Fluke 179 repair

[jmbinette]

Hi to all,

I have a Fluke 179 laying around that was given to me and I would like to repair it.
Cannot find a service manual but hope some of you could help me.

Unit power up fine, but most functions don't work properly.
As you ca see on the pictures, there's a sign of heat/burn on the back of the selector button but cannot find the same thing significantly on the PCB.

When is continuity mode, unit does not beep and start by reading "OL". When I short the probes, nothing happens and reading stay at "OL"
On resistance measurement, when I short the probes, reading is -3.204MOhm
Upon entering the mVdc measurement mode, the reading goes from 480mVdc gradually to 0.1mVdc
On mA AC mode with no leads attached, reading start at "LEAD" then 14mA AC and over the time of 1 minute gradually to 0.10mA AC

Does these numbers/readings ring a bell for you?

[jmbinette]

More pictures

[jmbinette]

More

[retiredcaps]

Suggestions.  With another working meter measure the following (Fluke 179 should be powered off and 9v battery removed):

1) The three blue MOVs, to the right of the rotary switch, should all measure infinite resistance using another multimeter.

2) The green fusible resistor just below the three blue MOVs should measure roughly 1k ohm.

3) The black PTC just above the volt/ohm jack should measure aroudn 1.1k ohm.

4) Report all your readings.

[jmbinette]

Thanks for the help !

1) Correct, all 3 are infinity
2) Correct, 996 Ohm
3) 1.224k Ohm

[retiredcaps]

Readings 2-3 look okay.  More.

5) Power on 179.  Put it into VDC mode.  With another meter that can measure up to 20M ohm, measure the input impedance of the Fluke 179.  That is, put working meter into resistance mode.  Put the working meter black probe into the 179 COM jack.  Put the working meter red probe into the 179 volt/ohm jack.

It should measure around 11.11M ohm.

Something like

https://www.eevblog.com/forum/repair/fluke-87-i-repair/msg390462/#msg390462

6) Put the Fluke 179 into mVDC mode. With another meter that can measure up to 20M ohm, measure the input impedance of the Fluke 179.  It should measure around 10M ohm.

7) The cheap free Habour Freight meters can only measure up to 2M ohm.  When testing #1, what meter are you using?  We need to know its maximum ohm reading.

8] If you measure a 1.5 AA cell, what does the 179 show in VDC? 0? 1.5?

[coromonadalix]

hi
I would clean the rotative switch, deoxidize it, check the contacts if they have roasted / heated due to a current overload, intrigued by the traces left on the white case ??

Check the small rectifier bridge and the black power resistor near it
 
Near the shunt resistor there is a black smt part, and a brown smt capacitor, not sure its a protector or a diode    the same thing there between the rectifier bridge and the resistor, protector or a diode ?

Checked the fuses to see if your inputs impedances measurements are fine ... 

[coromonadalix]

check this site,  may help in some ways ??

http://www.schematicsunlimited.com/f/fluke

[jmbinette]

@retiredcaps

5) Infinity on the working meter and -0.432Vdc on the 179
6) Infinity on the working meter and -413.5mVdc on the 179
7) My other meter is a Fluke 12, supposed to be able to read 40M Ohm. (?)
8} AA cell on the Fluke 12 1.583 Vdc and -0.443Vdc on the Fluke 179

Readings 2-3 look okay.  More.

5) Power on 179.  Put it into VDC mode.  With another meter that can measure up to 20M ohm, measure the input impedance of the Fluke 179.  That is, put working meter into resistance mode.  Put the working meter black probe into the 179 COM jack.  Put the working meter red probe into the 179 volt/ohm jack.

It should measure around 11.11M ohm.

Something like

https://www.eevblog.com/forum/repair/fluke-87-i-repair/msg390462/#msg390462

6) Put the Fluke 179 into mVDC mode. With another meter that can measure up to 20M ohm, measure the input impedance of the Fluke 179.  It should measure around 10M ohm.

7) The cheap free Habour Freight meters can only measure up to 2M ohm.  When testing #1, what meter are you using?  We need to know its maximum ohm reading.

