Author Topic: Repair Fluke high end DMM. Got rolled on a used one.  (Read 5750 times)

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Offline viper

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Repair Fluke high end DMM. Got rolled on a used one.
« on: November 06, 2015, 06:15:31 am »
Just needed to upgrade my meter and spotted a used one that fit my needs.  Just my luck, it does not work right.  ACV and the "component test" modes do not work.  All other modes will display first which ports to connect leads to, then value displays.  When in ACV and component test, the screen stays blank but does light up the back light to indicate the circuit is otherwise powered.   The meter has a self test and checks itself mostly fine or at least no error messages but is supposed to display a graph and does not. 

The meter is older but was the premier hotrod over a decade ago.  The PCB is clean, nice, and well built.  No visual indication of issues.  I am really hoping this being a high end meter, it would have good protection and I don't have an otherwise dead proprietary chip.  Fluke will not even work on it but I have at least asked for a schematic. 

To be honest, I have repaired a lot of different circuits, but never a multimeter and I don't even know how they are constructed.  The Fluke here is a tri level board so very hard to trace things. 
 

Offline retiredcaps

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #1 on: November 06, 2015, 06:22:31 am »
Which Fluke model?
 

Offline viper

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #2 on: November 06, 2015, 07:20:17 am »
Sorry, this is an 867B
 

Offline retiredcaps

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #3 on: November 06, 2015, 08:04:02 am »
1) Does DCV work?
2) Does ohms work?
3) When you measure mains, do you get 110V to 120VAC?  If not, what does it show? 0? A picture of the problem would help.
4) Service manual with theory of operations, BOM and schematics at

http://assets.fluke.com/manuals/863_867_smeng0000.pdf

5) Does diode test work?
« Last Edit: November 06, 2015, 08:11:37 am by retiredcaps »
 

Offline Jacek_Paw

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #4 on: November 06, 2015, 09:29:28 am »
Hi,

I had simmilar problem with my 867B and it was caused by dirt on contacts of range selecion knob.
I have just cleaned everything with isopropyl.

 
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Offline TiN

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #5 on: November 06, 2015, 10:12:46 am »
[offtopic]I'm probably sick already, as I thought "Yay, somebody trying repair 8508A", when read words "high end fluke DMM" in topic name...  :scared:
[/offtopic]

Where's hospital for volt-nuts?  :palm:
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Offline viper

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #6 on: November 06, 2015, 01:19:31 pm »
I can provide a pic if needed but as mentioned, in ACV, the display is mostly blank.  There are some boxes that are drawn identically in each at the bottom of the display that would hold words for the softkey functions in each mode.  Those boxes are the only thing present.  There is no data, nothing else at all displayed in ACV. 

Yes, DCV and ohms work as they should. 

To me, it almost seems like there is a switch loop that is not even turning the ACV on BUT as I mentioned, the meter certainly lights up the backlight when ACV is switched so I know something goes hot in that mode.  I am concerned of a software or program glitch on the MCU but hoping this is something simple. 
 

Offline ModemHead

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #7 on: November 06, 2015, 01:32:24 pm »
I don't know much about this meter, it's too complicated for me.  :P

I had simmilar problem with my 867B and it was caused by dirt on contacts of range selecion knob.
I have just cleaned everything with isopropyl.

Function selection is done by the PTF (black stuff) switch contacts on the back side. Switch position is encoded by a voltage level from a divider type arrangement.  Maybe something is wrong with the contacts or resistors in the chain?  If you can locate TP22, you should be able to see if it's working correctly.

Edit: added schematic clip
 

Offline viper

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #8 on: November 06, 2015, 01:57:00 pm »
Thanks so much for the help!!!  Yes, I too am thinking something along the lines of rotary switch because this is not like there are issues with the input protection circuits because it never gets that far.  As well, all other functions work perfectly, self test does not find errors, etc.  It almost seems as though there is not a reset signal sent somewhere to tell the processor these modes are turned on. 

However, the meter certainly powers up the display in ACV which leads me to think that possibly the rotary switch has double contacts and one is common for all modes to turn on display power, another contact is used for each mode to tell system which mode is running. 

I have checked the resistors around the rotary switch as well as tried some testing around switch and not finding much yet but there are some contacts that appear to be on bottom of switch and have a hard time figuring out how it works visually. 
 

