Review of ELENCO Model M-2666K Digital Multimeter Kit

My wife got me the ELENCO Model M-2666K Multimeter Kit for Christmas as she knows how I love to toil in my basement workshop, restoring vintage electronic equipment and building new.

The Model M-2666K Multimeter Kit I am building is a full function Digital multimeter that includes such advanced functions as a diode/transistor checker and the ability to test capacitance up to 200uF! ELENCO is able to provide these advanced functions in this easy to build kit by embedding the processor to the main printed circuit board and assembling the function switch for you.

ELENCO offers both Digital and Analog Multimeter kits. In addition, they offer DC Power Supply kits, Radio kits, and Electronic Educational kits including their Snap-Circuit kits for young electronic enthusiasts.
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The multimeter kit also comes with a detailed assembly manual, shown below, which includes circuit theory, testing, and troubleshooting sections. The manual rivals what you would expect from a vintage "Heathkit" manual! ​​ I consider Heathkit manuals the "Gold Standard" of assembly instructions.

In addition, the manual comes with a section on how to properly solder components to a printed circuit board and identify electronic components, including determining the values of resistors and capacitors. 

The Model M-2666K Multimeter Kit manual can be used in a classroom environment, it includes a resistor reading quiz and identifies approval points so that the instructor can inspect work done before the student continues on the project. This is to insure that students adhere to the instructions so that there multimeter project is a success! 

Certain components, like the microprocessor, (round black circle to the left) and the selector switch come pre-assembled on the printed circuit board. ELENCO is able to provide advanced functions in this easy to build kit by embedding the processor to the main printed circuit board and assembling the function switch for you. Make no mistake, there is still plenty of soldering and assembly work to be done in this kit!

ELENCO separates parts into bags with section letters. The manual identifies which bag of parts is required for each section of the book. This allows the assembler to quickly get to the parts he/she needs and reduces the risk of losing other parts needed further in the assembly process.

Components, such as resistors and diodes, are attached to a cardboard identification strip. This ensures that the right component is picked and soldered to the printed circuit board.

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You assemble the multimeter kit in sections, at the end of each section you test a certain functionality of the meter. The first test is to see if you get the LCD display to work. When testing, you use the front sticker, with backing still attached, to identify the multimeter's settings.  

Soldering is fairly easy even for the novice, although, I wasn't too happy with the solder included with the kit and switched to a Kester Rosin Core 60/40 Solder after soldering the first couple components.  I didn't like how the solder included in the kit flowed. It could be that the solder included with the kit was lead free to meet some sort of mandated requirement.

Kester Solder on Amazon!

Most sections require a bit of testing and calibration at the end. You do need a solid electronics foundation to perform testing and calibration as the manual does not go deeply into these topics.

Calibration is typically achieved by comparing measurements with a "known" good reference. For DC Volts calibration, I am had both the ELENCO kit and my Radio Shack multimeter read the same 9 Volt battery. I adjust a potentiometer on the printed circuit board until the ELENCO multimeter reads the same as the reference Radio Shack multimeter.

Calibration of the low Amp (under 200ma) setting is achieved by connected the ELENCO multimeter in series with a "known" good multimeter, a battery, and a load which in this case a 47K 1/4 Watt resistor. The ELENCO multimeter should read the same as the reference multimeter when properly calibrated.

Calibration of the high Amp (20Amp) is a little more difficult and requires the adjustment of the distance of the shunt, circled in red, from the printer circuit board. It took me several try of desoldering/soldering the shunt to get the distance right and the Amp reading accurate.

I relied on my old Heathkit HP-23 Power Supply to provide a 6 Volts AC Reference Voltage, to be used for the AC Voltage and AC Current calibration steps.

This ELENCO multimeter employs a Piezoelectric speaker to indicate continuity. I used the alligator clip from a test lead to hold it in place while soldering it to the printed circuit board. In addition, you have to solder a lead from the center of the Piezoelectric speaker disk to the printed board. The connection on the speaker should be made as quickly as possible so as not to damage it. 

Calibration of the Capacitance meter built into the ELENCO multimeter is also done by adjusting the reading using a potentiometer to be the same as a reference meter. Make sure you use the SAME capacitor on both the ELENCO and reference multimeter during calibration.  The picture below shows two different capacitors used, which is a mistake.

The soldering process leaves a lot of brown flaky flux residue on the printed circuit board. While it probably will not affect the operation of the ELENCO multimeter, I think it looks unsightly. 

This is not a step in the assembly manual, I use a flux remover spray to eradicate all of the unsightly flux residue from the printed circuit board. I spray it on the board then work it into the areas where there is a lot of flux residue with a toothbrush then dry the printed circuit board with compressed air. Make sure you wear gloves and work in the well ventilated area as most flux remover can irritate skin and the fumes are noxious!

The ELENCO multimeter printer circuit board, devoid of flux residue!

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The ELENCO multimeter comes with an easy to assemble case. It is held in place with just two screws on the back of the case.

Here is the final product, the completed ELENCO Model M-2666K Digital Multimeter. It is a pretty impressive for being kit-built!

My ELENCO Model M-2666K Multimeter in Action!

This YouTube Video shows some basic DC Voltage, DC Current, Resistance, Continuity, Capacitance,  and Diode tests using my newly constructed ELENCO Model M-2666K Multimeter.

My Review

I sing the following praises of the ELENCO Model M-2666K Digital Multimeter kit:

• The M-2666K Digital Multimeter kit is a great value for the money. For roughly 35$, you get a high end multimeter you build yourself with advanced functions like Capacitance and a built-in Transistor checker. 
• Detailed "Heathkit" like assembly instructions.
• The kit also excels in parts identification and placement on the printed circuit board.
• Would make a great kit for an instructor led electronics class.
• Assembly time, about 10 hours in my case, was long enough to keep me engaged but not too long as to get bored with the project.

There are some negative, perhaps nit-picky, aspects of the M-2666K Digital Multimeter kit:

• I had issues getting the solder that came with the kit to flow correctly around the solder joints. This was remedied by using a Kester 60/40 Rosin Solder which provided shiny clean connections.
• It was tricky calibrating the high Amperage 20Amp setting, I spent about an hour desoldering/soldering the shunt components at different distances from the printed circuit board to get a correct reading.
• The Piezoelectric speaker used as the continuity buzzer is not very loud, probably because it cannot oscillate freely with the base being solder directly to the printed circuit board. I believe it would be louder if affixed to the printed circuit board using a foam "donut" mount. 
• The rubber protective holster feels "cheap" and does not grip the case of the multimeter tightly. 

Overall, the positive aspects of the ELENCO Model M-2666K Digital Multimeter kit far outweigh the negatives and the kit building process was a positive one.

This multimeter will grace my workbench for many years to come!