A tale of two meters

[joeqsmith]

The story begins with a post from a member about a new meter they had purchased.

Hello EEVblog,
Thought I would mention this just to let people know there out there.  I just purchased another Extech EX430 MSRP 94.99 USD from a seller on Ebay this is my second Extech EX430 I have purchased there not the best meter by any means but the build quality and supplied leads on the first on I purchased was very nice a great little meter for quick checks and field work.  The second one I recieved last week appears to either be a knock off or Extech has let the quality slip bananna jacks are terrible, switch is as cheap as I have ever seen, protective boot is hard plastic basically it is junk.  I sent a message to Extech/FLIR but have not received any info back yet.  Looking at the boards the junk version is missing some of the silkscreen info that is on the older one I have.  Has anyone else seen a drop in build  quality of Extech items?
Jason

The original post may be found at:
https://www.eevblog.com/forum/testgear/extech-build-quality/

In July of 2012 I purchased an Extech EX540 for $300.  I still use the meter often and the only problem I've had with it is when I loaned it out to someone who turned the selector past the dead stop and broke the switch.  This required some fancy epoxy work but I was able to repair it.   

I picked up a second one that has a A14 SN compared with my original A10. 

When I opened the box, everything looked good.  Then I turned the meter on.....
 

[joeqsmith]

Now keep in mind the old Extech is not a bench beauty queen.  It gets used and as such it gets dropped, things get spilled on it, it get's hooked to things that maybe it shouldn't and sometimes people turn the knob past the dead stop.....

You can see the lettering has not held up so well.   Notice that the new case is also a darker orange.  This could be from the sun but the entire case of the old meter is lighter. 

[joeqsmith]

Notice how the case has cracked on the older meter where the probes are stored.    Wait, there's a new sticker too.   

[joeqsmith]

Getting back to turning it on for the first time.  Well, as I turned the selector switch, the meter turned off.  Then it reset.  I played with it a little and the selector was really intermittent.   I had never had any problems with the old meter's switch until I loaned it out...   

But wait, does that old meter have a blueish tin to the LCD??   The new one looks more black.   

What you can't see in the picture is how the back light is flickering on the new one where the old one is nice and solid.    On the plus side, it's not singing...

[joeqsmith]

I've had my old meter apart before and was not too concerned with turning the meter for warranty.   So out comes the screw driver and as I went to remove the battery cover I noticed this small difference...   A little advertisement did not concern me too much. 

[joeqsmith]

While I was removing the screws which have a washer and an O-ring on each, I noticed one of the O-rings was missing.   I looked in the hole and somehow it had been wedged down in there.   Not a big deal.  But then I look at the cover....  Something strange.   There is a spring on the PCB that would normally attach to a shield but there is no shield.

[joeqsmith]

Maybe it was left off by mistake.  Maybe it was a design change.  I wrote Extech and asked.   In the mean time, I broke out some copper foil.   

[joeqsmith]

To be honest, the missing shield was not the first thing I noticed.  What I noticed first was how the metal shield that covers the sensitive area looked like it had been forged with a rubber mallet.     The old meter is bent nice and cleanly.   

You may also note some of the other differences.  The old PCB has a deep gold tin to it compared to the new.   At least they cleaned up that botched part.

[joeqsmith]

Where was I going with this, oh yea, the meter does not turn on..  I was also seeing strange things like the meter would not read the correct resistance.  Let's see what's going on with that switch. 

Sorry for the poor quality picture.  There are six contacts, five of which are the same. One is wider than the others, shown on the right.   It's resting height is much lower than the others.   I took out my trusty X-acto and shaved a very small amount off the ends of the plastic so it's resting height was the same as the others.  I also removed any burs I saw and made sure none of the contacts were hanging up.   

Looking at the rest of the plastic, I was reminded just how weak this area is.   IMO, this is a very poor design.  On the old meter, the hex insert split and half broke off.  I found an inverted star washer that press fit over the shaft, then epoxied the whole thing up.    Sanded the plastic first (learned from the first switch).   If this breaks, it's taking the shaft on the switch with it!

