How I fixed my $1.48 Thrift Store Analog Multimeter.

[@Ranger42]

Great instructional video! You just saved me having to go out and buying a new Multimeter. Had an old Analog Etek 10729 I bought at Walmart years ago and hadn't used it since. Thought it was the battery but that didn't work and could not see a fuse. After watching your video, I removed the entire backing and found the blown fuse, which I change and works great. Thanks!

[@tomallen100]

Good idea to leave the battery out until you need to use the resistance portion especially if you only use it every couple of years. You can still read voltages and current without the battery installed.

[@rhshel]

Amen. That goes for anything taking dry cells left for long periods! They leak and can destroy contacts and equipment.

[@rwbishop]

As others here have noted, if you leave the battery out till needed, you'll never have corrosion issues. Also, when I install batteries (in anything), I like to date them. If the date can be so positioned to be visible without removing backs/covers, so much the better. I also have a little 'beater' meter... 99.997% of the time it's used for checking continuity, and/or looking for the presents or lack of power when a test light isn't handy. If lost, damaged or swiped, who cares! I have better meters for more involved uses...

[@lyttgardner6456]

There is another problem this video did not cover. When these little analog multimeters have not been used for years (like my Craftsman 82401) then large rotary switch develops corrosion on the contactor. Have to pop the circuitboard up and rub the 3-prong metal contactor (business end of the rotary switch) with fine grit sandpaper. I used 400 grit paper and that solved the problem. I was seconds away from throwing this in the trash when I realized--the batteries corroded in a closed environment, this may have added (airborne) corrosive battery residue to any moving metal part. So the lesson is: its not just the battery and the fuse that can cause a dead analog multimeter. X2 on Mr. Allen who said to leave the battery out.

[@CheapGeek]

Checking a battery is easy. 1. All you need to do is set the multimeter to VDC or DC, set the voltage range one level higher than the battery voltage. For example if you have a 6 volt battery set the voltage range on the meter to 10 VDC or 12 VDC. 2. Connect the red lead to the plus ( + ) the black lead to negative (-) on the battery. 3. Read the meter. 4. :)

[@CheapGeek]

If you've checked the fuse and the battery and it still doesn't work, check the test leads. If the leads are good. I'd say the multimeter has problems.

[@micron2z]

Thanks for the video! I bought one of these last year, but had not way to make sure it was still functional (I'm an electronic novice). The one I got only has the ground lead. I'm going to see if I can make a positive lead. Have a great day!!

[@CheapGeek]

Sweet Good Luck! I made a lead from an alligator clip and a piece of speaker wire. Worked pretty good.

[@Rabbit.760]

Yours is way more smoother on the response than mine... measuring ohms is all wack

[@CheapGeek]

Ha! It would be a good ghost hunting EMF detector.. with some slight modifications..

[@theLuigiFan0007Productions]

CheapGeek Where could I get new protection diodes and shunt resistors? How would I determine which diodes to use? I.... kindof made the mistake of.... forgetting to set it to volts when measuring 120VAC... it was on the 250mA range. Yeah, that's a really, REALLY bad mistake to make. I heard a small click (like an arc) and it buzzed loudly. I'm quite experienced with designing digital circuitry and small analog stuff, but I have no idea how to check what got cooked besides the usual unsolder one lead and measure technique. It's the GMT-12P (which looks identical to your 12A) and is likely a newer model of the same thing (but still quite old) and lacking a fuse holder. I'v personally used it before I got my first DMM to regularity measure big DC supplies, line voltages and the like.The movement is unharmed (thanks to the now cooked diodes) and still measures AC voltages correctly. On the DC scale, it measures infinite voltage on the 10V setting (needle pegs to the right) with a single AA battery, reads less then 0 on the ohms (pegs again). The contacts on the PCB are in great condition, nothing is visually scorched, not even the shorted protection diodes. How would I determine which kind of diode to use and and what tolerance of resistor is acceptable?

[@Sparks68]

Mouser Electronics is the first place I'd try. Google for the parts you need. There are others like DigiKey Electronics. Amazon has some stuff but they're typically more expensive. If you have the schematic, component list by schem. ref. des. and a diagram showing parts locations on the PCBs, also by ref. des., it should be easy to figure out what you need. If you cannot find the exact value you need for a resistor, consider putting two or more in parallel.

[@theLuigiFan0007Productions]

jlind52 Thanks for the info, but I do know where to buy components. Lately I buy from AliExpress in packs of hundreds. What type of diode is generally used for a protection diode? The resistors are 1.5% tolerance I think. I still haven't found any good info of how exactly analog meter circuits work. Would you have any links for that? Or I guess I could just replace all the components around the movement. I'm not very good at reverse engineering analog circuits, especially if I have no schematic. I can make a schematic if I need to, but that will definitely take a while. It's likely a single sided PCB.

