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I am drawing a schematic circuit for the pro tig 200. I have finished the control board output section and starting on the main power board.The unit I have is not outputting a signal to start the PWM IC that runs the weld power mosfets. The signal I need measured is on the control board (which only display/control panel needs to be opened not welders case). The ribbon cable has +15v on one end (pins 1-4) and ground on the other end (pins 28-34). The pins in between are used as inputs to the MCU and outputs from the MCU. The ribbon cable pins are doubled up per signal. Signal pins are 5-6 are together, 7-8, 9-10, 11-12,13-14,15-16, 17-18, 19-20, 21-22,23-24,25-26 . Each set is soldered together. I need a waveform reading of pins 5-6 in stick mode from min to max, or a voltage reading @min then @ max. The output I have from my bad unit is under 2v which I think is way low from a +15v powered IC, but without a good reading I am not sure. With a running unit waveforms can be obtained as to what should be expected at the inputs and outputs. This info will make repairing these units easy. When you know what is a normal reading, finding what is not functioning is much faster.The low voltage power section is run by a standalone PWM driver and is working, +15v -15V and 18vdc. This supplies the control board power.The top PCB with the power mosfets that supply the welding board is not getting the signal to make welding power.This setup is similar to other brand dc-dc switched welders that use a common driven transformer that drives the 4 mosfets channels that make the welding power.Problem is not a big one as the circuits are not working cuz they are not told to work. Thus the control board signals come into play, I need to eliminate the control board as the problem. The output signals readings from a working control board will be needed to confirm the control board is bad.If anyone with a protig200 could take a few voltage readings or even better some waveform pics of the outputs from the control board would be of great help. The welder is a good design from several welders that I have repaired over the years. The failure is not a burnt out part or bad design. It appears to be a internal component failure, which could happen to any electronic device. I will post schematics when done.Unit has a very thick sealant in the top PCB, way thicker then any Miller, Hobart, Lincoln, Thermal Dynamics, or ESAB unit I have ever opened to repair. So far all IC chips are off the shelf, except the MCU which is a renasas rc8/2b which will have an internal program running it, which would have to be dumped from a good MCU to program a new one.Not sure if anyone has the desire to get me the info, or the oscilloscope/ volt meter to take a few measurements and post the results.If I get the unit up and running I will post info with wave forms which will remove harbor freight from the only source for repair info.Unit design looks very promising.ThxLast edited by Hard_ware; 11-02-2019 at 07:19 PM. |
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发表于 2021-9-1 23:17:07