HeNe Troubles :( HALP ME!!!!

hey guys!

I have been wanting to get into gas, so i bought a 3.4mw 543nm HeNe off of hwang21.

The tube needs 2800v @ 6.5 ma

So i bought a DJT-28-00 PSU

2600 - 3200v

>10kv startup

I set everything up like this:



The PSU has a built in 5 second delay, so i plug it in, wait five seconds

and i hear a soft *click* presumably the startup voltage.

Then, nothing..... The tube doesn't flicker or anything!

Any way i can test it or GET IT TO WORK PLS?

Thanks
-Matt

If you have a plasma globe you can hold the tube up to it to see if it's still good.

Those head end caps have ballast resistors in them, remove the resistor you have on the cathode (aluminium can side). Ballast resistances go on the anode side only, btw.

Sigurthr said:

Those head end caps have ballast resistors in them, remove the resistor you have on the cathode (aluminium can side). Ballast resistances go on the anode side only, btw.

Click to expand...

not necessarily. alot of bigger tubes have them at both ends. But the bulk needs to be at the anode end. bear in mind most tubes do start up right away, but some do take a few moments to spring to life. I once had one that took almost a full 15-20 seconds to start!

if you have a proper power supply, which it sounds like you do, then make sure you have the ballast within 3 inches of the anode. Its very important. if you run it once and it doesn't light. turn it off, then carefully unplug the alden and short the pins on something metallic. if you get a loud snap, then likely the voltage is working, if not, you have a short somewhere.

If you want an easy way to check the tube, (and it fits, this one might not) put it in the microwave. Take a full glass of water (for load balance, very important) and put the tube in the microwave for about 5-10 seconds on a fairly low power (so you don't damage or cook the tube) I usually do pwr [7] on mine. if the tube is good it should light up all over as the gas gets energy from the microwaves. just don't leave it in for very long or you'll cook the tube. do it in short few second pulses on a moderately high power. even if the tube is bad, but still retaining its gas it'll light. I have an old softseal REO tube i can excite this way. it's up to air so it lights a dull purple, instead of the normal color. but if it is intact it should light up.

Check your wiring as well. you might have a bad connection somewhere, if you have exposed metal/solder joints then you can tend to get alot of arcing. HV has an easy time getting away, so make sure you have everything insulated properly. make sure all your solder joints are clean and solid and covered...also never solder to the tube, always do it to a clip, then clip to the anode groove. and make cure the contact is nice and snug. Try not to do it near the mirror, and as close to the glass envelope as possible. What are you using to power the power supply brick? is it AC? or DC?

The DC ones will need at least 12V @ 3A to work right. I'm using a Laser Drive 180T-2800-6.5-TTL-5

if you get flashes, then the current is likely too low. if the pot on your power supply isn't calibrated, you may have to turn it up. pot range on these is typically 4-7mA usually clockwise is to turn the current up, and counter-clockwise is to reduce it.

If you want i'm on skype and can help you. just click on the symbol in my profile bar.

What happens if you run the tube with no resistors?

One time i turned it on i heard some sizzling

what does that mean?

Sizzling could be the tube half on. I've had that problem before. Tube needed more voltage.

IIRC the ballast resistor is to limit the current going to the tube when the gas ionizes.

Sweg



My first gas laser in person

YAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAS

ARG said:

Sizzling could be the tube half on. I've had that problem before. Tube needed more voltage.

IIRC the ballast resistor is to limit the current going to the tube when the gas ionizes.

Click to expand...

its usually HV leakage.


anyway....glad I could help....looks like you just had a short. Enjoy your new first gas laser get a pair of V blocks and find a nice place to set it up and admire it Now you'll be hooked and wanna collect em all!

Glad you got it working!

@UK I never liked the dual resistor design because it shifts the cathode voltage in reference to ground. When housing is grounded it creates potential arc points. I only had one head with this setup and it looked like a repair job, so I assumed it wasn't a standard feature. Electrically I don't see a reason why it would be necessary over a single anode resistor.

Btw the ballast is to compensate for the negative resistance a plasma channel presents. There is always a voltage drop across it though whenever current is flowing.

Sigurthr said:

Glad you got it working!

@UK I never liked the dual resistor design because it shifts the cathode voltage in reference to ground. When housing is grounded it creates potential arc points. I only had one head with this setup and it looked like a repair job, so I assumed it wasn't a standard feature. Electrically I don't see a reason why it would be necessary over a single anode resistor.

Btw the ballast is to compensate for the negative resistance a plasma channel presents. There is always a voltage drop across it though whenever current is flowing.

Click to expand...

It helps with the stability supposedly, and I think it balances the heat and resistance load on the tube and it reduces noise in the beam I think. I do know there are a couple minor reasons for it, but i'm not 100% positive on it.

Sigurthr said:

Btw the ballast is to compensate for the negative resistance a plasma channel presents. There is always a voltage drop across it though whenever current is flowing.

Click to expand...

Negative resistance? As in a resistance with real and imaginary parts or something else?

Negative resistance is when the more current you apply the lower the voltage drop across the conductor becomes.

Im think i'm catching the gas (laser) bug.

How long can you run these continuously? (duty cycle )

KRNAZNBOY said:

Im think i'm catching the gas (laser) bug.

How long can you run these continuously? (duty cycle )

Click to expand...

I have never heard of a duty cycle on these personally. I would imagine your limiting factor will be the PSU so just pay attention to it and if it gets hot turn it off. The laser itself shouldn't get too hot I don't think.

the reverse resistance from the plasma and cathode discharge. sorry I worded it wrong. but no there's no duty cycle. they run continuously on air. warmup is usually 20 min suggested for most tubes. but usually 75K ohms at the anode end only is enough for most tubes.

Wait, this happened yesterday and now its happening this morning too.

The tube light fine, every time, but no laser?

I can see the lasing INSIDE the bore, but no output AFAIK

Do i just need to let it warm up, or is something mis-aligned?

EDIT: Uh-oh, when i shake it (not violently) i will see it lase for short intervals (as it is temporarily aligned...)

:wtf: HALP