Like most people these days, I strive hard to live by the three "R"s. Reduce, Reuse, and Recycle. Under the "Reuse" category, I decided to give this old Micronta Model 22-027, 8 Range VOM (Volt-Ohm-Meter) a new lease on life.
Appearance wise, my Micronta 8 Range VOM was in pretty good shape.
Uh-oh, someone (me) left an Alkaline battery in the Micronta VOM and it corroded the negative contact. I am not sure why Micronta choose to use a red wire to connect to the negative contact.
I decided that a chrome plated brass hasp from a wooden craft box would make a good replacement for the negative battery contact.
I cut the metal hasp, using wire cutters, to just a hair bigger than the channel cut into the Micronta VOMs plastic battery tray so as to make sure it was a firm fit. I then used the blade of a screwdriver to press fit it into the channel in the battery tray. I then soldered the red (negative) wire to the new battery contact.
The meter needle did not point to 0 on the DC Volts scale when no voltage was applied, so I "zeroed" the meter with the adjustment screw on the center of the Micronta VOM.
I also was unable to properly Zero the Ohmmeter function of the Micronta VOM using the Zero Ohms Adjustment thumbwheel on the front of the meter. Adjusting the trimmer potentiometer inside the meter allowed me to adjust the Zero Ohms Adjustment range so as to allow proper Ohmmeter calibration.
My repurposed Micronta VOM was going to me used exclusively to monitor Voltages and to troubleshoot issues with my home brew vacuum tube regenerative radios. As such, I swapped out the test probes with small alligator clips from old alligator leads so that the Micronta VOM leads could be securely connected to component leads and Fahnestock clips in my home brew radios.
Here are the finished Micronta VOM test leads with repurposed alligator clips.
The repurposed alligator clips on my Micronta test leads where sticking in the open position as the spring could not overcome the corrosion at the joints. A drop of Labelle 107 Model Train oil at at the alligator clip joints allowed then to open and close smoothly.
My repurposed Micronta VOM put into action troubleshooting a newly built Regenerative Radio I just built!
2 Comments
Daniel D Buchalter
8/23/2019 05:04:40 pm
I just picked up one of these and cleaned off that negative contact plate (it was still salvageable) and I think the meter works (a weak battery at least moved the meter needle) on the 1.5 VDC setting). The mystery I am trying to solve is what if anything can one do to prevent battery drain as there is no on-off switch. Is the circuitry, which looks pretty simple to my not very sophisticated eye, somehow set up so that there is no drain except when a measurement is being taken? I've looked at the contacts on the inside, at the plug in points for the removable probes, and they don't seem to have a 'current interrupter' function, comparable to the traditional headphone jack setup that at least in portable radios disconnects the built in speaker when an earphone or headphone is plugged into its jack. So, if it really doesn't consume power except when taking measurements, Is this an advantage of an analog meter? I think even a digital meter doesn't suffer from power drain unless it's left 'on', and unless there's an auto power off feature at least, the digital display if left 'on' would always consume some power.
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Jim Dodson
9/17/2019 06:32:25 am
I bought a Micronta 22-221 at a sale for $2. I need test leads. Do you know where I can fins these? Thanks
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Who Writes This Blog?John is an IT professional from Cleveland, OH who enjoys amateur radio, ham radio, metal detecting, Archives
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