Hi there!
I have this high frequency industrial welder on my bench which somebody tried to repair before I got it.
It had three missing chopper IGBTs, and only one shorted out was still soldered to the main PCB. Thanks to this I was able to identify these as IGBTs. All four IGBTs gate resistor sets were open, and one set was visibly burnt along with PCB under them. I have a few questions for the experienced ones.
1. There is only one transformer for all four IGBTs gates. I tested all four windings driving the gates and they seem ok. However, I noticed a silicone-like glue on the PCB between these gate circuits. What type of insulating paste is this? I remember the old PS/2 IBM monitors developed problems because glue became conductive over the years.
2. Has anybody developed a way to test chopper gate drive circuits without the chopper transistors to make sure gate signals are ok and won't cause transistors to turn on at the wrong time?
3. If anybody is familiar with this welder, there seems to be a missing component marked as either U1 or V1 between the rectifier's DC + and one AC input terminals (this unit operates on both 120V/220V sources automatically). Does anybody have a detailed schematic of this welder's section?
Thanks in advance for any help you may provide.
Rafael
I have this high frequency industrial welder on my bench which somebody tried to repair before I got it.
It had three missing chopper IGBTs, and only one shorted out was still soldered to the main PCB. Thanks to this I was able to identify these as IGBTs. All four IGBTs gate resistor sets were open, and one set was visibly burnt along with PCB under them. I have a few questions for the experienced ones.
1. There is only one transformer for all four IGBTs gates. I tested all four windings driving the gates and they seem ok. However, I noticed a silicone-like glue on the PCB between these gate circuits. What type of insulating paste is this? I remember the old PS/2 IBM monitors developed problems because glue became conductive over the years.
2. Has anybody developed a way to test chopper gate drive circuits without the chopper transistors to make sure gate signals are ok and won't cause transistors to turn on at the wrong time?
3. If anybody is familiar with this welder, there seems to be a missing component marked as either U1 or V1 between the rectifier's DC + and one AC input terminals (this unit operates on both 120V/220V sources automatically). Does anybody have a detailed schematic of this welder's section?
Thanks in advance for any help you may provide.
Rafael
