Adding Digital Generators to an Old Analogue TIG Welder

[jdurand]

Take it easy mate, the generator-band to be applied to this old welder is not so high, only 0Hz to at maximum not over 1kHz, they dont do any harm to the primary inverter board.
Chy

I just wanted to warn that trying to duplicate an old circuit with modern chips can lead to unexpected problems. If you don't know about the speed change it can be very confusing to you. I had to go through some old product designs done by another engineer and replace all the circuits like the above with stable ones. Where possible I used digital timing so it's exactly the same every time, but at least using parts with known Schmidt trigger inputs or analog parts makes one happier at the end of the day.

Because of that same issue, I started adding an extra resistor to all my crystal oscillator circuits. The old design started randomly jumping to third overtone which isn't at all what was intended.