Valid Arc Lost 2

Hi All,

I know there is a couple of threads now about this same topic but mines slightly different.

I have an everlast 50s plasma cutter that keeps losing valid arc.

On mode 0 I could get an ark ok, but half the time it would work as it should and the other times it would pierce (torch on), stop (torch off), start moving about the cut path, wait about 1 second and then pierce and continue cutting (torch on).

So I have moved to mode 1 but now I cannot get a valida arc at all. I wonder if the oxide on the relays has built up like Rod suggests in another topic, but I do have the 1k 1W resistor like he suggests.

This is how it is wired up, does anyone see anything wrong?



Note I have had the GND wired to both the DC power supply and the field power ground on the mesaboad but this makes no difference.

Is my resistor in the right spot?

Thanks for any help

For mode 1 when using the relay it doesnt operate, it has a small LED that would come on. My torch on relay works fine and I swapped them over and the torch on relay still works so I know its not a faulty relay.

That wiring is different to how I did my Everlast ArcOK. I did not use the intermediate relay. I wonder if its causing the problem? Try bypassing the relay, connect pin 9 direct to the input pin. Then put your 1k resistor from the input to Ground. Try cycling it a few times and see if it improves.

Also check that the resistor has not burnt out. (remove one end and test for resistance across it).

I'll see if I can discuss the 1k value with my panel guys. I'm not sure if the revised 90 ohm resistance will be better or worse without doing some sums.

I thought I'd saved the relay part number but I didn't. You can find it and read the number if you trace the wires back from the Circular connector inside the everlast. Worst case you can replace the relay.

rodw wrote:

That wiring is different to how I did my Everlast ArcOK. I did not use the intermediate relay. I wonder if its causing the problem? Try bypassing the relay, connect pin 9 direct to the input pin. Then put your 1k resistor from the input to Ground.

ohhh okay thanks.

So don't use that relay at all?

Asnd where does Pin 10 go, still to +24V?

Thank you Phil.

So would look something like this?

little_sparky wrote:

Thank you Phil.

So would look something like this?

Looks perfect. I visited Chris, one of my advisory panel on the way home just for you. This would be a good test. The 1k resistor only puts 24 mA through the relay so its still under the minimum current specification. This must have been enough to get it working in the beginning but its failed again as more oxide built up.

So be a good Sparky and duck into Jaycar in the morning and grab 3 x 270 Ohm 5W ceramic resistors. Replace the 1k resistor with these wired in parallel and that nasty oxide won't know what hit it when 267 mA goes through the relay. Hopefully after a few cycles, it will have burnt through the oxide and be working reliably again!