Mastech MS8229 continuity test fail (brand new)

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
Hi, I've just received a Mastech MS 8229 mutlimeter and I am so happy about it, cause so far I've been using this yellow cheap mini multimeter:



It still works, but I've repaired the black lead cause one day, PLOFFF!, the cable fell apart, hahaha. I had to solder the broken cable directly to the end of the lead (the pin/spike), hahaha. But you know, for a beginner it's OK and useful.

After 2 years using that cheap thing, I wanted a new better one, and I found the Mastech MS 8229 to be the perfect upgrade, and I've read pretty good reviews about it. So I read the instructions, put the new batteries and do a simple test of continuity with the leads themselves. What I find is that the ohm is all over the place, jumping from 10 ohm to 200 ohm or even OL (overload), the pitch sound continuously getting interrupted. This is a quick video I've made comparing both of them:

https://streamable.com/d2vee


This is not how a multimeter of this quality should work, right?
What could it be?

I mean, I know it's not a FLUKE, but even the chinnese cheap thing is way better at that simple test.

I've checked the leads and yeah, they are correctly inserted, besides the multimeter has lights in each hole that turn on if there's no connection. I've even checked with other leads, same result. I've already contacted to the seller, by the way.
 

tcmtech

Joined Nov 4, 2013
2,867
Wiggle the dial while doing the test and see what happens. Fair chance its got a weak connection on the contacts for that part of the circuit due to excessive dielectric grease from when it was made.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
Thank you.

A $50 multimeter should mark steady and constant 0-4 ohm in this test, even when rubbing the leads, as well as a constant pitch, right?

My yellow cheap chinese multimeter beeps constantly even when rubbing the leads, although it marks from 3 to 25 ohm, probably due to its poor quality. But I expect a Mastech MS8229 to behave as I've just previously described.

This is a really basic tool, so essential in my reparations, and if the MS8229 works like this, first I don't know how the rest of the functions can be any better,and second I'm definitely returning it and buying another DMM.
 

Tonyr1084

Joined Sep 24, 2015
7,943
I'm thinking you mean when reading ohms with the leads dead shorted you're not seeing 25 ohms but maybe 0.25 ohms, or maybe 2.5 ohms. That has been my experience with just about every DVM I've used. There's almost always some test lead resistance and some meters allow you to zero out the reading in order to negate the line lead resistance.

You're right, rubbing the leads together as you did with both meters should produce the same desirable result. You even stated you tried different test leads and got the same result. I stand on my earlier comment, time to get a warranty replacement - or your money back and try a different brand.
 

ErnieM

Joined Apr 24, 2011
8,377
Are you using the leads you repaired? Can they be broken again?

Try using just ONE lead, probing back into the contact where the other lead was removed from. Repeat with the other lead. Heck, repeat with a good piece of uninsulated wire into both holes.

See if the problem follows a lead or is always there inside the meter.

Then if it is still in the meter, check the battery. Worn batteries can yield very weird measurements.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
I try to explain everything as precisely as I can, but I see it's an impossible task, hahaha. To answer some questions:

1. The digital multimeter is brand new, and so are its accessories.

2. Yes, I've tried different leads, all of them working fine, tried also different batteries, all of them correctly charged.

Now I explain the lead reparation: the cheap yellow chinese multimeter is the one that has one lead broken, the black one. I've repaired it by soldering the cable directly on the lead end, kind of a botched job, but it works. Now, even under this condition, the cheap multimeter is still responsive in the continuity test, the beep does not stop at all even when rubbing the ends, it works just fine, and I expect that my new $50 multimeter reacts even quicker and more responsive, which is not the case at all, indeed it's the opposite.

The cheap chinese multimeter works fine in the continuity test, it beeps whenever the leads are touching themselves, doesn't matter if I'm moving them or not. Nevertheless, the screen shows from 25 ohm to 4 ohm, and I think this is due to its poor quality. I expect a $50 multimeter to show steady 0 to 1 ohm of resistance (more like 0 ohm, but I know this depends on the model). The Mastech beeps randomly and it shows a resistance of 4 ohm, then jumps to 20, then to 400, then OL, then back to 30, etc... you can see it in the video, it's crazy. I've already contacted the seller, that subject is fixed and closed, he was so nice.

