Fluke 77 all ohms ranges reading low 1900 ohms is reading 1865

Started by USMCPMEL, 09-08-2011 -- 09:46:38

Previous topic - Next topic
Print
Go Down Pages1 2
User actions

USMCPMEL

09-08-2011 -- 09:46:38
Amnyone know what might cause that? Checked the switch contacts they look ok. I also put in a fresh battery that did not help either.

Bryan

#1
09-08-2011 -- 12:08:06
Did you try cleaning out the connectors with a Q-tip & some alcohol or similar?  Kind of a long shot and it's not range specific but I just can't get rid of that unfortunate memory of my dispensary visit while I was in Korea.

Hawaii596

#2
09-08-2011 -- 13:33:45
If the DC volts pot is adjusted for an exact 1900 counts (1.9 VDC on 1.9 range, etc.), the next suspect for me would be contacts on the function switch.  You might try cleaning the function switch contacts, as they cause some oddities.  If when you put a good short on it, you get zero, and on DC volts you get an exact reading, and the function switch is cleaned, it has a problem.  Those are such robust DMM's, I would suspect some sort of damage.
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
Lord Kelvin (1824-1907)
from lecture to the Institute of Civil Engineers, 3 May 1883

michthai

#3
09-08-2011 -- 18:23:16
It has been a while since I've worked on one of these; but, if there is a fuse in that circuit check to make sure someone hasn't put a slow blow fuse or the wrong size in there.

Hawaii596

#4
09-09-2011 -- 06:49:35
I can't remember on the 77, but on the 87 there are only fuses for current, but not resistance.
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
Lord Kelvin (1824-1907)
from lecture to the Institute of Civil Engineers, 3 May 1883

USMCPMEL

#5
09-09-2011 -- 10:17:04
Tried all the above. Ended up replacing the resistor next to the fusible resistor. That fixed most of the problem but I am still out of tolerance on 100 ohm range and 1000 ohm range. 100 ohms is 15 ohms high 1000 ohms is 9 ohms high. All other ranges work fine and are within tolerance.

Lasario

#6
09-11-2011 -- 16:26:16
Have you checked the MOV's? I have seen these partially short and provide a parallel resistance path that skews the readings.

USMCPMEL

#7
09-13-2011 -- 09:48:08
MOV's are fine still stumped...

michthai

#8
09-15-2011 -- 20:30:53
This may sound kind of radical; but, it does work on analog meters. Just take a shorting wire and start going across the resistors in/around that circuit. When you hit one that changes the UUT reading you can then either parallel a decade box across it or lift one end and put the decade box in it's place. Putting the decade box in there gives you the opportunity to see not only what it does to the range you are looking at; but, it also allows you to check the other ranges without soldering and unsoldering components.

Hawaii596

#12
09-16-2011 -- 08:58:40
I never heard that one (and I've been in the biz 34 years).  Is that USAF lingo?
"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind."
Lord Kelvin (1824-1907)
from lecture to the Institute of Civil Engineers, 3 May 1883

metrologygeek

#13
09-16-2011 -- 10:51:18
Yup. It's the status you use to send an item to Depot repair. Or at least it was in 1982.

griff61

#14
09-16-2011 -- 12:48:28
Quote from: metrologygeek on 09-16-2011 -- 10:51:18
Yup. It's the status you use to send an item to Depot repair. Or at least it was in 1982.
Still is, in the Army anyway. Used to send it off to salvage
Sarcasm - Just one more service I offer
Print
Go Up Pages1 2
User actions