I was an idiot and may have destroyed my multimeter, any way I can test it?

[Cyber Akuma]

I am sure most of you probably can tell from the title can already tell what happened but let me get into it. I have a Klein MM400.
 
My father asked me to look into a charger for his wireless drill, he had already opened up the AC adapter for some unsafe reason and told me he thought the transformer itself was damaged. It has been a while since I last used a multimeter and had forgotten hot to properly use it, and stupidly plugged the lead into the 10A port. I tried checking if any DC voltage was coming out of the transformer but of course the display said nothing, so then I wanted to make sure AC voltage was even coming into the transformer.
 
Yes, I am fine, the pop was thankfully at a distance from me on the transformer itself.
 
The multimeter still turns on, I plugged the red lead properly into the other port and it still seemed to measure AC voltage ok. But since this multimeter was the most advanced electronics testing equipment I had in the house, and it's now possibly damaged, I don't know any other way I can test it's other functions to see if it's even still working properly. I don't even have any other cheaper multimeter to check it's fuses to see if they blew. I will need to replace the leads as the incident seems to have taken a small chunk out of the tip of the red one, but I have no idea if this is still working, if it's fuses blew but it's otherwise fine, or if it's permanently damaged now. Yes it's no $100-300+ Fluke, but it's no $15 Radioshack special either and I would like to try to see if it's still working properly before replacing it.
 
Here's pictures of the inside:
 

 
 

 
 
(Damn was it annoying to screw the PCB back into it after the photos, mainly the part where the selector dial is held in place by two tiny spring-loaded ball bearings that were very very easy to lose or mis-align, still not 100% sure I put that part back together right as the selector switch feels a bit stiffer than before)

[WimWalther]

If the 10A circuit is fused, you very likely took out the fuse. If no fuse, then it's extremely likely that SOMETHING blew out, either in the meter or the device under test.

Is that xfmr still outputting voltage?

Anyway, that piece of heavy, bare copper wire that looks like a W is probably the 10A current shunt. If it's not all blowed up & crap then the meter is probably just fine. But like I said, something very likely blew.. somewhere. So find & fix it.

ETA: Only hi-end meters tend to have fuses for the high current range. Inexpensive units run bare and unprotected. A slip like you made typically blows traces associated with the high-current shunt off of the board, leaving ugly black burn marks.

[Kleinstein]

If the mishap happend at a relatively low voltage ( like < 200 V), chances are high that only the 10 A fuse is blown. The diode test of the meter should likely still work and could be used to check the fuse (out of the holder).

A proper fuse may be expensive and one may use a lower rated fuse for a few initial tests - not to oder a $10 fuse for a broken meter. 

[wasedadoc]

Most likely the 10A fuse blew.  The resistance ranges do not use that fuse.  See if the resistance ranges are alive by switching to them and shorting the probe tips together. Should read zero or close to it.  If so, remove the 10A fuse and put it between the probe tips.

[WimWalther]

Oh look, there's a big ol 10A fuse in there. Dang thing was covered by some notify on my screen.. =/

It's likely shot.

[Cyber Akuma]

If the 10A circuit is fused, you very likely took out the fuse. If no fuse, then it's extremely likely that SOMETHING blew out, either in the meter or the device under test.

Thre are two fuses in it (the white ones in the photo) one is listed as 600V 500mA and the other as 600V 10A, so it looks like it does have a fuse over the 10A. No visible signs of it having blown though, but it's not transparent.

Is that xfmr still outputting voltage?

Didn't check, not sure if it would be a good idea to plug that thing back in after this. The reason it blew was because I was using the 10A port right? I can't imagine why it would not be causing a short or anything while it was plugged in but caused a bang like that as soon as I put the test leds on the AC side of the input wires. They were directly coming in from the AC jack itself so there shouldn't have been anything that got crossed.

Anyway, that piece of heavy bare copper wire is probably the 10A current shunt. If it's not all blowed up & crap then the meter is probably just fine. But like I said, something very likely blew.. somewhere. So find & fix it.

The M-shaped one labelled R34 you mean? I notice there is a glass component connected to it, I think it might be a diode?

If the mishap happend at a relatively low voltage ( like < 200 V), chances are high that only the 10 A fuse is blown. The diode test of the meter should likely still work and could be used to check the fuse (out of the holder).

It was US AC current, so yeah, 120V.

So that diode is for the continuity test function?

A proper fuse may be expensive and one may use a lower rated fuse for a few initial tests - not to oder a $10 fuse for a broken meter.

Well, is there a way I can test if it's working before ordering a replacement fuse without needing another multimeter?

Most likely the 10A fuse blew.  The resistance ranges do not use that fuse.  See if the resistance ranges are alive by switching to them and shorting the probe tips together. Should read zero or close to it.  If so, remove the 10A fuse and put it between the probe tips.

So basically use the resistance measurement as a continuity test to check the fuse? How can I be certain that function is still working though?

