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Hi all I'm looking to fix my machine I'm in this forum because here are all the experts in this field, I don't know much I have fix other electronics but this is my first machine whit hi voltage parts and I will like to be safe first before star the fix
The "commons" of the primary cause some very difficult issues with trouble shooting. Don;t probe the primary relative to ground. i.e. with a grounded scope or meter.
Make sure your leads are up to the insulation voltage.
With high voltage, an arc can jump.
Generally, you make probing connections with the power off.
There is always the "one hand in the pocket rule"
The charge on the ignition circuit is usually short-lived.
You do need to discharge HV circuits before working on them. Capacitors on HV circuits CAN sometimes build up a charge AFTER they have been discharged. These are usually large capacitors. They need to be stored with a "keeper" or a short between the terminals.
HV diodes have a very large voltage drop. Possibly 9 or 10 Volts, so the diode test in your meter is worthless. You can still test with a resistor and battery and measure the voltage across the diode.
One system I routinely worked on had a key to open the HV cover. That power supply was capable of 1bout 15 kV at 1.5 Amps. It could obviously do some serious damage. I had an insulated discharge stick. https://www.tomwblack.com/phenix/40400_Discharge_Ground_Sticks.pdf Your not likely to need one of these, but I did and it was much shorter/
Other systems I worked on (100 kV at 0.1 A) X-ray generator and a lamp that required a 40 kV start pulse. Then there were CRT based TV's.
1) One hand in the pocket.
2) Make connections with the supply off.
3) Safely discharge the system.
4) Voltages across some capacitors can return after being discharged.
5) Don't work alone. I did that lots of times.
6) Don't work under the influence or when tired.
7) Safety glasses
In this video it shows a similar board and it's fixing similar part just that the one in my board is another color code and different position this is the YouTube video and the picture of the explanation of the part that he is fixing hope it helps to identify my part, thanks
Many multimeter have a diode scale. They measure the voltage drop across a diode junction up to about 3 Volts.
A Zener diode will basically look like a regular diode because the breakdown voltage is controlled. Breakdown (peak reverse voltage) is non-destructive if current limited.
Schottky diodes have a low forward voltage drop around 0.2 V. Silicon diodes around 0.6. Diodes normally short when they fail. High voltage diodes (think microwave) have a much higher drop. Fast recovery diodes are used when the switching frequency is high. TVS diodes absorb surges and have a large body.
You don't see very many tunnel diodes anymore nor Germanium diodes.
My plasma cutter the problem is aparthy visible burn parts from previous owner not cleaning the tip of the machine toching the metal whit the plasma tip and using same electric braker for compresor, and I will like to fix it I just don't know the part number to buy I already order the 2sk2837 Power MOSFET (in picture) and I just need to find out the value of the switching diode mini- MELF (in picture I already remove the 2 burn ones) so I can serch online electric stores and hopefully buy them to test the machine
The MOSFET has a lead spacing of 5.46 mm. A standard DIP 0.1" or 2.54 mm.
You just need to take a picture with something of a known size in it, in about the same plane as the part and measure th distance photographically on your screen. If I needed a small reference a piece of wire could would. i.e. 22 AWG
You could even use a dime if you had to.
being .705 inches (17.91 mm) in diameter and .053 inches (1.35 mm) in thickness.