping tone and.253.......volts AC  leads apart....I get .890......913......plugged in to a live 110v wall socket, I get form 164 to 185 Volts AC...all over the map as well.........once again....garbage or some hope ???

In my trades I have always preferred a good tough and simple analogue meter.....the movement of the meter wand tells me much more especially when internmittent  problems are being troubleshot....I could use currently, a good suggestion on a domestic brand analogue meter that is commonly viewed as tough, reliable, and relatively inexpensive. if such a thing still exists.......Tanx.

Offline mzacharias

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Wouldn't hurt to check the internal fuses and surge resistor and make sure the function switch contacts are clean. Probably not much more you can do for the Flukes, but used ones are all over eBay at reasonable prices, also you can pick up a good used Triplett or Simpson there as well. A new domestic meter of good quality would be over 300.00.

Online Aurora

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Always check visually for any evidence of battery leakage. I have seen many good meters rendered unserviceable or unreliable after a battery has leaked it's electrolyte onto the PCB. The electrolyte has two significant properties in this scenario, it is conductive, causing unusual circuit behaviour and readings, and it is corrosive, causing damage to pcb tracks and even open circuits in fine ones.

If battery leakage is the cause of your meters problems, you can sometimes repair minor track damage and flush the PCB with IPA to clean away most of the electrolyte. Sadly electrolyte does have a habbit of getting under components and even into the PCB material itself. If this has occurred, the meter will likely give problems in the future due to ongoing corrosion or unintended conduction between components or IC leads.

Hope this helps.

Offline PetrosA

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Some of the older Flukes I've seen (and worked on) are very dust friendly. You'll need two things to start - a can of compressed air (or a good compressor) and a can of contact cleaner. I'd open the meter and blow all the shit out of it, then check for more shit to blow out. IIRC, the function switch dial has retainers on it you'll need to press to take the dial off. The ones I've worked on had contacts pressing from both side of the PCB that you need to clean out. Hit them good with air, then contact cleaner,  then air again. If there's really stubborn dirt caked in there you may need to pick it out or use a sheet of stiff paper to work it out. Some of the contacts I've seen have appeared bent and I realigned them with tweezers. Once it's good and clean inside, I'd recommend taking the outside dial apart (usually has a retaining clip underneath) and getting all the crud out that makes it tough to turn the dial. Once it's clean, I use a very thin coat of Loctite Viper Lube on all the dial's plastic surfaces and reassemble. If the cleaning doesn't work, it's probably going to need to go back to Fluke.
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Offline whitte

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Yep, good points.....the Fluke 77 is pretty aged and dirty......the 75III has signs of battery leakage inside.....I wonder if cleaning doesn`t do the trick will it be worth sending the two in to Fluke for a estimate on repair or just break down and buy a newer one?

Offline Kiriakos-GR

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My father was an cars electricians , and me was close to become one, but I did escape  :D

Now at my 42 , I will offer an practical advice ..(Like what you do with engines.)

One good internal bath ( of the PCB ) of both multimeters , with clean alcohol ( the non colored that all the portable med kits have ) and a brush , it will remove any dirt or oil from them..

If they work correctly after the bath ... be happy.
If not ... replace them with better ones.

 

   


Online Aurora

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Whitte,

When it comes to battery leakage, most manufacturers will write off the PCB which in your case would make the units beyond economic repair. They don't want to risk future failures due to the reasons I have already detailed and professional organisations take a very dim view of electrolyte contamination of the PCB. I should start another thread on batteries that tend to leak as I have had nothing but trouble with Duracell 'Procell' batteries. They seem to like to either leak at the seals or in the case of 9V blocks, burst out of their casings ! I have a Fluke 52 thermometer where the 9V battery sits in the middle of the PCB without any leakage containment measures.... an almost certain write off if the battery leaks badly. Newer designs contain the battery in it's own little compartment and leakage damage is usually limited to the battery connectors. A note on battery leakage... I have seen electrolyte migrate down the battery wires, inside the insulation, and onto the PCB causing damage in the surrounding area .... it's nasty stuff and seems to travel further than you would expect ! NiCads & NiMh cells seem to do the same when old.

