Powermax 600 help needed

[denverguy]

Hello,

I'm new to the forum and have been lurking a bit but now have a question. I have an 16-year-old Powermax 600 that will initially fire but after one or two cuts, will not fire. After working with Hypertherm support, I have, unfortunatley, narrowed the issue down to the power board. In doing some resistance/continuity checks on the board, I have found an open resistor which I plan to replace but the numbers are burned off the sides.

I'm hoping that someone would be kind enough to post a picture of the markings on the side of the resistors. Maybe you haven't cleaned the inside of your unit in some time and it's due for a spring cleaning?

There is a pair of vertically mounted white ceramic resistors and they are labeled R48 and R49 in the attached photo.


If anyone has already replaced and sourced these or found that another component is bad and caused the resistor to blow, I'd love to hear what you found.

Thanks in advance

[denverguy]

I needed a working plasma for this weekend so I took my best SWAG at the specs and ordered some new resistors. I installed them today, let the unit run for about 20 minutes and cut about 15 feet of 3/8" with maybe 30 stop/starts, the unit didn't skip a beat.

For anyone that diagnosis a bad power board (LED 7) I highly recommend checking resistance values on resistors R48 and R49, it's a $10 fix versus a new board. Total time for the repair was about an hour to remove, replace the components and reinstall the board. Researching the problem and finding the components took a few hours.

I initially noticed that one of the resistors was ambient temperature and the other hot using my infrared thermometer. I then checked the resistance with the components still on the board. I believe these are capacitor bleed resistors so you will get some odd values but you should expect to see similar values. In my case, R48 read 3.279K Ohms, R49 read 3.88M Ohms. After cutting them off the board, R48 read 4.17K Ohms and R49 was open.

Based on the physical size of the original resistors, I believe they are 10W resistors, I could also make out "4K" on the board but not what followed. I wasn't able to find an exact match and ended up installing Ohmite Series 20 4K Ohm 10W resistors, part number 20J4K0E, they are not ceramic potted, however. The original ceramics had a standoff to protect the PCB, I made sure that Ohmites had significant clearance from the board. 4K Ohms was the closest that I could find to the 4.17K Ohms measured on the working resistor.

The Ohmites run hot, they peaked at just under 200c. The documentation seems to imply that it's in an acceptable range but I don't have a compare nor am I an expert here. I'd still appreciate if someone could post the resistor specs next time they have the hood off.