Another Fluke87 problem

[planenut2000]

Sorry im new here and if my problem has been discussed before i apologize.
My fluke 87  shows a -34Kohms on the ohm scale with no leads. it also shows -4 volts on the dc volt scale, again with no leads.
All other positions look normal. I had it sent into a repair facility ( not Fluke Co.) They weren't able to find anything wrong with, but installed a new lead jacks.
Any ideas on where to look?

[retiredcaps]

Take it apart and post clear focused pictures of both sides of the pcb.

If you're lucky, it could be a simple IPA bath cleaning or it could be your input protection components are bad.

Do you have another working meter to make measurements of the input protection components?

[planenut2000]

Thanks for the replay, i do have another meter a fluke 88, buts its at work at this time. it will be a few  days until i can get it.

[planenut2000]

Here are the pictures

[planenut2000]

2nd pic

[retiredcaps]

While you wait for the Fluke 88, take a look at modemhead's post and check the rotary switch for debris.

http://mrmodemhead.com/blog/fluke-83-iii-rotary-switch/

http://mrmodemhead.com/blog/fluke-83-dmm-repair/

Since you mentioned they installed new lead jacks, this might interest you as well.

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

There's a lot of good info on modemhead's site.

[retiredcaps]

When your 88 arrives, use

http://bama.edebris.com/download/fluke/87/fluke-83-85-87-multimeters-sm.pdf

pages 45 and 46 for your references.

Check R1, R2, RT1, E1, RV1 and RV2.  Their resistance reading should be as follows.

R1 = 1K
R2 = 909K
RT1 = 1.5K
E1 = 0L
RV1 = 0L
RV2 =0L

Report your findings for the above.

[bdunham7]

In addition, what does it read on DCV with the input shorted?  And can you use the other DMM to actually measure the voltage at the 87 input jacks to see if the 4V is actually there and if it changes at all when measured?

[planenut2000]

i put the 87 back together to check the voltage on the dc scale. when the leads are shorted it drops to zero volts. when the voltage is measured with a cheap 2nd meter, the voltage is pulled down to a little under 3 volts and is displayed on both meters

[planenut2000]

R1-reads 882mega ohms
R2-3.4 k ohms
E1- 1.4kohms
RV1-OL
RV2-OL
Not sure which one is RT1

[planenut2000]

If RT1 is yellow and looks like a capacitor with a slot cut in it, then measured from the other side of the board it is open(OL)

[bdunham7]

I think that's it.  You can replace it with a 1.5K resistor(or so, anything in the ballpark will work fine) for testing purposes.  I'm pretty sure your troubles won't end there, but you have to start somewhere.

[planenut2000]

looks like the R1 and R2 are also way out of range

[planenut2000]

and the E1 is out of range also

[planenut2000]

I think 2 components are misplaced
the E1 and RT1 are in different locations on this meter compared to another pic of a 87 on this site.

[planenut2000]

Heres the pic of another early Fluke 87

[bdunham7]

I think 2 components are misplaced
the E1 and RT1 are in different locations on this meter compared to another pic of a 87 on this site.

I wouldn't jump to that conclusion--the boards are different revisions and the manual I'm looking at is earlier than your meter.  You should follow the traces and see how they are connected--the actual schematic is unlikely to change all that much.  If the PTC and GDT are actually misinstalled there must be a story there somehow.

Here's the schematic I'm looking at:

[retiredcaps]

R1-reads 882mega ohms
R2-3.4 k ohms
E1- 1.4kohms
RV1-OL
RV2-OL
Not sure which one is RT1

Replace R1 with anything close to 1K ohm and retest your meter.  If meter works, then we can get a proper rated replacement.

[retiredcaps]

If RT1 is yellow and looks like a capacitor with a slot cut in it, then measured from the other side of the board it is open(OL)

That's your spark gap and it should be 0L.

[planenut2000]

I will try to find a 1 kohm resistor locally to try, Thanks for your help!!
Theres something im not understanding however. Look at my pic attachment. why is the r2 position a 3.5kohm resistor and the r1 resistor is the 909 kohm

[bdunham7]

You simply need to either find a manual that matches your revision or just try and work through with what you have.  I would start by concentrating on any components that don't measure as marked and worry about the remote possibility that someone has mixed up the parts later.  If you measured the components using the board drawing I have, it looks like everything is fine except that the 909K resistor is mostly open--or did you misread  your meter and you meant 882 kiloohms, not megaohms?  In that case, all 4 input components seem fine, or at least good enough not to cause your issue.

And are you sure yours is an original 87 and not an 87-3?

[planenut2000]

I doubled checked the R1 reading and its mega ohms.  I purchased it used from an ebay seller, and he said he repaired it. It never seemed correct in the readings. Im used to my trusted fluke 88, all the readings on that are pretty stable.  So after putting up with the flakey readings for a while i sent to a business in either S. carolina or N carolina that advertises fluke meter repair. They said they found nothing wrong but replaced the input jacks just because they fail sometimes. When i got it back from them it didnt seem much better. But my wallet was $150 lighter. After i ignored the fluke for several months i tried using it and found the problems im trying to fix now.
Im an auto mechanic and aircraft mechanic and i dont like to give up on things until i get to the root cause of the issue.

[planenut2000]

just 87

[bdunham7]

These look more like a match with your -AC revision?

[planenut2000]

Thank You very much, that exactly what i have. So my R2 is out of spec.