[@Sparks68]

My Heathkit IM-105 VOM (aka Weston 660) has 1N4149 protection diodes. I've also seen remarks about 1N4007 being used on a very old VOMs (model unknown). The specific diodes used will be somewhat circuit design and specific meter movement dependent, combined with what the VOM design EE wanted the meter movement to survive. They're generally fast silicon diodes, and they're selected for a specific forward voltage required before current will flow, typically in the range of 750mV - 1V, plus the forward current it can withstand. The forward voltage needs to be high enough to allow the meter to function, but low enough to protect it from an over- voltage that would burn the coil out. This is what the bare meter is rated for, NOT the VOM! If a diode burns out (goes open) from overload the meter *will* be destroyed. Also have an *old* type 3 Triplett 310-C, and it uses a diode assembly with both diodes in the same package. Schematics only give a Triplett part number. I would suggest getting a schematic for the VOM. A VOM works by using voltage drops across precision resistors. It's not that complex, although it might seem so because of all the ranges involved with the rotary switch, and selection of resistance, voltage or current. The only thing a VOM uses the internal battery for is measuring resistance. It's not used at all for measuring voltage or current. See this article in Wikipedia: en.wikipedia.org/wiki/Multimeter If you can, get the manual for the Heathkit IM-105 VOM which has its operation explained in detail near the end. All VOMs work in the same manner although the specific resistances used will differ. You mqy also be able to find the schematic for an old Triplett 310 Type 3, 4 or 5, which has a very straightforward schematic in it. You can see from it how the VOM uses precision resistors for resistance, voltage and current measurement. All VOMs are about the same in this regard. It's specific resistor values and which diodes are used that are different.

[@theLuigiFan0007Productions]

jlind52 That's the kind of useful information that I wanted, thanks a lot! :D

[@Sparks68]

Are you sure the meter protection diodes are blown? Would just about guarantee the meter coil would be roasted to well done. The diodes are mounted in parallel, with one in one direction and the other in the opposite (i.e. anode to cathode and cathode to anode) across the meter terminals or on very wide board traces going directly to them a very short distance, to prevent a board trace from acting like a fuse. Since they're across the meter coil like that, it's not possible to determine if either one is open or shorted unless you remove them. And you shouldn't be checking their forward/reverse continuity across a bare meter anyway. It bangs the meter needle on the pegs which isn't good for the meter needle or its pivots. The usual problem when connecting a VOM to a live circuit is blowing one of the precision resistors that was switched into path for the range it was in. I have an old HeathKit IM-105 that I built over nearly 40 years ago. Loaned it to a guy (last time I loan a VOM out) and he did what you mentioned: connected it to a live circuit in resistance measuring mode. Popped a 19.5 Ohm 1% resistor that was switched in for the resistance range he used. Nice little burn mark on the board under it. Not hard to spot. Finally replacing it as it's sat on a shelf for 25 years. Can't get a 19.5 (at any tolerance) at a reasonable price as it's not a common value, which is why I set it aside. Got a pair of 39 Ohm 1% which will give the required value with the two of them wired parallel to replace it. Haven't been able to use any of the resistance ranges for other than continuity checks since then. Look for burned out resistors and watch the wattage for any you replace as you want to meet or exceed that. Don't use wire wound unless you're replacing a high power rating wire wound typically found right at the special high voltage inputs (if your meter has them), as they introduce inductance which then creates a combined impedance greater than their pure resistance to AC signals. Good luck working on it.

[@rhshel]

for a buck and a half you found a real bargain good for you!

[@ZambalesBenny]

Thanks. How do I check batteries. I got a drawerful:)

[@maffytaffy1914]

my needle is not working well since the fuse got busted. i have an analog multimeter when i set it to the lowest reading the needle wont zap to right like it used to it just went to the middle. please help. im just new on this thing.

[@JPahang27000]

+mastur bee hi~i also have this problem the fuse got busted and then other thing wont funtion anyone except the beep beep sound.

[@JPahang27000]

+mastur bee wont funtion anymore

[@Sparks68]

Simple: quit measuring amps with it the way you have been. It's intended to measure current going through an electrical appliance or device that runs on electricity, not the current capacity of a battery, the wall outlet or another power source by itself.

[@froilan2280]

what if i already check the fuse and the battery and still its not working pls help thanks

[@TooLateNoobs]

yea, but how? i am a noob so dont yell at me.

[@SMFARHADUZZAMAN]

What is the value of the diode used in sanwa analog multimeter.plz someone help me.my meter is dead.i think that diode is dead but i cant see the value bcoz its burn out

[@nerfnerfification]

if no luck finding circuit for your meter, try a 1N4007 - they are pretty common and were often used in the older meter circuits.

[@ryansmith-kc7jw]

do u use it for ghost hunting ?lol

[@CheapGeek]

I wouldn't measure anything over 120 volts with this. DC up to 36 volts ia bout all I've measured with it. :)

[@Rabbit.760]

Fuse protected

[@Quimerateck]

got the same but i cannot zero it :S

[@felixcat4346]

How insipid is this?