Mma, liftarc and hf.
Some machines ignited on dc+ to heat the tungsten.
When dc+ rail broke than the control can get confused.
You're right, I just measured the open voltage to 71 volts dc, and 21 volts in HF mode. Both on the dc block and the ac block. So something is wrong.It is corrrect. The DTD start by ac welding always with the + on the torch. After the welding current starts the ac mode is activated. If you don"t have the full bridge then the open voltage is to low and the HF will not start. So switch of the HF. Select the DC mode in Tig. and measure the open voltage after you activated the torch switch. You shout measure a voltage of around 90 volts dc. If it is much lower you have a problem in the DC or the AC block.
I went back to the welder today, and measured the voltage without the ac block on. Dc out around 90 Vdc, but only 20 Vdc in HF mode.If the voltage is to low the electronics think that you are welding and at that point you don't need the HF. you have to find out what is wrong. If you disconnect the welding cables betwen the dc and the ac block. Then measure de open volltage output of the dc block again.
Ok, thanks. So the 3 i parallel are 3 x 100 k?Resistor 431 is 100K
The formula for those 3 resistors in parallel is:Ok, thanks. So the 3 i parallel are 3 x 100 k?
Seems like the dc block i okay, i can weld in dc mode without HF. The psu on komm pcb is ok, it makes - 19 vdc on the lm7915 and -15 Vdc out of regulator.Please disconnect the DC block from the AC block and measure the output of the DC block. It must be possible to weld on these two cable comming out of the DC block.
I have an old picture with adviche to change some parts.