Multimeter repair

[Raqumup]

Anyone know any electronic gurus that can fix multimeters? I have an old craftsman meter that a new guy at work put the amp meter across a car battery and damaged something on the inside. I already replaced the fuse and did some basic checks on it and something on the board inside is damaged. Thanks in advance.

 

[Sevenhills1952]

To start you need a schematic diagram of it. Check online and print it. Without that you're lost.
If you know what setting he had it on, look at the switch contacts which may be burned. Worst case is the meter itself got fried (open). You can check that with another meter on ohms. It will have two connections and the wire wound movement should measure (I'm guessing) about 10-100 ohms.

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[brownbagg]

cheaper just buy need one, the old craftman multimetere was cheap anyway, it properly blew the shund in it, which is common, some are replaceable like a fuse

 

[Stuart in MN]

cheaper just buy need one, the old craftman multimetere was cheap anyway, it properly blew the shund in it, which is common, some are replaceable like a fuse

I think that should have been "Probably blew the shunt."

Unless you're handy with electronics and want the challenge of making repairs, it may well be time to just buy a new one.

 

[Sevenhills1952]

The priority is meter movement itself. If it works on other ranges there's hope. If the meter itself, which is easy to check with an ohmmeter, is ok you might attempt repair. If it's open, I'd forget it.

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[Joe From NY]

I think that should have been "Probably blew the shunt."

.

Or “properly blew the shunt”


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[Raqumup]

ok cool, thanks guys. i did figure out that this meter is a re badged extech EX470. ill look for the schematics online, anyone know a place i might find them? i did go ahead and buy another meter. i got the extech EX570. basically the same meter but this has a few more things like min. max. i still want to try and fix the old one. i will probably just try and fix it myself now that i bought another one.

 

[dogdog]

ok cool, thanks guys. i did figure out that this meter is a re badged extech EX470. ill look for the schematics online, anyone know a place i might find them? i did go ahead and buy another meter. i got the extech EX570. basically the same meter but this has a few more things like min. max. i still want to try and fix the old one. i will probably just try and fix it myself now that i bought another one.

I have the ex470... you did open it up and change those two fuses inside ?

one is a 20A and the other is a 5 or something in the daughter board setup.

 

[Sevenhills1952]

Does meter move on other ranges?

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[Raqumup]

Yes. The fuses are good. The other functions are working just fine. I can’t seem to find any schematics for this meter. Anyone have any links for where I might find it?

 

[SGKent]

I have an old craftsman meter

The EX-470 is only 3 to 6 years old. To me old is 20 to 60 years old. Here is the manual showing the fuses etc. https://www.google.com/url?sa=t&rct...EX470_UM.pdf&usg=AOvVaw0g3higfDPh5tFZKka2V56G

You can post the Craftsman model number if you know it.

start by pulling a fuse, one at a time and checking it with the new meter. If it blew something you will see a burn in one of the traces. You can use the other meter on ohms or continuity to check the traces and follow them. Put the meter in amp scale, then put one probe from your new meter on the old probe tip and the other on the fuses. It will show continuity between the old probe tip and the fuse, follow to the other side of the fuse, then the trace to the next point. You don't need to check the common side because you know the other functions work. My guess, and it is only a guess is that the fuse is blown but it looks good visually. I've done this a couple times in my life and it is always the fuse. Make sure you get the right size fuse. Sometime there are spares inside the back. If they are gone then someone has done it before and may have put the wrong fuse back in. Usually the inside of the case specifies what the fuse sizes are.

 

[Bigbandguy]

ok cool, thanks guys. i did figure out that this meter is a re badged extech EX470. ill look for the schematics online, anyone know a place i might find them? i did go ahead and buy another meter. i got the extech EX570. basically the same meter but this has a few more things like min. max. i still want to try and fix the old one. i will probably just try and fix it myself now that i bought another one.

Craftsman had the bad habit of changing specs on their re-badged stuff. They would do things like change color coding of wires and other creative chickens*** to make servicing their stuff have to go in house to them. I am convinced that this sort of **** contributed to the demise of Sears. I got bit real bad by an AC exhaust fan motor at a time when I had to save up money to buy it. The resulting fire burned up any idea of future purchases from Sears EVER. Moral of the story is that the circuits on the rebadged unit may have some unique properties.

 

[Sevenhills1952]

Yes when you said old I was thinking analog, not digital. About all you can do is check the two fuses. If everything else works you could use another meter to check current.
Putting it across a battery on amps would have been a lot of current for a few milliseconds! I would have to see an actual schematic diagram to help, but taking it apart, put on that range he had it on, as others said probably an open shunt resistor if it was on a high current scale. That shunt most likely burned quickly so you can't read value. Depending on range (was it 20 amp range?) it could be really low like 0.01 ohms.

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[Raqumup]

i guess you guys are right about the age. i really thought i bought this meter back in the early 2000s but i guess not. i cant find any documentation about the copyright for the craftsman pro model 81079. it is basically the same as the EX470A, it even has EX470A printed on the board inside. and the EX470A manual you can download has a copyright of 2013-2016. i have bought a new meter, not here yet, should get it from amazon on 7/9/19. i got the EX570. same meter basically but this one has min/max capabilities, and some other stuff too. still want to try and fix the old one, if nothing else, maybe i can learn something. still have had no luck finding schematics for this meter. anyone have any good places to look for them???

 

[Raqumup]

so after being able to sit down and look at the meter closer, i noticed the 20A fuse was moving around. the spring clips that hold it in were a bit bent and not holding the fuse tight. once tightened, i tested it, and it works just fine. thanks for your help and ideas. just goes to show that most of the time, it always comes back to the basics.

 

[SGKent]

you can never have too many multi-meters.