[bdunham7]

The Klein MM400 is a perfectly OK meter and has reasonable 600V ceramic fuses. I'm 99% sure you just blew the 10A fuse, no need to disassemble it so far.  Even the tip of the test lead can be touched up with a file, sandpaper or bench grinder.

https://www.kleintools.com/catalog/test-measurement-accessories/fuse-6x32-10a-600v-mm300400

[wasedadoc]

So basically use the resistance measurement as a continuity test to check the fuse? How can I be certain that function is still working though?

If the restance ranges show zero or near zero when the probe tips are shorted and OL or dashes or something similar when the tips are not shorted, they are working well enough to test the 10A fuse.  If the fuse is OK it will give the same reading as when the probe tips are shorted together.  (One probe in the Common jack and the other in the Volts/Resistance/Continuity/Diode jack.)

[Gyro]

...
Thre are two fuses in it (the white ones in the photo) one is listed as 600V 500mA and the other as 600V 10A, so it looks like it does have a fuse over the 10A. No visible signs of it having blown though, but it's not transparent.
...

Visible signs of a 10A 600V fuse having blown would be a bad thing!

[TimFox]

You should sit down before looking up the price of a proper 10 A replacement fuse, rated for DMM service.

[Ian.M]

Do *NOT* attempt to test the 10A fuse in circuit - it must be removed from its meter, if you are using the same meter to test it.

They are ****ing expensive because they are specially made to high quality standards with a reinforced tube and arc suppressing filler to break a high energy circuit without exploding (up to the meter's CAT rating), or at least to contain the explosion enough that it doesn't breach the housing and try to turn you into a crispy critter.  Then of course there's the usual retail ripoff markup for anything sold in small unit quantities with safety certification!

[WimWalther]

You should sit down before looking up the price of a proper 10 A replacement fuse, rated for DMM service.

The large HV fuses which protect meters like the Fluke 8050A are maybe even more expensive.. like $24 a pop, last I looked.

Fortunately, the 8050A high current range is covered by a standard AGC 2A, common & cheap.

[Zero999]

Remove the fuse and check it with the multimeter's continuity setting, which will work without the fuse in it.

It's easily done. It's why I use a meter with an idiot alarm, which beeps if the lead is inserted into the current socket and the meter is set for voltage.

[Cyber Akuma]

The Klein MM400 is a perfectly OK meter and has reasonable 600V ceramic fuses. I'm 99% sure you just blew the 10A fuse, no need to disassemble it so far.  Even the tip of the test lead can be touched up with a file, sandpaper or bench grinder.

https://www.kleintools.com/catalog/test-measurement-accessories/fuse-6x32-10a-600v-mm300400

Good to hear it would be just the fuse that blew. Not sure how well the tip can be touched up though since it kind of took a small chunk out of it. But a new set of leads cost about half what the multimeter itself cost, so I can hopefully go that route instead of buying a new set.

If the restance ranges show zero or near zero when the probe tips are shorted and OL or dashes or something similar when the tips are not shorted, they are working well enough to test the 10A fuse.  If the fuse is OK it will give the same reading as when the probe tips are shorted together.  (One probe in the Common jack and the other in the Volts/Resistance/Continuity/Diode jack.)

Yeah, the fuse is definitely dead. Resistance shows no difference as if I was not connecting the leds to anything, and the continuity test shows no continuity.

You should sit down before looking up the price of a proper 10 A replacement fuse, rated for DMM service.

Do *NOT* attempt to test the 10A fuse in circuit - it must be removed from its meter, if you are using the same meter to test it.

They are ****ing expensive because they are specially made to high quality standards with a reinforced tube and arc suppressing filler to break a high energy circuit without exploding (up to the meter's CAT rating), or at least to contain the explosion enough that it doesn't breach the housing and try to turn you into a crispy critter.  Then of course there's the usual retail ripoff markup for anything sold in small unit quantities with safety certification!

I checked, they're $10-13, ouch.

And yes, I tested it outside the multimeter.

Remove the fuse and check it with the multimeter's continuity setting, which will work without the fuse in it.

It's easily done. It's why I use a meter with an idiot alarm, which beeps if the lead is inserted into the current socket and the meter is set for voltage.

Would have been a useful feature in this case. I checked and there is apparently a MM420 model that is basically the MM400 but with a warning if the leads are in the wrong sockets. Wonder why I didn't just get that since the price difference is small, either it didn't exist when I bought this or I might have read of some issues with the 420.

So the 10A is just to measure current over 500mA and nothing else? I used the 10A because I was worried that the adapter was definitely going to be outputting more than 500mA. Does the current only matter when you are measuring current and not something else like voltage even if the current would be above 500mA?

[Zero999]

So the 10A is just to measure current over 500mA and nothing else? I used the 10A because I was worried that the adapter was definitely going to be outputting more than 500mA. Does the current only matter when you are measuring current and not something else like voltage even if the current would be above 500mA?

The actual current flowing depends on Ohm's law:

I = V/R

The meter will have a high input resistance, typically around 10M Ohms, so the current will be tiny. If the voltage source is 100V and can supply 10A, only 10µA will flow because of the high resistance.

The current setting should never be connected to a voltage source. It will have a very low resistance, which is why it drew a huge current, causing a loud bang and the fuse to blow.