Offline viper

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #9 on: November 06, 2015, 05:30:29 pm »
And....  Thank you to all that contributed!  After seeing the schematic and someone pointing out the functions of the rotary switch, I cleaned things up and slightly reformed the contact arms on the switch and we have a winner!  That black stuff is a little confusing as it has resistance through it.  I ended up pulling the disc off the back and cleaned it all.  I think I was seeing upwards of 2000ohms on one of the problem modes but after repair I was seeing about 600ohms through that black stuff from trace to trace before the series resistors.  I decided they were all testing about the same so I should try it because otherwise, the switch was not causing it.  It worked!

So I got a deal on a meter rather than getting hosed..... 

I am sure I will be back soon with my next project!! ;)
 

Offline retiredcaps

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #10 on: November 06, 2015, 09:20:13 pm »
After seeing the schematic and someone pointing out the functions of the rotary switch, I cleaned things up and slightly reformed the contact arms on the switch and we have a winner!
Similar to modemhead's blog

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

Offline copper

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #11 on: August 03, 2017, 03:08:13 pm »
I don't know much about this meter, it's too complicated for me.  :P

I had simmilar problem with my 867B and it was caused by dirt on contacts of range selecion knob.
I have just cleaned everything with isopropyl.

Function selection is done by the PTF (black stuff) switch contacts on the back side. Switch position is encoded by a voltage level from a divider type arrangement.  Maybe something is wrong with the contacts or resistors in the chain?  If you can locate TP22, you should be able to see if it's working correctly.

Edit: added schematic clip

Dear ModemHead and everyone,

does any of you know how to get the schematics of the 867 or 863?  I have an old one that had the same symptoms and managed to fix it by cleaning :)

But now I have discovered a second issue: it fails to measure DC V.  I have no idea where to start looking.
 

Offline retiredcaps

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #12 on: August 03, 2017, 05:26:53 pm »
does any of you know how to get the schematics of the 867 or 863?
I answered that almost 2 years ago in this thread.

Quote
But now I have discovered a second issue: it fails to measure DC V.  I have no idea where to start looking.
Q1. What does the meter show if you short the probes and meter is set to DCV?
Q2. What does the meter show if you measure a 1.5V AA cell and meter is set to DCV?
Q3. What does the meter show if you measure a 9V battery and meter is set to DCV?
 
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Offline subtropicus

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #13 on: March 14, 2019, 05:16:59 am »
Yesterday I turned on my Fluke 865 (purchased new in 1995) and noticed all kinds of weirdness when selecting different measurement types with the rotary switch. E.G. Vac and Vdc were blank, Set Up and Component Test were blank, and Logic showed the Set Up page. After contacting Celemetrix (Australian repair agent) and being told that it would cost $195 for a repair quote, I googled and found this thread. After cleaning the contacts of the switch with alcohol as suggested it's all back to normal! So I want to say thanks for the advice... you've saved me a considerable amount of money (which I've now spent on an Owon VDS1022i)  :)

Subtropicus
 
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Offline mimmus78

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #14 on: March 14, 2019, 04:00:05 pm »
[offtopic]I'm probably sick already, as I thought "Yay, somebody trying repair 8508A", when read words "high end fluke DMM" in topic name...  :scared:
[/offtopic]

Where's hospital for volt-nuts?  :palm:
You are not alone ...

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Offline branadic

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #15 on: March 14, 2019, 05:57:51 pm »
[offtopic]I'm probably sick already, as I thought "Yay, somebody trying repair 8508A", when read words "high end fluke DMM" in topic name...  :scared:
[/offtopic]

Where's hospital for volt-nuts?  :palm:

#MeToo
Metrology Meeting 2020 is canceled. Looking forward for MM2021
 

Offline elecdonia

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Re: Repair Fluke high end DMM. Got rolled on a used one.
« Reply #16 on: March 20, 2019, 05:05:58 pm »
I have an 867B.

I didn't use it for a couple of years. (I probably have way too many DVMs?)

Recently its rotary control switch became quite flaky and intermittent.
So I will try cleaning it according the recommendations in the previous posts here.

I also plan to check the ESR of all electrolytic capacitors inside my 867B. This meter is now more than 20+ years of age. Small electrolytics manufactured in the 1990's tended to leak, dry out, and develop high ESR.

Best regards to all!

 


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