8] If you measure a 1.5 AA cell, what does the 179 show in VDC? 0? 1.5?

[retiredcaps]

I would clean the rotative switch, deoxidize it, check the contacts if they have roasted / heated due to a current overload, intrigued by the traces left on the white case ??

Yes, check the switch.

Checked the fuses to see if your inputs impedances measurements are fine ...

The fuses won't be the cause of these faults.  A bad fuse only affects current reading, not voltage/ohms/diode.

[retiredcaps]

check this site,  may help in some ways ??

http://www.schematicsunlimited.com/f/fluke

You won't find any schematics for the 17x series anywhere on the Internet.

The predecessor to the 17x was the Fluke 7x III series. There are schematics for that series and the input protection is similar to the 17x.

[retiredcaps]

5) Infinity on the working meter and -0.432Vdc on the 179
6) Infinity on the working meter and -413.5mVdc on the 179
7) My other meter is a Fluke 12, supposed to be able to read 40M Ohm. (?)
8} AA cell on the Fluke 12 1.583 Vdc and -0.443Vdc on the Fluke 179

I have a Fluke 12 and I would trust its readings.  Obviously, all the above readings are incorrect.

If the switch is bad, it will affect the readings.  There could also be a bad via/solder trace or open component.  I don't currently have 179, but I do have a 175.  If I have time, I will check some readings tomorrow to help narrow down where the fault lies.

[floobydust]

don't forget the cracked ferrite-bead problem that can occur on these, I would check it with a working ohmmeter.

pic taken from: https://www.badcaps.net/forum/showthread.php?p=773106#post773106

[retiredcaps]

don't forget the cracked ferrite-bead problem that can occur on these, I would check it with a working ohmmeter.

I saw a pic here https://www.badcaps.net/forum/showthread.php?p=773106#post773106

I was just looking for those threads as well.

https://www.eevblog.com/forum/repair/fluke-179-not-working/

https://www.eevblog.com/forum/repair/fluke-179-76688/

[jmbinette]

I will clean the switch tonight and check that ferrite bead.

What kind of reading I should get with my ohmeter ?
I saw 100Ohm on the badcaps.net post

[EDIT] I read continuity (0.2 Ohm) accros that bead. This is measuring while on the board, should I desolder or it confirms it is bad ?

[retiredcaps]

[EDIT] I read continuity (0.2 Ohm) accros that bead.

A bead should read about that value (0.2 ohm).  What you are looking for is if the bead makes contact with the pcb on both sides.

[jmbinette]

Yes I meant the "ferrite bead", not solder bead.

It makes good contact with the board but I will double-check ..

[retiredcaps]

Wait.  A generic ferrite bead reads around 0.2 ohms.  The inductor should be around 100 ohms.  We have some confusion on what that part is actually called?

[jmbinette]

Sorry for that.

When measuring this part directly on the board (and make a good contact with PCB), I get 0.2 Ohm

[floobydust]

DC resistance of that ferrite bead is very low, under 0.01 ohm but at AC high frequencies 100MHz up it is 100 ohms and that maybe a confusing number.
You should get continuity without too much force, or follow the PCB traces and measure away from the ferrite.
If you push hard with probes/bend the PCB, a cracked ferrite can start working.

[jmbinette]

Wow thank you guys ! You were perfectly right !

When I was measuring, even the slightest pressure was enough to make good contact with the PCB. testing with the traces, I found the problem.

unsoldered, cleaned, resoldered and Voilà !

Thanks again ! I have a brand new 179

[retiredcaps]

Good score for a little bit of solder and IPA.  Is it spot on with the Fluke 12?

[jmbinette]

.002Vdc difference between the two on a AA battery (using the same probes)

Pretty happy with it !

[HoySum]

Hi, i also faced similar problem however mine is due to battery leakage and i hope you gurus can help me out. Please see picture and there is some parts missing from the circuit board below the com input terminal. Please help me identify the parts missing.
Thanks in advance

[retiredcaps]

Hoysum continued this at

https://www.eevblog.com/forum/repair/need-help-in-repairing-fluke-f179-due-to-battery-leak/