Fritz had me remove the 22v zener in the over voltage protection circuit. The cap was then able to charge to 20 volts. It did work very hard from 18 to 20v however. Q4 that drives the charging, was working far harder than usual. So I put the 22v zener back on the board. It seems that the zener limited the cap’s voltage to a perfect level. The zener has a suffix on the part number that shows it’s actually a 20.5v zener. Each voltage has 4 different levels. Mine was the lowest end of the 22v range. Fritz said I needed a full 3 farad cap in order to get to 20v. Mine only tested to 1.6 farad. It’s an audio cap rated at 4.0 farad. Why is it that audio stuff is always playing a numbers game with their ratings?

So now I have some new lower value resistors that I’ve tested on the discharge side of the spot welder. I really like the responsiveness of these resistors. But the voltage regulation has become twitchy. A bunch of mounting and fabrication of parts is all that hold back getting this spot welder finished.

Also ordered a foot switch recommended by Fritz.

Just did a light test on the fet board. First I powered it up. Then attached an ohm meter across the fets. When activated, the meter read close to zero. Good sign. Next I went and added a power supply at 12 volts, but current limited to 3 amps. Went fine. With light duty testing it seems to work. Looks like the next step is to connect it to the output of the control board and somehow simulate the load of a weld being made. The large 4 farad cap is just connected with jumpers. Nothing that can move much current. So we’ll see how that works for testing.

Still lots of machining to do. Still need to get the front panel layout designed and then machined. I still don’t have a clue how to mount it yet. The bar and round stock of copper arrived. So the welding probes need to be machined as well.

Last night until late and all day today I worked on the spot welder. Last night the ac wiring was routed and installed. Today was debug day. I found some issues that needed some help from Fritz. We exchanged a lot of emails. I suggested we open a Yahoo group to better support his efforts. Right now the welder won’t charge the main cap past 17-18v. It should hit 20v. Fritz suggested that D4 was bad. I replaced it to no avail. He suggested I check for solder issues. I re-soldered the whole board to no avail. That’s where the welder sits.

I made a list of other things that need to get done so the project doesn’t stall.

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