Two Hene tubes run off one power supply without damage?

[Alshere]

The subject says it all. Can you run two HeNe's off one power supply and have them last. I know it will work I have 2 Siemens LGR 7641 tubes roughly 1.2 MW output and a brick power supply rated at 2400 volts dc and 6.5 ma.

Taking a mW reading on each tube before and after I see a .1 mW reduction(average) on the tube at the (cathode) end of the series circuit. A single resistor is used.

According to Sam's FAQ laser output power is a fair indication the tube power requirements are in range. I have the right power supply rated at 1.6 to 2.0 kvdc and 6.0 ma or at least it should be "in range" for a single tube I used to get a baseline of mw output. Also I think they are fairly tolerant of power ranges?

I have a digital mm but lack anyway to safely measure hv. Or if I have the way I do not have the knowledge.

So will this take out the power supply, significantly reduce tube life?

A better test procedure?
Things to consider?

Anyway looking at making a lamp using the heat to turn a basic lumia wheel at the top and I want to keep the number of power supplies down so double up. Triple possible?? .

Anyway Thank you in advance

 

[Laser_Ben]

No, it is not a good idea, just use 2 power supplies. It can damage the starter.

 

[photonaholic]

No, it is not a good idea, just use 2 power supplies. It can damage the starter.

Just one of the many reasons I always read Ben's posts.

I figured, rather I just somehow knew this was a bad idea, I just could not explain why.......

Using anything outside it's engineered parameters is not a good idea.

It's kinda like trying to shoot 20 gauge shells from a 12 gauge shotgun, bad idea. Sure with enough tape you could make the shell fit the chamber, but is it going to perform as expected? most likely not.

 

[Alshere]

Thanks Ben. I kinda thought that would be the answer. Time to get another base.

Al

 

[HIMNL9]

It's cause He-Ne psu is planned for give a high voltage at a low current when the tube is not turned on, and then, when the plasma start, reduce the voltage and increase the current for make it work in the right range ..... probably, if you use 2 tubes in series, they don't lase (not trigger), and if you try in parallel, the first one that trigger, just block the higher voltage, so the second one never trigger .....

 

[Bluefan]

In series may work if the trigger pulse can start both, but this is experimental ground, and you can easily blow a few psu's in the process.

 

[Alshere]

Well they do fire.

Yes they are in series. My thoughts are if if one tube fired and stayed lit they both would. Otherwise you would not have a complete circuit.

I can post a pic as soon as I find my card reader. Like I said they put out roughly the same mW lasing as when the power supply that is sized for the tube. Sam's references that is a rough way to tell if it is getting the right voltage/amp but not the recommended way.

The only question was will it fry the brick and/or shorten the tube life. Seems to be the case, but an old time TV tech said it should be fine. He has also offered to measure the voltage and amps for me. He did make sure I was using a fuse with all my tubes but that is a no brainier.

I think I will let him test it and see what it reads. All knowledge is good and I have three of the same supply. Three of the same tubes for that matter.

I will post back when I get a chance to have them tested. My testing is on hold for now..

 

[HIMNL9]

If they works in serie, then you have a PSU with a damn high trigger level at output

Means, usually bricks PSU are planned for lit up tubes with a specific trigger threshold, and theorically 2 tubes in series have a threshold too high for first start ..... ofcourse, when the first lit up, the second get all the voltage and lit up also, the strange thing is that the triggering pulse is high enough for lit up both them ..... or you are using a more powerful PSU ? ..... like, 5 or 10mW psu for a pair of 2mW tubes ?

When i tried with 2 5mW tubes and a 5mW PSU, they've just not lit up .....

 

[Alshere]

Hey HIMNL9

Yes I put that in the original post but probably wasn't clear enough. The power supply I used is rated at 2400 volts dc and 6.5 ma.

My idea was to duplicate the tube length to some extent and allow for the resistor. So a bit under twice the "current?" into two tubes with a combined length 3 inches longer than the tube the power suppy is rated for. Allowing for the narrower bore.


Any thoughts, warnings etc...

Also here is the pic. I took when I had them going.

 

[Solonar]

An example of some HeNe PSU's

The small PSU on the bottom is rated at 1300-2600 V @ 6.5mA The tube above it is the largest it will light.

The middle PSU is rated at 2800V @ 5.5 - 7.5 mA its the only PSU I have that will ignite the big tube.

The big PSU on top is rated at 5 - 12.5kV @ 4-10 mA. Its actually 1 of a pair used for a small 10W waveguide Co2

Since series voltages are additive a PSU like this might work.

 

[Bluefan]

Just make sure everything adds up (or not) correctly. HeNe power supplies are current sources, make sure the power supply has a proper current set for the tube, this current set is the same as a single tube would have, we're in series here, current doesn't change. The voltage doesn add up, the psu needs to have the double voltage in it's compliance range. I'm not sure about the trigger voltage, but I really think the double is here needed too.

 

[Cyparagon]

It can damage the starter.

How?

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