Fluke 115 repair

[BrendanDixon]

Hi All,

I wonder is you experts can assist in the repair of a fluke 115. Basically one of my technicians, complained his meter was not working and that he tried testing the meter but could not find out what was wrong with it. I asked him to put the meter back together and I would take a look at it.

I have not run much tests but the first thing I checked was that if I put the meter in resistance mode the meter shows about 6Mohm with no leads connected.

I decided to open the meter and check to protection as a start.

R1= just over 1k
RV1 = 245kohm
RV2 = OL
RV3 = 234kohm

My conclusion was that I have 2 shorted varistors. I then removed the varistors and now resistance mode shows OL. but now if I short the leads I do not get a reading, So I know there are other problems that need to be investigated.

I left one of the varistors with my technician and he has come back to me saying that he tested the varistor and it is ok at 245kohm. I told him it should be almost infinity but he is denying this saying I do not know how to test varistors.

Can you guys please advise me if he is correct and if so what is the correct method of testing.

[mzacharias]

Is one of those varistors in series with the input?

[Shock]

Tell him that they are a OL on my multimeter he must have a special one. Unless they changed parts somewhere along the line. To test them "properly" you would need to do it at high voltage and test the clamping function. I expect they all just need replacing.

Tested both a Fluke 114 and a Fluke 117 both the same result.

[retiredcaps]

My conclusion was that I have 2 shorted varistors.

Correct.

I then removed the varistors and now resistance mode shows OL. but now if I short the leads I do not get a reading, So I know there are other problems that need to be investigated.

Did you remove all 3 varistors or just the 2 bad ones.

What reading do you get for your PTC?  It should be around 1.1k ohm.

I left one of the varistors with my technician and he has come back to me saying that he tested the varistor and it is ok at 245kohm.

Its not okay at 245k ohm.

[retiredcaps]

Looking at Dave's 117 photos, there are two PTCs.  RT1 and RT2.

Also, does DCV work at all?

[BrendanDixon]

Hi All,

Have not had a chance to investigate, in the 115 there is only one PTC I did check and this sits at around 1.1K so that seems ok. I just disconnected the varistors for now and when I get back to work next week I will take a further look.

just concerned that I have highly qualified people and they are so adamant that they are correct and I do not know what I am talking about.

[BrendanDixon]

Messages from Technician

Mr Delian: Hi Brendan. I jus checked that varistor with my multimeter. It's still good.
Brendan: Are you checking with ohms? My multimeter showed around 245kohm
Mr Delian: Yep. 200k ohm is correct. If there was a problem it would be open circuit
Brendan: No it should be open circuit. Only above 910v it is supposed to start "clamping" and giving a reading.
Mr Delian: Lol .no , varistors come in different ratings. There is 24v varistors , 110 v varistor 400v etc it depends on the designs of the circuit and ratings of the protected circuit in question. It had nothing to do with 910v
Mr Delian: If it was damaged it was supposed to have went to open circuit and shorted to earth preventing high voltage into  the circuit thus protecting he circuit
Mr Delian : Closed circuit *
Mr Delian: https://ourpastimes.com/test-varistor-7675090.html
Mr Delian: This explains it all for u
Brendan: You are correct in what you are saying. It is suppossed to be high reading. Then when voltage goes passed designed threshold. The value drops and creates a short. In the case of this varistor is 910v.
Brendan: Read the article you just sent me it will explain how to test
Mr Delian: Lmao Brendan I sent it to u bec u did not how test the component. So I'm helping understand how test these components
Brendan: Turn the multimeter on and set it to read resistance times 1000 ohms. Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
Brendan: In the article
Mr Delian:  simple if there is a problem it would be short circuit if there is no problem it would be open circuit. My varistor has high resistance so it's still good. But if it had low resistance it would be damaged
Mr Delian: that's what I'm telling u my varistor does not read low therefore it's good. 200k is high....0.2 ohms is low
Brendan: 200k is a short for a multimeter that can measure up to 1000v. Compare against yongamas meter
Mr Delian: Ay Brendan
Mr Delian: Make u example...Do u know across the lines on the RTG I got around 200k ohms and that's open circuit. RTG is operating and did not trip
Mr Delian: Ay Brendan I can't belive u think 200k is close circuit
Mr Delian: Anyway on my home. I give lessons 7 to 3.30. Monday to Friday anyways enjoy ur leave 2mrw
Brendan: Mmmmm. Dont think i need them. Just looking at datasheet. Resistance should be greater than 100Mohm
Brendan: Maybe look at voltage rating of varistor and then datasheet good to learn that not all varistors are the same.
Mr Delian: I never really said all varistors are the same. I've designed circuits with varistors before u cannot just use any varistors it dependant on the circuit design of course, taking into account  factors.
Mr Delian: U need to read the data sheet properly, there's a lot of factors involved. As can be seen on this datasheet u sent, it will measure more than or equal to 100M ohms at: 1.1mA
2. Room temperature
3. Normal humidity for one or two hours.