Now I'm trying to solve this continuity test failure instead of looking for another product, to see if I can easily repair it or not. What kind of troubleshoot should I do?

I'm pretty sure it's a inner problem, since the leads look professional and are in perfect condition. Besides, I tested another pair of leads and the same error occurs.

Thank you. I can do a video making all kind of tests: see how good the ohm meter works, etc...
 

Tonyr1084

Joined Sep 24, 2015
7,943
Here's my bottom line: You have a new meter that is not working properly. Don't ruin your chances for a refund or replacement by opening it up and trying to FIX what should not need fixing. Yes, I agree, it sounds like you've done all the right testing and for whatever reason the meter just won't work no matter what you do externally with all user interface points. However, if you open it up chances go out the window for the company to honor a warranty replacement. So I'd advise you don't. If it were an old meter I'd say go ahead and give it a shot. But since it works dodgy no matter WHAT you do - the problem is clear - it's an internal issue. Don't fix it - send it back and get your money back. Buy something a little better known. Remember, high dollar doesn't always mean high reliability. I can sell crap for 10¢ a pound and nobody will buy it. But if I advertise it for $1,000.oo I bet someone would buy it thinking it must be quality crap.
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
I've already contacted the seller, that subject is fixed and closed, he was so nice.
Sorry Tonyr, you misunderstood that sentence. By that I meant that I've already been in the store and have talked to the seller, so don't worry about it, thanks.

Now I'm trying to fix it, but I don't know where to start, I mean, may be some of you have a better idea of what to do to troubleshoot this.
 

Tonyr1084

Joined Sep 24, 2015
7,943
So the seller didn't give you a replacement? What about contacting the manufacture?

If you have no hope of returning it or getting a replacement then go ahead and open it up. But ONLY if you can't return the one you're complaining about. I'd suspect there may be a cold solder joint inside the DMM. Possibly (often) at the banana jack where it plugs into the meter. Leads can put a lot of stress on the joints, and if the meter was handled rough during shipping the problem might be right at that solder joint (or those solder joints). If not then check the entire board for cold or fractured solder joints if you're capable of doing that. Whatever you do - don't start reflowing everything. Chances are good you can cause a solder bridge (short circuit)(by the way, not likely the problem now) or you can over-temp a component.

These things (SMD) go through an oven designed to heat the entire board and cause the solder paste to melt and flow, and thus, make the solder joint. A lot of engineering has gone into the necessary heat and the time in the oven as well as the cool down period. Hand soldering components can yield good results if you know what you're doing. Many people can't handle soldering SMD's. I'm experienced, and even I struggle with it. I'd rather not if I don't have to.

If there is a solder joint failure it's most likely going to be right at the leads. But because the DMM is not in my hands I can't tell you for sure where the problem is going to be. It COULD be component level, meaning you could have a bad component.

I wish you well. Just don't burn anything with the solder iron. Remember, when you heat one side of an SMD it expands. When it cools it contracts. If the solder does not move evenly and equally on both sides you can put a lot of stress on one (or both) joints OR on the component itself.

Personally I still think you should get your money back. At the very least a replacement.
 

tcmtech

Joined Nov 4, 2013
2,867
TO me your whole video looks like what happens when the lead pins are not getting solid contact. It appears you're barely touching them together rather than firmly holding them together.

I also have a Mastech meter, an MS8265, that will do the exact same thing if the leads are not making solid contact with each other.

Unlike the cheap low end meters Mastech have pretty fast circuit responses and thus will pick up on the slightest variances in continuity that the cheap meters won't so by my meters action yours is doing exactly what it is designed to do. Give you a very fast audible reference to the circuits continuity ans since you do not have a solid contact is telling you that with the beeper function. ;)
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
I'll post some nice pictures here of the inner parts so you can clearly see all the circuit. Unless I clearly see a very bad solder joint, I'm not using my soldering iron to repair this or re-do solder joints. Since this is the very first test I did and failed to pass it, I have almost not used the multimeter. Tomorrow I'll check its other functions to see if they work as good as I expect from a $50 multimeter.

