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Plasma cut 50

Thread starter #21
I use this video I don't have a powe supply to test but I use a phone charger that haves 9v output 350mA
In the pictures I'm showing the reading I get from the power adapter that is 13.50 and in the other picture is the reading touching the zener diode

To measure the zener diode and I'm getting a reading of 0.10 on the multimeter don't know if I'm doing it the right way please any help will be great, thanks !


Thread starter #23
I get abot 4 mm x 1.4 mm
Possibly this
MiniMelf (MMA), 0204 package
Metal Electrode, Leadless face
Who knows exactly how it's dimensioned

3.6 mm × 1.4 mm 0.25–0.4 W 200 V

Good catch on the band colors. Zener diodes will likely check regular diodes, but they are in-circuit.

Green - Schottky; Blue - Zener
i dint find it serch all ove the web but i found this part number or name dont know how to serch for this type of electronics,
(MiniMelf (MMA) Size 0204: length: 3.6 mm, diam.: :1.4 mm. Typical rating for resistors = 0.25 to 0.4 watt / 200 V)
this have similar characteristics , will this work to replace the one im looking for ??? thanks !


Thread starter #25
:banghead:I just notice something :banghead:when measuring:banghead: that is not the part I need This is the picture of the parts from the 2 ones that was not burn so sorry for not looking carfuly


Thread starter #26
Ok wait I'm stupid, I think I remove the black strip will trying to remove the glue, I just don't know what the hell im doing
Thread starter #27



Well-Known Member
Most Helpful Member
The circuit you have is very like;y to have similar bits nearby and for the Blank thing a resistor because of it's designation of R. A resistor marked 101 is 100 ohms. A "10" and 1 zero. so 221 is 220 ohms, 103 is 10K. Wattage you have to get by size,

When you measure "in-circuit", the parts around the part your measuring interact, so when using the diode test and you get 000 and 000 in both directions, you need to know if it's a surrounding part.

You may have to "reverse engineer". make a schematic from the PCB to enable better gueses.

Zener diodes, the ones with the (based in your pdf) colored band will likeley act like regular diodes unless they are something like 2.1V.

Your meter in the diode range may measure in mV rather than volts, so 686 is 0.686.

I have a $7.00 meter I got free that does this.

The value of a resistor that you can;t read, you may be able to make out parts of them and there may be a similar bit elesewhere on the board.

if you happen to find a bad zener diode that test bad in and out of circuit, your going to have to find a voltage source and a resistor to say limit the current to 1-10 mA and measure the voltage across it. For a 5.1 V zener diode, you;ll have ~0.6 one way and 5.1 the other.

A 9V battery and two 9V batteries in series would be a place to start.

Don;t forget to take photos before and after to check polarity.

For the dimensions, I have a dial caliper, so i blew up your jpg with the ruler. Measured the ruler for 1 cm for my screen in mm. Now i have a conversion to apply for other components measured on the screen.

So, if I wanted to measure the black resistor, I could measure the screen value of the diode and I know the real dimensions, so i can calibrate that way.
Thread starter #31
Ok before I star drawing the schematic I was looking to know the name of the particular part and I found a lot of similar ones in one of the pictures you can actually see the value of the parts Can I use one of this parts for replacement ? Mine is a plasma cut50 and not a welder, that I think this board at made for , again thanks for all the help!


Last edited:
Thread starter #35
I'm looking to see if I found a electric diagram schematic cause I know I cannot do the reverse engineering your mentioning I only know the basics of soldering and tutorial I found on YouTube but only basic stuff, here I found a interesting page http://www.emil.matei.ro/

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