Extech EX830 AC/DC Clamp meter teardown

[jitter]

I thought I'd have a look inside my Extech EX830 True RMS AC/DC clamp meter as that was still on my to-do list.
I bought this meter in November 2007 for  €160, but never tore it down, until now. Edit: wow, I had to double check that I really paid € 160 for it as it seems to be sold for € 240-260 nowadays!

For that money, it came with testleads (obviously), a K-type thermal sensor+adapter and a pouch.

The case feels a bit flimsy and it creaks and flexes when you squeeze it. Screws for the case are self-tappers, the battery compartment lid is held on by a screw in a threaded insert. The battery lid is difficult to remove as it won't pop out and you need to use your finger nails to try and pry it out. Careful with the screw, it's not captive.

The range switch doesn't feel all that nice to operate, despite having ball bearings on springs to lock it into place. When the auto power off kicks in, you must rotate it to the off position first, unlike a Fluke it won't wake up by pressing a button.

This meter can be considered a fully fledged DMM which measures current with a clamp instead of through a shunt. So if you don't need to measure down into the mA or uA ranges, no additional DMM would be required. A useful extra that has seen more use than any other measuring range is the built in IR thermometer with laser.

The inside looks OK, but I can't say I'm impressed with the quality of finish. The designer/manufacturer is "TOPMAN Industrial".

[jitter]

If this meter needed adjustment, it would not be a closed-case procedure, lots of tiny pots are strewn across the pcbs...

[jitter]

The top pcb is fixed with two screws on threaded standoffs. The bottom reveals circuitry that's gunked over with black stuff... Why did they do that? To prevent reading the markings? I can't think of any other reason...

[jitter]

Some more miscellaneous photos...

[jitter]

And I hear you asking about the money-shot... Unfortunately, it looks like the chipset is right under the LCD, and I won't disconnect a zebra strip unless I absolutely have to. Also, no peeking inside the clamp, it's plastic shells are glued together.

[joeqsmith]

The leads some how get all the way to the back of the board to the PTC, then all the way back to the front of the board with Q6-9?   If you don't mind, please trace out the front end of that thing. 

[jitter]

It's back together again, and unfortunately I'm not going to open it again, I don't like my chances with the self tappers of this meter. Of just three total one is already on the way out.

I did take one photo of the whole of the other side of the board, unfortunately part of the trace is hidden beneath the LCD.

[Psi]

I have the EX730. I've not opened it up but it does everything i want in a clamp meter.
AC/DC/true rms and 40A to 800A ranges.
No complaints other than needing to zero it every time.

[jitter]

I have the EX730. I've not opened it up but it does everything i want in a clamp meter.
AC/DC/true rms and 40A to 800A ranges.
No complaints other than needing to zero it every time.

Apart from the irritating creaking every time I pick up the meter (it doesn't take much at all) it has worked fine for me too.

I don't think the zeroing of the amp range is a fault. I need to do it on this one too every time and my old Voltcraft I blew up one day was no different. So perhaps it's inherent to clamp meters.

[joeqsmith]

Yes, for most DC clamp meters you need to null the offset. 

I don't think the zeroing of the amp range is a fault. I need to do it on this one too every time and my old Voltcraft I blew up one day was no different. So perhaps it's inherent to clamp meters.

[barbucha]

Hi i wanna ask a question about ex830. I have one too and trying to repair it. I need to know whats name of parts on picture number 7. i mean two transistors which are under themself and have socket89. and btw its not bga6289 i try it thx for answer.

[jitter]

Please be more specific, like e.g. what are their reference designators?
The way I'm interpreting it now is that maybe you mean U2 and U21?

Please be aware that I don't know of all the components what they are, so I may not be able to tell you.

[mos6502]

Thanks for taking the effort  Considering the price is over 200 bucks, it's disappointing. Low quality PCBs and low quality plastics (looks like cheap ABS, that's why your screw got stripped).

[PedroDaGr8]

Thanks for taking the effort  Considering the price is over 200 bucks, it's disappointing. Low quality PCBs and low quality plastics (looks like cheap ABS, that's why your screw got stripped).