[joeqsmith]

So the switch is all apart and I am playing with the old meter while I wait for the epoxy to dry.   I was thinking for a water sealed setup, this really has a nice feel to it.   I pick of the new meter and turn it.  Keep in mind there is no switch.  It's tight.  REALLY tight!!!   So I decide to take the dial off of the new meter to see what's going on.   I look at the C-clip and rather than fitting into the grove it is smashed around the shaft. 

I spent some time with the Dremel next grinding that C-clip to about 1/3 of it's thickness.  I then honed the flat side and rounded the edges.  Yes, finding a better C-clip may have been an option as well....   I cleaned all the parts up and greased them.  The clip fits as it should now and the dial is much smoother.   Snug, but smooth....

The end of the clip did not fit inside the groove before.  It was bad.

[joeqsmith]

Crazy EX540 with your 6 MOVs, 3 PTCs and 3 HV resistors.  Where do you fit all this stuff?    Quick answer, you don't....

The workmanship in this area was poor.  Clearance, we don't need no stinking clearance!  The leads on one PTC were really close to an area that they should not be near..  Extech, you want these meters to survive don't you?

Solder, bend, heat shrink....   

The one thing I never liked about this meter was that ground return.  All the current flowing in that massive loop.  The MOV's return path is so close, yet so far away...... 

[joeqsmith]

The PCB appears to be a few revisions newer.   Note the diode near the - battery connection on the older meter.   

[joeqsmith]

How much does a star washer cost anyway??   The new meter was missing the two washers for the common and uA/mA studs.  These were there on the older version. 

[janoc]

I have an Extech 470 which has also similar problems - the range switch is intermittent, the meter often shows random nonsense on the LCD or just locks up. The original seller has actually sent me another 470 free of charge, which was working.

You will find quite a few posts on the forum that Extech has quality control problems, some meter series are good and some are just junk, even for the same models. They are probably changing factories where the meters are assembled or something. I have sold my working 470 recently and not planning to get another Extech. Not worth the money, IMHO. You can get a much better Brymen meter for that price.

[AF6LJ]

Wooo
Not Good, I have to wonder if that is one of those non authorized (midnight manufacturing CO) meters.

[Lightages]

This is what most people complain about with the Extech meters made by CEM. The quality is all over the place..

[joeqsmith]

Extech supplied the alignment procedure for the meter and I verified it.   They do not have adjustments for the DCA, capacitance or resistance.  The meter is well within spec but the DCA could be a little tighter IMO. 

So the switch works very well now.  Not real happy with the flicker but it's tolerable.   

Attached 1mV and 10V with the two EX540s compared with the BM869s and UT181A.   

[joeqsmith]

Missed a couple.  Note the flat vs round shunt.  White glob on xtal vs solder.  Axial resistor under fuse.   I also cleaned up the soldering (shunt, fuse holders, protection.....) and cut off the excess leads.   Wonder how they crushed that can.  At least they are still using SIBA fuses.   

I do like the meter overall but the $300 price tag, I expect it to be much higher quality.   It does have an RF link and it actually works.  You can talk to the meter with Labview.   Personally, of all the meters I have looked at I still like the BM869s best for a portable bench meter. 

[joeqsmith]

You should have a look at the contacts.  Maybe a little trimming with a razor blade would solve it.   This one is now rock solid.

It was really strange how it acted.  The meter would turn off at times.  Or it would change modes, which I assume was a reset.   In ohms, it would read a short as 0, but it would read 50 ohms as 0.  1K as 0.  10M would read 10M, most of the time.   Cap mode was the same except it would reset at times bask to ohms.   Brand new, seems like it would never have made it out of the factory.   

I have an Extech 470 which has also similar problems - the range switch is intermittent, the meter often shows random nonsense on the LCD or just locks up. The original seller has actually sent me another 470 free of charge, which was working.

[janoc]

You should have a look at the contacts.  Maybe a little trimming with a razor blade would solve it.   This one is now rock solid.

I had it open a few times already, the switch looks ok visually, so not sure what the deal is. I will try to check it again, thanks for the tip.

[joeqsmith]

I did hear back from Extech who offered to repair the meter.   I will say I have been very pleased with their communications.   I provided them with a link to this thread.   

