Fluke 89 IV - powers up, measures nothing

[4thDoctorWhoFan]

Going by your pictures, the input block seems to be very dirty.  You might have some contamination within or even under the input block especially since you mentioned it got wet.
I would remove the input block and give it a good cleaning along with the PCB under the block.  Or leave the input block connected and submerge it in some IPA and let it soak for a little while.  Make sure you let it dry before retesting.

[retiredcaps]

Going by your pictures, the input block seems to be very dirty.  You might have some contamination within or even under the input block especially since you mentioned it got wet.

Good suggestion.  I totally forgot to suggest that.  See

http://mrmodemhead.com/blog/gallery/fluke-189-clean-up/

[asdqwerty]

The input-block is the part where the water entered the 89, and also the part where it was most wet.. and the only part not totally disassembled..
I'll give it a look..

[retiredcaps]

Note the use of paper towels soaked with IPA and then cotton buds to dry.

http://mrmodemhead.com/blog/wp-content/gallery/f189_00/F189_021.JPG

BTW, I'm now reminded that modemhead fixed a 187 that had wonky input jacks.  It was a mechanical lug/broken solder problem.  Similar to his blog post below

http://mrmodemhead.com/blog/fluke-80-series-jack-assembly-rebuild/

I'm not saying your 89IV has wonky input jacks because your VDC seems to work 90% of the time.

[retiredcaps]

Free_electron fixed this Fluke 189 wrt to the input jack block.

https://www.eevblog.com/forum/repair/fluke-189-teardown-repair/

[asdqwerty]

I can easily get a good reading with another ohm-meter, from within the inputblock to the rear side of the pcb, or to the MOVs or resistors. So I guess it is something else.. Worth a try though..
Thanks for all the inputs anyway

[retiredcaps]

Maybe worth mentioning... the multimeter was exposed to rain late last summer. It was forgotten outdoor, and quite wet. But after drying, it has worked flawlessly since. At least 8-9 months..

I'm just curious how you dried it?  Air dry or did you scrub the entire pcb with 91% IPA?  How did you get the water out of the big ICs?

[asdqwerty]

I remember it was most water around the input-block, so I guess I was shaking the pcb and then using a hot-air blower to dry that part, and some paper-towels.
No IPA, only air. Can't remember I spent time drying other parts. Maybe it was positioned in such a way most water was in the bottom...
It was left outdoor on a friday, I got it back following monday, can't remember when the rain set in, or what time that other guy found it. But it sure was wet for many hours.
But since it powered-up and started working after some drying, I have just forgotten about the drying process. Only remember I spent some time with the input-block. And I'm quite sure I removed the LCD, and if it was water there I must have used paper and hot air..

 

[retiredcaps]

Any pictures or results from taking apart and/or cleaning the input block?

[retiredcaps]

Additional comment:

Measurement picture 2:
If I on the faulty 89IV press "range" and cycle through the manual ranges, it affects the readout on both meters.
Like:
519K - 1.13Vdc
0,12M - 0.38Vdc
2.44K - 4.83Vdc
37.5K - 2.83Vdc
Auto - as picture

It also had a small impact of the current measurement, leading to decreasig current to almost zero.

Well, at least the readings aren't 0 ohms.  The readings, obviously are way off, perhaps due to contamination on the pcb or input block?

[macboy]

The 89 IV has a lifetime warranty. Why are you messing about with it?

[retiredcaps]

The 89 IV has a lifetime warranty. Why are you messing about with it?

I see a lot of people make this common assumption about Fluke's lifetime warranty. Fluke's "lifetime" is a marketing term.  Details in screenshot below. 

[asdqwerty]

I called Fluke, asking for advice. They said this unt is more than 15 years old. It better to buy a new than sending in for repair. Nobody said anything about warranty.

--

I have not disassembled the inputblock. It seems to be a compact-piece, and has 8 soldering point.
However, when I take another ohm-meter and put one test probe in the inputblock, and the other probe on the soldering-point on the rear, or a component along the input-stage, I get very low ohm reading, so I concluded there's no problem along that signal path...(?!)

[retiredcaps]

A lot of those side by side readings are obviously wrong suggesting there might be leakage current somewhere.  If it were my meter, I would have already desoldered the input block and cleaned it.  I buy abused/used meters and have seen what pcb contamination, however small and not visible to the eye, can do in terms of funny readings.  There are a number of cases here where we have helped users fix their multimeters with funny readings just by a good IPA bath.

You have nothing to lose but 15 minutes of your time because this Fluke is not under warranty.

[asdqwerty]

That's right. It doesn't work as is, so it can't be any worse.

I'm gonna desolder the input block and give the pcb a good IPA bath.

[retiredcaps]

I'm gonna desolder the input block and give the pcb a good IPA bath.

I'm not saying this is going to work, but if we eliminate this as a possibility, then we can move on to other things.  If the readings also change that gives us a clue too.

BTW, I still can't shake the feeling those two solder MOV points should be open circuit when the 89IV is powered off.  However, I have been fighting a cold for almost 5 weeks so I may not be thinking clearly or I just don't understand how it works in the 89IV.  I have no formal electronics education. 

[oldway]

My 87IV had more or less the same problem: no reading at all.
The black binding post of input block was defective (broken and interrupted)
As this input block is very expensive and I don't use current inputs, I mounted the input block of the wrong way (rotated of 180°) and it work again. (see picture)

[Monkeh]

BTW, I still can't shake the feeling those two solder MOV points should be open circuit when the 89IV is powered off.  However, I have been fighting a cold for almost 5 weeks so I may not be thinking clearly or I just don't understand how it works in the 89IV.  I have no formal electronics education. 

No power attached is not necessarily the same thing as being switched off.