One thing is clear, if it fails due to a contact problem between the leads and the IC, then almost every other function should behave the same way, faulty. My guess is that it will fail at the continuity test but it will do the rest of the functions alright. In this case I (or we) should focus on the specific components and solder joints that come into play when the continuity test function is selected. Unfortunately the continuity test is a thing I use every day in all my little reparations and right now I'd rather use the yellow cheapo than the MS8229, and I don't want to feel like that at all, hahaha, I want to upgrade that yellow submarine.

P.D: I'll make a better and a little bit longer video showing how the cheap yellow multimeter is way better and more responsive than the MS8229. Tcmtech, the contact between the leads, showed in the video, in both multimeters, is rock solid. I'm not trying to make the MS8229 fail, hahaha, that would be ridiculous. As I've already said, this is the first thing I did to test my new acquirement and I did it the same way I do it with my yellow multimeter. Besides, it's not possible to make it fail like this at purpose, you should be moving your hands incredibly fast to emulate that beep sequence with that much interruptions. I've seen videos of different Fluke multimeters and they all behave like my yellow multimeter, but more responsive, almost instant beeping even when touching the leads for a few milliseconds. That's kind of what I was expecting to see.

Thank you, I'll come back with pictures and a new video.
 

tcmtech

Joined Nov 4, 2013
2,867
Tcmtech, the contact between the leads, showed in the video, in both multimeters, is rock solid.
You weren't pinching with with your fingers so I have doubts. Especially so given I can replicate the exact same beeping and erratic ohms readings effects with three of my meters doing things the way you did just touching them together.

I have three different brands which all do the exact same thing as yours plus a number of cheap Harbor freight and such off brand generic units like yours that do not. In fact, when I swapped the lead sets around from one meter to the other they all had these associated responses. The cheap ones could care less about a scratchy connection and the higher quality one all picked it up without hesitation.

To be honest when doing continuity and low resistance testing you want something that has such a fast response it can pick up a weak contact or loose connection issues and not pass over it like nothing's wrong.

Which given that I say nothing is wrong with your meter and it is working exactly as a higher quality meter should work by picking up the details that the cheap meters miss. ;)
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
Wow, wait, I need time to digest this, hahaha, since now scratchy beeps when the leads are clearly touching constantly is a sign of high quality. I can guarantee you that in the video the leads were touching perfectly fine, just like I would test any connection. I had to hold the camera while shooting the video, but I've also of course done what I did in the video with 2 hands, one lead in each one, joining both leads "the right way" AKA pinching with my fingers.

OK, wait for my video where I'll put some tests and tell me what you think.

Thanks for passing by!
 

tcmtech

Joined Nov 4, 2013
2,867
Wow, wait, I need time to digest this, hahaha, since now scratchy beeps when the leads are clearly touching constantly is a sign of high quality.
Its a sign that higher quality meters use different circuit designs with far more range and sensitivity in their testing capabilities than the cheap ones use. Hence the reason they cost more.

My cheap meters have a good 1/4 second or better time lag between when the leads touch and when the beep starts and about the same when thy disconnect before the beep stops. In electrical circuit testing a lot can happen or be missed in a 1/4 of a second!

Same concept of looking at waveforms with a $250 10 MHz bandwidth oscilloscope and a a $1500 100 MHz one.
If you were using the 10 MHz scope to look at a waveform that showed one thing then switched to the 100 MHz scope and started seeing a whole lot more detail and noise on the signal the cheaper one didn't show would you assume the 100 MHz scope was bad or that just maybe there's a reason it cost 6 times as much and that just maybe it's able to show you things the cheaper unit couldn't?
 

