Uniphase 2213 doesn't start

Dear Laserfreaks out there :yh:

It's been a while since I posted last time here.
Now I come up with a starting problem regarding a jdsu uniphase 2213 argon laser.

I bought this tube for little money, without power supply or cooling unit. At first, I thought to test the tube just with a very simpel pulse circuit, because I have no cooling fan yet, as discribed on sam's laser repair. I heated up the filament with 3V / 15A. Then I charged up a 100µF/400V capacitor to about 150 to 160V for providing the anode voltage for a short pulse. Then I gave 12V to start + and start - terminals on the head (violett and green wire). The igniter pulses can be heard, but the tube doesn't flash and there is no current flowing through the tube. I checked a few things:
Filament is okay and doesn't hang into the beam.
I hooked up a HeNe power supply to the tube to check if the tube didn't come up to athmospheric pressure. There was a violett/pink gas discharge visible, so I think, the tube should not be leaky. Then I checked, if the anode voltage can be measured directly across the tube, voltage was present. I then hooked up the tube to my selfmade ion laser power supply but it didn't start, I provided 150 to 170V anode voltage and tried with tube currents between 4 and 7A. There was never flowing any tube current. I then tried to measure the HV-peaks from the igniter, although I could hear the pulses. I hooked up a HV-probe with Scope to the tube. Igniter pulses were around 15kV and occured about twice a second, but actually the highvoltage probe I used is normally intented for measuring 50Hz and DC, no high frequency pulses, so I'm not quite sure, if the results are okay. The pulses were very short and there was no ringing, just very short spikes. I suspect that the igniter could be the problem, but it could also be the tube itself.

What do you argon laser specialists out there think about the failure? Could it be that the igniter hv-transformer has a shorted winding or something like that?

Any help or hint or schematic is very much appreciated! :beer:
Thanks for reading this and a nice weekend
argon

Hold a white card in front of the tube when the ignitor is firing and see if you have a pulse.

You really need about 300V across the tube open circuit to aide in starting, plus the ignite pulse.

You need enough energy stored in your capacitor in your pulser to transition from glow discharge to arc. You may not have enough.

Saying do not look down the bore when pulsing the tube should be obvious.

Steve

Dear LSRFAQ

Thank you very much for your answer.

Hold a white card in front of the tube when the ignitor is firing and see if you have a pulse.

Click to expand...

I did this, but there was basolutely no pulse and there was no current pulse flowing through the tube as well.

You really need about 300V across the tube open circuit to aide in starting, plus the ignite pulse.

Click to expand...

300V? I thought, it would be okay to have a bit more than the anode voltage (which is about 140V for this tube if I'm right) plus the igniter pulse.

You need enough energy stored in your capacitor in your pulser to transition from glow discharge to arc. You may not have enough.

Click to expand...

Yes, I am aware of that. I suspect the ignition circuit, but it is difficult to say where the problem really lies. Probably I will try to ignit the tube with another igniter circuit than the original one.

Regards
argon

It might be rated for 140V, but it's likely been sitting for a while. That tends to raise it.
Of the power supplies I'm aware of, the open-circuit voltage is about two times what the running voltage is.

It might be rated for 140V, but it's likely been sitting for a while. That tends to raise it.

Click to expand...

Okay.

Of the power supplies I'm aware of, the open-circuit voltage is about two times what the running voltage is.

Click to expand...

Two times? That would mean, that half of the voltage would drop on the power supply (if it is a linear supply), so there would be 140V * 10A = 1400W(!) wasted in the supply in the worst case!

With my selfmade ALC-60X supply and the ALC-60X head I can supply the circuit with just 10V above anode voltage and it still works fine. This saves a lot of power and the supply stays cool.

I tried now to start the tube with a selfmade igniter. Made a ferrit transformer with 2 windings primary and about 40 windings secondary and discharged a capacitor with 47µF / 350V through the primary. Unfortunately this didn't help. No current peak and no laser pulse.

Next I will raise the anode voltage, but no more than 200V. I will inform again what the results are, but I'm afraid that it will not work. It seems to be something wrong with this tube. :cryyy:

Best regards
argon

Wouldn't a coil with a 40/2 ratio in windings only up the voltage 20x? A 350x20=7kV start pulse doesn't sound as much.

Yes, indeed. Maybe I should try again with 1:80 turns ratio, as it is described in sam's laserfaq. But I know that little argon tubes can ignit with a 2:40 turns ratio, because the capacitor together with the coil produces a high frequency ringing pulse there, and this is not the same as a DC voltage of 7kV.

Regards hvpower

Open circuit voltage across nearly any tube is ~300 volts, just because open circuit is high and the caps are charged, does not mean the run voltage does not drop down to ~150 volts or so in the PSU.

60X for example charges the ignitor caps to ~600V through a 100K resistor.

Until the electron cloud forms around the cathode, it takes a lot of energy to get a neutral glow to transition to a arc discharge. The cathode also needs another ~25 watts once its lit. Just because your filter caps are charged hot before start does not mean you need more running dissipation in your psu. That start energy needs to come out of a cap bank and the ignitor.


Uniphase is typically a 85 to 95V tube when running, bigger ones draw a bit more, but the supply for the largest 110VAC systems is still 1.5-1.7 kilowatts max off a 110V line. Much above that and most line breakers would snap. 220V tubes such as a 643 could need considerably more. 300-350 mW is about the 110V practical limit, anything larger usually needs 220VAC raw supply.

Steve.

LSRFAQ said:

Open circuit voltage across nearly any tube is ~300 volts, just because open circuit is high and the caps are charged, does not mean the run voltage does not drop down to ~150 volts or so in the PSU.

60X for example charges the ignitor caps to ~600V through a 100K resistor.

Until the electron cloud forms around the cathode, it takes a lot of energy to get a neutral glow to transition to a arc discharge. The cathode also needs another ~25 watts once its lit.


Uniphase is typically a 85 to 95V tube when running, bigger ones draw a bit more, but the 110V supply is still 1.5-1.7 kilowatts max off a 110V line. Much above that and most line breakers would snap.

Steve.

Click to expand...

Just an FYI --

I'm not knowledgeable enough to know if this is a factor, but the 2113 requires the 220V PSU

Peace,
dave

The laser actually fires now at about 180V tube voltage ;-) Unfortunately there is no beam. It seems the internal mirrors are misaligned, but they are part of the tube itself, so it will be very difficult to align them. I actually don't think I will succeed :yabbem:

Regards
argon

Maybe it's an idea to check the alignment to be sure that's the problem. I don't have a small argon to try this, but I'd guess it would be possible to shine a small HeNe down the bore and see if the reflections of the HR and OC line up.

If there's a stable arc but no emission, what other ailment besides alignment is likely?

I'm not very experienced with argons, but gas fill problems and other things may be the problem. But the advantage of using a HeNe is that you see which way it's misaligned, saves you from pushing the wrong way. At least I think it would.