Experimentonomen´s first argon.

[Experimentonomen]

A schematic of my current trip circuit:

[shrad]

I think mechanical delay from the relay plus signal propagation time along the opamp and interlock lines would still be more than what it takes for a fast-blown fuse to blow, but I may be wrong

especially, does your overcurrent switch off the tube or power transformer directly with that relay (I don't see so)? or does it take place later on the interlock chain?

it might be worth investigation, as a blown tube would be something irreversible (and I find what you do worth of interest, I would be sad if you blew your tube)

[Experimentonomen]

Anyone up for a video of the regulator in action ?

[shrad]

great! keep the good work! it will surely help people to build homemade supplies!

[Experimentonomen]

Ignitor issue resolved.

[Experimentonomen]

FILAMENT ISSUES!!!

As im using a big 1500VA transformer i cant get the filament voltage of 3V, if i use 3 turns i only get 2V under load and add a single turn and im at 3.3V which i think is too high.

For the winding i use two mainds installation wires in parallel, if i disconnect one i get 3V but then the winding gets hot instead.

Now this test was without the tube cirrent so with that on the transformer, maybe the filament volts will drop to around 3V during operation.

I know that too low filament voltage will fry the tube within hours or even minutes and too much will cook off the coating on the filament.

I see in the schematic of the SP262A psu that the filament transformer is specced 3.5V and 19A but im pretty sure the filament voltage and current vary between models.

[shrad]

A solution would perhaps be to use a 3,3V switching power supply with voltage adjust and sufficient current output (they are pretty cheap, like $70). A +/- Rsense connection is also worth as with a single opamp you can set up a current regulation easily

For big transformers as the one you are using, I think I remember of a technique which consisted of playing with some reverse wirings on order to substract some voltage, but it might also result in a smelly barbecue

I don't remember, is it AC or DC?

[mixedgas]

Microwave oven transformers. Knock off the copper with a hacksaw and cold chisel...
If not, I can sell you a cathode transformer cheap, but the shipping is ARGHH!!! expensive between here and Europe. Remember to center tap it to balence the load off the cathode.

standard laser ion cathodes are 2.65V and 3.2 V, I've NEVER seen anything else... Since there are only 2 or 3 companies that make that kind of emitter, its pretty much standardized.

Steve

[mixedgas]

A solution would perhaps be to use a 3,3V switching power supply with voltage adjust and sufficient current output (they are pretty cheap, like $70). A +/- Rsense connection is also worth as with a single opamp you can set up a current regulation easily

For big transformers as the one you are using, I think I remember of a technique which consisted of playing with some reverse wirings on order to substract some voltage, but it might also result in a smelly barbecue

I don't remember, is it AC or DC?

If he uses DC, he needs to reverse it about 5-10 times a second with a H Bridge to balence the plasma on the cathode. Its done for ultra low noise lasers that cant have a .1 % 60 hz spike in their output. Otherwise DC kills em fast.

Steve

[Experimentonomen]

I use AC with a centertap.