Zero analog multimeter?

[Capt. 2110]

I recently got a free ArcherKit 28-4013 analog multimeter, and I'm trying to restore it. When I opened it, the battery was leaking on everything, and it ate at the chrome on one of the battery terminals. I've been messing around with it after cleaning it up and replacing the battery, and I've found you can't zero the meter when it's set to measure ohms. Does anybody know what's wrong with it? I'm thinking it was dropped once(or a couple hundred times), since the lens is cracked badly on one side, and the thick plastic case is pretty beat, and has a small crack too.

 

[Chuck(G)]

The battery is used only for resistance measurement, correct? After you've ensured that there are no high-resistance circuit paths left in the meter works, you should find a trimmer pot that allows you to zero when the test probes are shorted together. On, say, a Simpson 260, there's a knob to the right of the selector switch that says "zero ohms". On your Archer cheapie, it's that little red thumbwheel above the input jacks. It could well be corroded or dirty. The same effect can be seen if the range selector switch is dirty or corroded.

 

[Capt. 2110]

Well, I've cleaned the contacts on the power/mode dial, and it didn't help much. I've been fiddling with the thumbwheel, and it doesn't move the needle much. The most I can get it past is about 3.5. And The negative wire is shot, so I'm just jumping the ports to get it to work. I posted some pictures to show a rough idea of its condition. I noticed a lever after taking the lens off, and I found moving it moved the needle(to an extent). I tried moving it, then turned the meter back on, and it stuck at 4 again. It's almost like the needle is catching on something, but I can't find what...

 

[Chuck(G)]

Are you saying that the meter movement is shot? That can happen, as they needle moves on jeweled bearings and uses a very fine spring to return it to its rest position.

So, with the power off, does the meter zero on all scales (volts, amps, ohms)? If not, you've got a problem with movement that's not easy to fix.

 

[Capt. 2110]

Then it's the movement. How do I replace the assembly for the meter?

 

[Dwight Elvey]

It is possible that the meter is still OK.
It is common for the meters to get small pieces
of iron or magnetite caught in the magnetic field.
When this happens, the coil will run into the
piece and stop, like you are seeing.
You need to use light and a magnifier to see it.
If you find it, it can be dragged out with the point
of an iron sewing needle. It can then be removed with
tweezers.
The movement is not likely replacable as these are
not manufactured any more.
Besides the physical size, you need to also match
the full scale current and movement resistance.
If you can find one to fit, its resistance is less
and the same or lower full scale current, you can
get it to work.
Most meters are 20K ohms per volt. The movement would
be 50 ua but You'd need to check the series resistance
on the lowest DC scale to determine the meter resistance.
It is not a good idea to use an ohm meter to measure
a meter movement directly, as it can damage the
movement.
Dwight

 

[KC9UDX]

Then it's the movement. How do I replace the assembly for the meter?

So you can't get it to zero to the left side in any mode other than resistance, with the mechanical adjustment on the meter mouvement?

If so, is it too far left of zero? If so, the needle may be bent. If not, it's likely what Dwight says.

 

[Dwight Elvey]

He has been talking about zeroing ohms. On a vom, that would be
not enough amplitude or something is blocking it.
Since there was rust, there could be a lot of particles that
would stick to a magnet.
Dwight

 

[HattyDamp]

Hi...i am a new user here. My simpson meter,its a 260 (yellow case) analog meter doesn't zero up on ohms function ,,the needle reading stays towards the center of the scale and cant be zeroed up on the ohms function..batteries, fuses have been replaced. The needle goes to zero on voltage scales.Could be a resistor? but i have no idea which one to replace to correct this
Meters are used to teach children and i have several with this problem so help would be greatly appreciated