I almost forgot...  I had not played around with the back light a whole lot after going over the meter.   I was planning to make a video with the high speed camera showing the flicker.  Looking at it very carefully I can no longer see any sort of flicker.  I suspect this was also caused by the intermittent selector switch.  It makes sense as the power would shut down.   

[jitter]

Thanks for this comparison and the solutions, it may benefit others out here that have these meters.
I would concur with you that the little differences between the old and the new meter you're describing are indeed the result of revision changes. Changes to fix oversights.
The bigger issues, mainly the mechanical misfits, seem to me to be more like the result of changing suppliers.

I've been working on a metrology grade instrument for over 10 years now, and at first we assembled everything in house. By now most modules have been outsourced to a plant the company I work for owns in Eastern Europe. They have very good quality control but when they had just started making them I saw all the little things we did wrong at first reoccur, until they learned about them too.
Hopefully, with your Extech it's a similar thing and they get QC in place again, or otherwise it doesn't bode well for them.

I have an EX830 that I posted a teardown of only yesterday. Based on what I found I had already decided that the chance of me buying another Extech was rather slim, and your thread reinforced that feeling.

One thing that also plays a role is the price. This meter cost me € 160 in 2007. It's still available now, but today they want about € 250 for it...
Perhaps at the time the brand was new over here and they were selling it under the market value to get a foothold.

[joeqsmith]

Possible. 

When my wife saw it the first thing she said is it looked like a used meter that someone had attempted to repair it and resold as new.   That's also possible.  Maybe it was a demo unit, which could explain the bent metal can and missing washers.   We could make up all sorts of stories but really I have no way of knowing.   

There are only a couple of video reviews of this meter.  This one shows how to measure the temperature of your AC line. 
https://youtu.be/lFkgyQEq_Jo?t=62

This one shows how the metal can may have been bent.
https://youtu.be/zJpqbkoOGgE?t=84

I thought about doing one but with so many mods to the meter, I suspect it would bias the results.   

I would concur with you that the little differences between the old and the new meter you're describing are indeed the result of revision changes. Changes to fix oversights.
The bigger issues, mainly the mechanical misfits, seem to me to be more like the result of changing suppliers.

[jitter]

Possible. 

When my wife saw it the first thing she said is it looked like a used meter that someone had attempted to repair it and resold as new.   That's also possible.  Maybe it was a demo unit, which could explain the bent metal can and missing washers.   We could make up all sorts of stories but really I have no way of knowing.   

Your first EX540 has revision 5 on the pcb and your second is already up to 9.
To me it seems most likely that the "bodges" that were put on the "5" to solve some issues found their way into the layout of the subsequent versions.
I say this because my work is mostly on that instrument I wrote about in my previous post. It's a bit of a niche instrument, so you're talking about 500 a year, worldwide.
With those low numbers, some "bodges" (fixes) may remain in the design quite long as redesigning and respinning boards just isn't cost effective. Often they wait until a number of mods can be put in the redesign all at once.
And if the mod is considered of high priority, we still get to modify and use up existing stock which may be 100, 200 boards tops.

This Extech would no doubt sell more, so they just use up old stock, modify them and then redesign the boards with a newer version for the next batch.

There are only a couple of video reviews of this meter.  This one shows how to measure the temperature of your AC line. 
https://youtu.be/lFkgyQEq_Jo?t=62

That guy looks like he poked his own fingers in an outlet one time too often  .

This one shows how the metal can may have been bent.
https://youtu.be/zJpqbkoOGgE?t=84

Maybe they did that to your first meter, buffed it up and sold it to you ("like a bought one" Dave would say). 

[joeqsmith]

Let's assume there were 5 revisions, or 4 after my original meter.   Now lets look at what changed with the PCB.   The plating.  There's one rev.   That gives us three revs to fix the tacked on diode bodge.   

I'm sure there were other changes.

Your first EX540 has revision 5 on the pcb and your second is already up to 9.
To me it seems most likely that the "bodges" that were put on the "5" to solve some issues found their way into the layout of the subsequent versions.