Tonyr1084

Joined Sep 24, 2015
7,943
Build your own test lead - banana plug on each end of a wire and plug it in. If the connections are good and the plugs are making good contact and your meter still does the intermittent response then the meter has problems. But if it stays constant then try wiggling the wire around. If things change while wiggling the wires then there's a problem with the meter.

Few years ago I did a short job assignment at a factory that made Custom Immersion Heaters (electric). The lead inspector was testing JK thermocouples and was rejecting a large portion of them because of intermittent connections. As I observed the process she was wiggling the test leads around quite a bit in an effort to see if the unit under test was faulty. I quickly became suspicious that her meter was defective. So I asked if I could see the meter. I pinched the test leads together as TCMTech suggests and the meter seemed good. So I began moving the leads around and quickly discovered it was the meter that was failing, not the units being tested.

She tried to defend her position by insisting that the meter was within calibration dates and that it was to be 100% trusted. She got very angry when I insisted she take it to the calibration lab. So angry that she insisted I leave her area. So I spoke to her boss. He wanted to believe her over me - someone with over 30 years quality control experience in the electronics field, and a good deal of that experience had to do with calibration. Wasn't until I spoke up at a board meeting, being the "On Site Quality Inspector" for their customer that they pulled the meter in for testing. The problem ? ? ? Bad solder joint where the leads plugged in. All those units she rejected were probably just fine. The good news is that nothing bad got past. Bad news is that a lot of good product went in the scrap bin as well.

Moral of the story: Make certain your unit is stable under all conditions. When testing your unit you should make the jumper as described and plug it in. The meter should ring steady and show near zero ohms. Wiggle the wire about fairly vigorously, but not so vigorous to cause damage. If the meter falters at all then double check your jumper. If you're confident your jumper is well made and the meter still responds sporadically when wiggled then you have a bad meter. Be it solder joint or faulty components internally.
 

MrAl

Joined Jun 17, 2014
11,559
Hi,

Another possibility could be due to the type of banana plugs used. They are not all the same.
Some banana plugs are longer, and some have a plastic shielding and are longer.
You have to have the right type to get it to work right.

You can try the paper clip shorting idea, that sounds good.

There are some banana plugs with plastic shields that activate a contact inside the meter. If you have that type you'll have to make darn sure you have the right leads or nothing will work including the paper clip test.

I dont see why you just did not get a replacement. Could it be that the guy gave you a partial refund and you keep the not-so-good meter and you agreed to that?
 

Thread Starter

rambomhtri

Joined Nov 9, 2015
574
Thank you very much.

Besides all the tests I am planning to do to compare both of them, and all the pictures I am going to take so you can see the MS8229 better, I'm gonna test too all your ideas.

So, one is take a bare paper clip (or a copper cable better?), introduce it into the 2 holes and that should make a constant beep. I find this idea good to make sure the resistance is 0 ohm aprox., but I'm not sure how can I make the contact between the hole and the paper clip solid. I'm gonna check with my yellow multimeter both leads of the MS8229 and show it, but as I said they look awesome and in perfect condition. Also, the holes are activated by the leads in the MS8229, there are like spring buttons that deactivate the holes, and when you introduce the leads into the holes that moves one thing and the connection is correct. You'll see that in the pictures.

I see also that a lot of people are questioning the leads. Please, notice the Mastech MS8229 comes with a pair of leads with the MASTECH brand on them, plus a K thermocouple. I mean, I know they can be faulty, but definitely that it's not due to incompatibility between components, as I've seen some have suggested.

Gimme a little time to take the pictures and shoot the video, I'm kind of busy right now and I want to do it properly.

Tonyr that was an interesting story, can you explain a little bit more about how did it go. You were walking around and noticed that an employee was tossing a lot of units, and you saw what she was doing and you thought about what if the multimeter was wrong.

Why she did not believe you?
I mean, I know experts normally don't take other people's advice easily as they tend to think they are doing it right (which is almost always true cause they are experts), but it was as easy as taking both leads join them, right?

Then what happened to make them take your suggestion seriously?
 
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