Fluke 189 Meter appears to be internally shorted

[sigp232]

We have a Fluke 189 meter that was put in the surplus bin and I wanted to check it out before we get rid of this robust meter and need to buy a replacement.  I replaced the batteries in the meter and have attempted to use the meter.   The meter powers up fine.  I can select each function and the screen is fine.  Fuses are good.   

Here is the funny part.  The meter gives all zero's for AC and DC voltages.  Additionally, when I select ohms, instead of reading OL, it gives me 0.00 ohms.  I have checked the resistance of all the inputs to the board and everything looks fine.  It is like there is an internal short in the meter preventing it from reading any values. 

I have also checked the MOVs in the circuit and they appear fine.  I have also checked the large resistors on the board and they appear correct.  The input jacks all appear snug and they do not appear to be broken (I do have a new input plug assembly so I can replace the existing unit, but that does not appear to be the issue.  The ultra cap does appear to have typical corrosion, but does appear to be working from what I have read.  I will need to verify current readings the next time I am in the lab, but the meter does correctly sense leads depending on what function I am using.  I have also tried different test leads. 

I am running out of ideas and I apologize if this topic has been covered, but I have attempted to do a pretty comprehensive search and also read numerous threads on the repair of other Fluke meters.

Any thoughts? 

Thanks

Nate

[Arhigos]

blue varistor are typically what's causing multimeter to read shorted. Did you checked them with insulation meter at 1kv?? also input thermistor or resistor can cause that.

In most cases this is just something around input protection blown.

[sigp232]

I will double check the MOV's on Wednesday when I am in in the lab. 

Thanks

Nate

[sigp232]

The MOVs are fine.  I will have to keep searching

[bdunham7]

No schematic may make it a bit tough as we'll have to assume a few similarities with other known designs.

If you can connect it to a bench meter and measure its input impedance on different DC volts ranges that might help understand what is going on.  On 5V you should see ~11.0M, on 50V ~10.1M, 500V 10.01M and so on.  Then on resistance ranges, look at the output voltages measured by the bench meter.  On the 500R, 5K and 50K range I get ~5.0V, then I get 1.0 volts on the higher ranges.  Or something like that, I can recheck for you if there are any questions.

If you get normal changes in these values but the display consistently reads all zeros, that would indicate a failure internal to the main IC provided the 189 is like some other meters.  But I don't know that for sure.  You can also try the AC ranges (not for input impedance--just test them with an input) to see if you have any response there.

[Electro Detective]

60 cents worth:

I reckon someone tried DIY calibration and stuffed it up,

or unit was put in that mode by accident and random WTxxxx! button pushes and panic dial rotations knackered it

or the bearded supercrapacitor is causing havoc whilst in circuit

or combination of both above, and one beer three many..   


You will not get a better all rounder 'user friendly' meter, with 100khz AC performance (!!)  =   it's worth saving

or sell or donate to someone who will give a go


These items do not belong in the landfill for a while yet,

nor should be subject to 'dumpster it' clueless corporat decrees   


Surely there must be some 'out of warranty' Fluke specialists in the U.S. to send it to, 
for a fix and cal quote 

[joeqsmith]

I traced out bits of the front end and show them during this video.    This meter has some odd problem like that after a wannabe hack lost one of the wiper contacts when they had it apart.