Sunday, May 31, 2009

Making Progress

I'd like to thank eBay's motorcycleman561 for opening up his plasma cutter and sending me his resistor values. My plasma cutter is a CUT40 and his is a CUT40D, but the resistors seem to be the same!

I ordered a 10W 1kohm resistor (colors Brown, Black, Red, precision Gold). The plasma cutter initially had a resistor of 5W 1kohm, but since it burned out, I'm replacing it with one that can handle double the power...

The results:

The plasma cutter still doesn't work... The resistor gets very hot (270F) when the trigger is held down.

Here's the new resistor:



Installed:


Wednesday, May 27, 2009

CUT40 Plasma Cutter

I'm creating this blog for two reasons:

1. To hopefully repair my plasma cutter.
2. To help others repair their plasma cutter if it has the same problem as mine.

I have a LOTOS CUT40 plasma cutter, but I'm sure that many other models are very similar, if not identical. Other similar units may include CUT40D, CUT50, CUT50D or Simadre CUT40, etc.

I opened up the plasma cutter and found a burned out resistor on the bottom transformer/rectifier circuit board. The circuit board consists of four large capacitors, a transformer, some rectifier diodes, some resistors and connectors.

I wouldn't be writing this except that before the resistor burned out, it appears to have gotten extremely hot and the resistor color bands burned off, so I can't see what value I need to order. I could make a guess or calculate the value, but I thought that I would ask you if anyone would consider opening up their unit and tell me the color band colors?

I have attached some pictures to show exactly which resistor it is. The resistor is about 1" long, 1/4" thick, gray in color, and it appears that the second band from the left is black.


If anyone has the time to open up their unit and let me know what the colors are on the resistor, I would be extremely grateful.

Thank you for your time, and if anyone needs help repairing their plasma cutter, let me know!


Pictures

The plasma cutter:


A top view with the case removed:



A side view to show the orientation of the next pictures:



Zoomed in on the location of the rectifier circuit and three resistors including the bottom burned out one:



The burned out resistor:

The color band goes from left to right in the photo below. In-case another unit's resistor is oriented opposite, the color band ends with the color that is slightly separated, ie. gold for the top resistor. The gold band is often silver and shows the precision of the resistor.
Eg: The top resistor has the colors: Brown, Green, Black, Orange, and precision Gold.




The burned out resistor removed:

What's this part for?

If anyone has any idea what the circled electrical part is, I'd love to know. There are two metal bars sticking up, separated by about 1/16", and each bar has a circular copper piece near the end. It appears to be some sort of contact, but I've never seen one before...