This is all factor dependant and it measures differently at different conditions.
Mr Delian: Good to know the electrical engineering characteristics that plays role when reading datasheets

I guess I will have to get him sent for re-training

[joeqsmith]

If the front end was indeed damaged, you must work in a fairly harsh environment.  Using this meter as a professional after doing your own service , if someone is injured, I can image the lawsuits.    Especially after the attorneys read the dialog.      Why would a company take a risk like this for $150 USD or what ever the 115 now costs?     

Many people here have posted about Fluke's lifetime warranty.  Given what I have seen posted, why wouldn't you take advantage of this?    I doubt it would be covered now that you have worked on it.   

What was the person doing at the time the meter was damaged?  I tested a 115 and its one tough meter.  I am interested in hearing what took it out.   

[Shock]

The Fluke 115 has a 3 year warranty. Continual transients could have worn it out over a long period, I doubt it's covered for input abuse but it all depends on who services it. You're right on the cost though, it's done it's job and should probably just be replaced for piece of mind and retired to home use.

[joeqsmith]

I've never looked at the one I have but you are correct, three years for the 115.   I looked at that T6-600, 2 years is all.   Maybe a trend.

[Shock]

I've never looked at the one I have but you are correct, three years for the 115.   I looked at that T6-600, 2 years is all.   Maybe a trend.

It's probably based on the odds it will have tools thrown on top.

[mzacharias]

   
Many people here have posted about Fluke's lifetime warranty.  Given what I have seen posted, why wouldn't you take advantage of this?    I doubt it would be covered now that you have worked on it.   

I think it's worth a try with Fluke. I doubt they do much more than confirm a problem, then change out the board or replace the meter.

They wouldn't spend much time on it. I doubt the board would get much more than a cursory examination.

[BrendanDixon]

Hi

Correct the Fluke 115 has a 3 year warranty. The meter in question is about 6 years old. We have an electronics department tasked with electronics repairs. so these repairs would normally be done internally, each of the technicians are given a Fluke 115 and 289. They generally use the 115 out in the field. The meter is still in excellent condition, besides the meter not reading correctly. We work in an industrial environment so sometimes the electrical environment can be harsh. I am not sure what my technician tested to cause the problem.

Anyway I have already decided that in future I am not going to be purchasing the 289s and instead the 87Vs. I have just requested 2 of the 87Vs, 1 to replace the faulty meter and another for another technician I am going to employ. as this will be more cost effective and I have never seen my techs need the logging feature of the 289.

The problem in my company is that they do not like spending money on tools. and it is going to take a while for me to get the funds approved to replace the meters.

[mzacharias]

Hi

Correct the Fluke 115 has a 3 year warranty. The meter in question is about 6 years old. We have an electronics department tasked with electronics repairs. so these repairs would normally be done internally, each of the technicians are given a Fluke 115 and 289. They generally use the 115 out in the field. The meter is still in excellent condition, besides the meter not reading correctly. We work in an industrial environment so sometimes the electrical environment can be harsh. I am not sure what my technician tested to cause the problem.

Anyway I have already decided that in future I am not going to be purchasing the 289s and instead the 87Vs. I have just requested 2 of the 87Vs, 1 to replace the faulty meter and another for another technician I am going to employ. as this will be more cost effective and I have never seen my techs need the logging feature of the 289.

The problem in my company is that they do not like spending money on tools. and it is going to take a while for me to get the funds approved to replace the meters.

Excellent. Hope you can get the 87V's approved. They'll save money in the long run. Besides, they effectively have a lifetime warranty.