Fluke Model 76 True RMS multimeter, parts identification, etc

[JeffS]

Ok, So I spent 2 hours trying to find a .pdf of the SERVICE manual for this and found about 100 other fluke service manuals, but none for this.

Here's what I know, a "friend" tried to use my meter to measure the output of a neon light transformer and smoked my meter. The input section appears to be protected by two resistors which I need help identifying. I bypassed the resistors and the meter appeared to get proper readings from the limited testing I did. As such, I think starting with these would be best and go from there.

One of the parts, as listed in my USERS manual, is a:
"RES, MF, 450 , +-10%, 100PPM, FLMPRF, FUS"
which I assume to mean a:
Resistor, Metal Film, 450 ohm, +- 10%, what is 100 PPM????, Flame Proof, Fusible

So what is 100 PPM, where / how can I figure the watt rating and any idea where I can order more?

But I'm not sure which circled component is which??? Is that the one on top or bottom of the photo?

As far as a physical description of the two devices, the item circled on the top looks like a resistor, has one yellow band and one blue band, is about .5" long and 3/16" wide.

The other parts from the best I can tell, it's also a resistor or maybe some type of protection diode?
what it says on it is (from what I can read on it):
IRC or 1RC
"1M00 1%" or "IM00 1%" or "IMoo 1%"
GS-3 TO
4448 or 444B
"1M00 1%" or "IM00 1%" or "IMoo 1%"

so what is this part? I googled a few tries but didn't see anything that stood out. 1M resistor? I need to figure out the exact details for both of them. I have attached photos, including a dime for size identification (they are about .5" long)

which is which??

Thanks!

 

[davenn]

100PPM = would normally be read as 100 parts per million
tho I have never personally seen a resistor labelled as such. thats usually more often seen on a RFoscillator when describing its stability.

1M00 1% I would take as a resistor that is 1.00M Ohm (1 million Ohms) and 1% tolerance

the part with the 2 coloured bands dunno maybe a Hi Voltage arrestor not sure put an Ohm meter across it does it have a resistance reading or is it open cct maybe its a enclosed sparkgap, which wouldnt be uncommon on the input to a multimeter

Dave

 

[JeffS]

Ok, found a little more:

I think the item on the bottom of the photo could be replaced by this:
http://www.mouser.com/ProductDetail...=sGAEpiMZZMtlubZbdhIBINKdDf4T33FqkxkWsXCdJl8=

with this datasheet:
http://www.irctt.com/file.aspx?product_id=36&file_type=datasheet

which seems to be a current model of what's in there. I think the original was a 1% item and this is 5%, but other than that appears to be the same? Agree?

 

[JeffS]

Ok, measurements:

The part on the bottom that is labeled 1M 1%, reads at 70k ohm, which I'm taking as it's bad.

The part on the top of the photo with the blue and yellow band doesn't read on my other meter, just shows OL, so no help there at all.

thoughts?

 

[davenn]

Hey Jeff

that data sheet was very informative huh so the 100PPM is a temperature coefficient. didnt know they produced resistors with temp co-effic's we learn every day

Now I assume it was reading 70k Ohms when out of cct ? ... if that when in cct, you could be see the effect of other components around it
70k instead of 1M is definately not good

ok well that 2 banded device being open cct is sorta helpful as it goes to back up my enclosed spark gap discharge type of device
( it could still possibly be an open cct (faulty) some sort of other component)

You see how that the circuit board is "cut out" around that right hand input, that infers that its a hi voltage or hi current measurement input, you would be able to confirm that
one side of that 2 banded device goes to that input where does the other side go to ? there must be a track on the other side of the board that cant be seen. maybe put up a pic of the other side in that area


Dave

 

[davenn]

oookkkk

you "forced" encouraged me to open up my trusty ol' Fluke 87 meter. its a good 20 yrs old
and still going !!

I have one of those large brown resistors and a 2 band component coming off the
volts input socket (1000V max)

the resistor has 909k 1% and yes it is 909 k Ohms
the 2 band device has a green and a blue band in cct its measuring 1 k Ohm
that appears to be a correct value
I do see a sparkgap component in that area its a yellow item, looks like a ceramic dipped capacitor, I can see a slit cut into it.

cheers
Dave

 

[Militoy]

The 2-band device looks kind of like a molded inductor - though i've never seen one with less than 3 color bands. I'm not sure if we still have any Fluke 87s around, to put an LCR bridge onto.

 

[davenn]

The 2-band device looks kind of like a molded inductor - though i've never seen one with less than 3 color bands. I'm not sure if we still have any Fluke 87s around, to put an LCR bridge onto.

I wouldnt expect an inductor to have a 1k Ohm resistance unless faulty and I know my one isnt faulty 99.99% of small inductors would have a resistance of less than a couple of Ohms (excluding transformers, large chokes etc)

cheers
Dave

 

[JeffS]

Ok, so I replaced those two parts and it's all good. I'll post the parts I used in case anyone finds this through a search in the future and is in need of answers.

The part that is labled "IRC", etc is a Metal Film Resistors - Through Hole 3WATT 1MOHM 5%
it is available from Mouser for like $0.51
Mouser Part #: 66-GS31001004JLF
Manufacturer Part #: GS3-100-1004-JLF
This part is soldered onto the board right above the tan part circled in the photo.

The tan part w/ the single blue and yellow stripe is a:
Resistor, Metal Film, 450 ohm, 10%, Flame Proof, Fusible
Manufacturer Part #: 107398 (also known by other part numbers in the owners manual but I don't have my manual handy at the moment)
I found it by searching for "Fluke 107398 Resistor"
I purchased it from a placed called Ucite.com for $4.80

Put both parts in tested all the functions and it works great!

 

[davenn]

ohhh didnt realise you posted so many days ago
hopefully you will still visit the forum regularly

outstanding on the repair and the info re the parts

cheers
Dave