That is pretty much Extech in a nutshell.

[joeqsmith]

I like my EX540 that I use for work.  Not near as nice as the Brymen but alright.  But the one I bought brand new to benchmark was dead right out of the box and had various quality problems, not to mention what appears to be a supplier problem with the RMS converter they are now using.  People who claim CEM is hit and miss are right.     

With all the low end, bottom of the barrel meters I have looked at, I have yet to jack up a self tapping screw.  I suspect many people don't know to turn the screws backwards until they drop into the original threads, or they over tighten them.

[barbucha]

Sorry i forgot to write their position and you are correct, its a U21 and u 2, I know that you maybe not know this but im trying it And i am grateful for any kind of clue

[jitter]

Take a look at the eighth photo, you can read the code on U2 and U21. It reads "3A0X" or "3AOX".

I don't know what these are, but the refdes starts with "U", so I'd guess it's an IC (e.g. a voltage regulator), and not a transistor.

The case is a SOT89-3.

I'm not at home right now, so I would suggest you try to find the code in one of the online SMD codebooks.

Good luck!

[barbucha]

I tried to find it by smd code. It says it´s BGA 6289, i baught it but after place and solder on its position it doesnt working perfectly. It shows random value on all ranges, backlight desnt work, And laser from thermometer doesnt work, when i give 1original U2 back backlight working and laser from thermometer lights too, I know that U21 is the only one broken part. But dont know what is it ^^

[jitter]

Back home and applied some google-fu...
SMD-codes can be tricky and most codebooks aren't nearly complete. If they don't help you have to turn to the datasheets from the manufacturers. But that means knowing "who" and "what" first.
Thanks to AliExpress, which lists the marking (code) as well, I found the most likely candidate is the Torex XC62FP-series.

Turns out the marking scheme on the ICs seems to fit the specs in the datasheet perfectly:
The 3A0X marking confirms:
3: voltage of 3.something Volts
A: the "something" is .0, so "3A" = 3.0 V;
0: fixed, but probably unique for Torex;
X: changes with every lot, so doesn't mean anything to us.

Since the board has "3 V"  printed next to the pins of some headers, I was assuming from the start that U2 and U21 were most likely voltage regulators of  3 V. This together with the above data means I'm reasonably sure that U2 and U21 are Torex XC62FP3002PR, but I can't guarantee it. You may try these, but you do so at your own risk.

[ex830]

Hello
I have an Extech EX 830 AC/DC Clamp meter.
Please tell me wich is the procedure to calibrate the part of IR.
 
When I measure the hand temperature it shows me aprox. 60 Celsius degrees.
When I rotate VR11 and VR 13 to the left or to the right the temperature of my hand decreased to 46 Celsius degrees

[jitter]

Welcome to the forum.

Unfortunately, I don't have the calibration procedure. If it's worth the cost to you, you could have the meter calibrated (and if necessary, adjusted) by a company that provides calibration and repair services.
If it's only the IR range that's off, and the other ranges are working well, you might be better off buying a separate IR thermometer.

[ceut]

Hello,
I have calibration problem too on the IR Temp: it shows me -25°C in a room where I have +24°C since 1 week.
So I have opened it and I have found that 2 of the 4 sensor wires were about to pull out (bad factory wire quality and solder).
So I have cut all these wires and solder them again, and then put some glue (from a glue gun) on it.

Then I have moved the ROOM/T VR and the VR10 C/TEMP and it seems that all is OK now (I have just made this repair this afternoon so need to check if all is really OK).

I have found that VR2 is the Volt Calibration: I have changed it too.

And the last one: the VR DC/ZERO for the ADC, before I was having about 120A before zero-ing, and now I have about only 1A before doing zero.


Edit: I have received my UT-210E last week to have a more little clamp-meter, and after many EEPROM Mods, it's really a great cheap tool with high accuracy and faster than the EX830 ! 
I'm using now less my EX830, that's why I have started to try to fix it.