Adding Digital Generators to an Old Analogue TIG Welder

**chy_farm** · Jul 29, 2020, 10:05 PM

Hi mwmkravchenko, shame but I yet did not think of the overshoot. Thank you for your comment. I am glad to hear something informative from you on this if you do not mind.
Chy

**chy_farm** · Jul 29, 2020, 10:10 PM

One more feature I love about this new generator is that this can replace arbitrary legth of AC welding current with DC welding current.
This method is named "MIX TIG" by a domestic manufacturer Panasonic.Co. to their TIG welders.
My old machine is of mid 90's so is actually an older type built by Hitachi Co., which did not have this tool.

Adding Digital Generators to an Old Analogue TIG Welder-digital_mixtig_unit_set_up_-4-.jpeg

Above monitor in the right with yellow marking is for this "MIX TIG" method, showing it generates 2Hz frequency with 80% duty, for AC welding current, so this means 20% is for DC welding current.

Showing a "MIX TIG" wave form of a couple of another setting, 2Hz frequency with 65% duty, 2Hz frequency with 40% duty, either for AC welding, as follows;

Adding Digital Generators to an Old Analogue TIG Welder-digipulse_700hz_20%25_mixtig_2hz_65%25_170a-5a_-2-.jpg

Adding Digital Generators to an Old Analogue TIG Welder-digipulse_800hz_20%25_mixtig_2hz_40%25_150a-5a.jpg

Chy

**chy_farm** · Jul 30, 2020, 03:27 AM

The former wave form I posted above can be illustrated in another way like one below;

Adding Digital Generators to an Old Analogue TIG Welder-digipulse_700hz_20%25_mixtig_2hz_50%25_170a-5a_comp.jpg

Large red rectangle in the right is an enlarged view of the small red rectangle marked in the left. This part shows how the AC welding current with 700Hz pulse runs.

Chy

**chy_farm** · Jul 30, 2020, 04:19 AM

Again a large red rectangle in the right is an enlarged view of the small red rectangle marked in the left, but this is not of AC current.

Adding Digital Generators to an Old Analogue TIG Welder-digipulse_700hz_20%25_mixtig_2hz_65%25_170a-5a_-2-_comp.jpg

Frequencies of the pulses of the two are a tad different, 700Hz for the left, 650Hz for the right. I did not monitored an enlarged view for 700Hz so instead used another but nearly the same view of 650Hz in the place of the true one.
This enlarged part shows how the DC welding current with 650Hz pulse runs.

Chy

**mwmkravchenko** · Jul 30, 2020, 09:44 AM

What I see is a very useful add on circuit. I have no real comments to improve the waveform. If you want to tune the overshoot, generally it is a change in capacitance that will make the most effective difference.

My guess is that is practical use it will have no bad effects on the usefulness of the added functions that you have created for your welder.

**chy_farm** · Jul 30, 2020, 07:01 PM

Good morning mwmkravchenko, will keep your information in mind, thanks.
Chy

**chy_farm** · Jul 31, 2020, 01:46 AM

Originally Posted by chy_farm

As far the schematic, I am thinking of asking a buddy who guides me to attain this job with a lot of information on welding machines if he gives me permission to open his schematic design of this unit.

This buddy gave me OK to open his schematics on this project, will compile a bit and post here soon.
(Note he says the schematics are only for Hitachi's welder, version name 'ADGP' and some series after this. )

**nova_robotics** · Jul 31, 2020, 02:17 PM

Another great project. Well done. I love hacking old things to make them better.

When I was in high school I bought my first welder. There were two options when I bought it. I could have the 70 amp welder, or for more money (that I didn't have) I could buy the 90 amp welder. I bought the 70 amp. The 70 amp and 90 amp looked identical in the store. After using it for a while I noticed a different set of screw holes on the bottom of the machine. I noticed that the isolation plate between the primary and secondary on the transformer wouldn't come out all the way. All that needed to be done to gain the extra 20 amps was unscrewing the transformer, moving it over to the other screw holes, and putting it back together. It was a 30 minute job.

Your welder hack is obviously way more impressive. Keep up the good work and thank you for sharing. You should consider putting up a Github page.

**chy_farm** · Jul 31, 2020, 05:58 PM

Originally Posted by nova_robotics

---------
When I was in high school I bought my first welder. There were two options when I bought it. I could have the 70 amp welder, or for more money (that I didn't have) I could buy the 90 amp welder. I bought the 70 amp. The 70 amp and 90 amp looked identical in the store. After using it for a while I noticed a different set of screw holes on the bottom of the machine. I noticed that the isolation plate between the primary and secondary on the transformer wouldn't come out all the way. All that needed to be done to gain the extra 20 amps was unscrewing the transformer, moving it over to the other screw holes, and putting it back together. It was a 30 minute job.

----------- You should consider putting up a Github page.

Good morning Nova, thanks. I'v been thinking of Github too, where I have an account too.

This welding thing happened to you is funny, you did a good job!

Chy

**chy_farm** · Aug 1, 2020, 09:04 PM

A result of this retrofit, tried angle-butt-welding with 0.5mm steel sheets by using 800Hz pulse, with setting of welding current 100A, base current 5A.

Adding Digital Generators to an Old Analogue TIG Welder-steel_0.5mm_800hz_100a_5a_03.jpg

I think I did it better than ever as a green hand.

Good feature to me is that the arc does not wonder, may be because both the welding current and pulse frequency are high.

Chy