Back to the plot.... Give the units a damned good clean (taking care not to move any presets or trimmers in the process) with IPA or your chosen inert cleaning fluid and when completely dry, give them a test. If they still don't work and you don't wish to start tracing the faults yourself, I would suggest placing them on ebay as spares or repair so that someone can use the parts and you will recover some cash. I am not certain a Fluke 77 is really worth sending to Fluke as you can buy a good condition used one quite reasonably these days.  
« Last Edit: January 17, 2011, 11:50:06 AM by Aurora »

Online Excavatoree

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Hello,

1) I have a old Fluke 77 that may have seen better days.....it has a new 9 v duracell in it....however it is doing a lot of strange things and is not useable........when swiched on to the ohm scale .OL. flashes constantly.....when the two leads are touched...same thing....switch it to diode testing and the audible tone comes on instantly whether the leads are touched or not......Numerals of.070 to .084 and more continually come in to view.....the 10 amp "unfused" scale that I use searching for DC battery draws is unusable....when testing a 110 volt AC receptacle it reads something like 77 volts AC..................Garbage??? or is there some hope ???


Is this the older, square 77 (no series) or 77 series II?  If so, it sounds like the fusible resistor in the input is blown.  (someone mentioned the surge resistor, in an earlier post)

Here is a picture of the resistor in the meter:


Here are some other examples:  (several types were used over the years)


This resistor can be checked without removing it - it should be about 1K.

Let me know if this is it - the stock resistors are difficult to find, but parts meters on e-bay is the best way to get them.  (they are used in the old 8020, 8060 types, etc. also)  New, old stock resistors are expensive from other vendors, I'm not sure if they are available from Fluke.  

Or, you can use a replacement from Digi-key.  (I have a spare I can send to you)
« Last Edit: January 20, 2011, 02:55:16 AM by Excavatoree »

Offline saturation

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I still use my 35 year old Sanwa YX360 [ bought it when I was in the Pacific decades ago], for monitoring.  No batteries, not accurate by digital standards but very good precision for trend following.  Its still made in Japan and reasonably priced since its known to last a lifetime, but very hard to find in the USA.  I love how trouble free it is.

Alas, many USA available analogs, except Simpson, likely has Chinese meter movement, I wouldn't trust them after some year of use.  This Sanwa has proven itself by being over a 40 year old design, with some minor upgrades such as its now in a shock casing.

http://www.togbekal.com/products/sanwa/sanwa_yx360trf.htm



Beware, its a very popular meter in Asia, and its one of the most heavily counterfeited meters.  They are sold at Amazon, note the name Sunwa:



A USA source I could find:

http://www.homeschoolingsupply.com/united-scientific/science-equipment-fis-yx360trf.htm



....
In my trades I have always preferred a good tough and simple analogue meter.....the movement of the meter wand tells me much more especially when internmittent  problems are being troubleshot....I could use currently, a good suggestion on a domestic brand analogue meter that is commonly viewed as tough, reliable, and relatively inexpensive. if such a thing still exists.......Tanx.
Best Wishes,


Saturation

Offline whitte

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Some great input and advice guys...."Saturation" your Sanwa YX360 does appear from what I saw on the link to be a great simple tool exactly what I was looking for when doing field work.....I will keep my eyes open for one or eventually order one. 
Although am I correct to assume that is requires no batteries to work or does it mean they are included when purchased....I do not see how the OHM scale could work with out batteries ?

I have just purchased a Simpson 260-2P which is what I was originally looking for thanks to this blog site.

"Excavatoree" thanks for what appears as your correct diagnosos of a blown resistor in my Fluke 77....I will be away from my computor for a week or so.......I will have to pursue a replacement resistor upon my return.....Thanks for your input and help.....quite impressive.


Offline mrwildbob

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Excavatoree, Do you happen to know the part number at DigiKey or Mouser?  I have a Fluke 77 Series II that has the light tan resistor.  Mine shows an open.

thanx

boB


Is this the older, square 77 (no series) or 77 series II?  If so, it sounds like the fusible resistor in the input is blown.  (someone mentioned the surge resistor, in an earlier post)
Here are some other examples:  (several types were used over the years)

Or, you can use a replacement from Digi-key.  (I have a spare I can send to you)


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