[BeBuLamar]

Or you can simply use the meter without the fuse. Don't measure current with it and it would be just fine.

[TimFox]

You can measure low values of current through the 10 A switch setting and 10 A fuse, but with lower resolution.
However, as stated above, never use the 10 A connection to measure any voltage:  the two panel connectors go directly to a very low resistance "shunt" to obtain probably 100 mV into the voltmeter circuit at 10 A (0.010\$\Omega\$), which is why there is a 10 A fuse there.
On a typical DMM, the input resistance in voltage mode (using COM and VIN terminals) is 10 M\$\Omega\$, although some cheap ones are maybe 1 M\$\Omega\$ and expensive meters often have very high input resistance on the low-voltage ranges.

[TimFox]

Or you can simply use the meter without the fuse. Don't measure current with it and it would be just fine.

This is why one often sees such meters at one's employer that don't work on the 10 A range (where a technician forgot to inform his supervisor what he did), along with ones sold through eBay at low prices.

[bdunham7]

Do *NOT* attempt to test the 10A fuse in circuit - it must be removed from its meter, if you are using the same meter to test it.

I'll agree that you should never test the innards of a meter with itself if any covers are off, but in the case of this and most meters with current fuses, simply running a single lead from the normal V+ input to the current input and then selecting continuity is a safe and reliable way of checking the fuse. 

[BeBuLamar]

Or you can simply use the meter without the fuse. Don't measure current with it and it would be just fine.

This is why one often sees such meters at one's employer that don't work on the 10 A range (where a technician forgot to inform his supervisor what he did), along with ones sold through eBay at low prices.

Actually I blew the fuse in my work Fluke 87V often and I always replaced the fuse because I don't have to pay for it.

[Veteran68]

So the 10A is just to measure current over 500mA and nothing else? I used the 10A because I was worried that the adapter was definitely going to be outputting more than 500mA. Does the current only matter when you are measuring current and not something else like voltage even if the current would be above 500mA?

Since I don't think I saw this question addressed directly: the "A" settings on your meter are there to measure current (i.e. Amps), never voltage. Current measurements require your meter probes to be IN SERIES with the circuit under test, meaning you break the circuit and place the meter probes in line to complete the circuit through the meter. The big 10A fuse is on the 10A probe jack; since you have a 500mA fuse you should have another port labeled for mA or mA/uA which protects that jack when measuring small currents. Voltage measurements do not use the fuses.

Placing probes from live to neutral when measuring current, as you would if measuring voltage, is directly shorting them together with only the very low impedance current shunt as a load. Pretty much the same as if you stuck a fork in an electrical outlet! Fortunately Klein are not bottom barrel meters so its damage is likely limited to the blown 10A fuse. Cheaper meters could potentially break down even more catastrophically (though unlikely at only 120V mains, as the energy isn't all that high compared to 230V or 480V or higher systems). If it weren't fused at all, the meter would be damaged probably beyond (practical) repair.

No offense intended, but I strongly suggest you look up how a multimeter works, because this is basic DMM operational knowledge and without it, you might not only destroy equipment, but (at least with an unsafe meter) potentially hurt yourself, burn down your house, etc.

[ledtester]

Recently I've seem some meters from aliexpress being shipped with a warning sticker over the current inputs. And after my dad blew out a cheap meter by making the same mistake I put a piece a tape over the 10A jack - at the very least it will serve as a reminder that extra care needs to be taken when using that input.

[alligatorblues]

A cheap and dirty continuity tester is a flashlight with the battery cover unscrewed and the circuit bridged by the questionable fuse.

[JustMeHere]

Pull out the 10A fuse that you probably blew.  And since that thing doesn't seem to have a port for mA, also pull out that fuse.  Wait awhile, possibly overnight.   Give the thing the smell test.  The chances you blew one or both fuses is a certainty.  The chances you broke anything else is slim.  There is  no visible damage on the switch.  The other functions are isolated from the amp measurement side.

[Stray Electron]

A cheap and dirty continuity tester is a flashlight with the battery cover unscrewed and the circuit bridged by the questionable fuse.

  I was going to suggest that to the OP.  When I was young and started tinkering with electronics I made simple continuity testers by taking a bare piece of solid conductor copper wire (from a piece of Romex) and wrapped it around a D sized flashlight battery and bent a loop in  one end to hold a flashlight bulb pressed against one of the battery terminals and then the other end of the battery and the 2nd end of the copper wire as my test points.  It's crude but something like that would work fine for testing fuses and other low resistance items.  Don't use something like this for testing anything with power applied to it!  Other than perhaps a small dry cell battery.

   Not to be dick about it, but buying a few of those stupidly expensive fuses will teach you to double check your meter settings before taking any reading with it. Just be glad your meter had a fuse or you would be buying a new meter!

  I'll also suggest that you go down to Harbor Freight and buy one of their cheap $5 meters and use it for things that don't require precision or that involve safety related items.  I got several of them when they used to give them away and they're surprisingly good meters. Mine has lasted me for over ten years so far.  I keep one in my tool box and use it more than all of my GOOD meters combined.