Powering a Melles Griot He-Ne tube (05-LHP-401)?

LazyBeam · Dec 16, 2010

I came across a salvaged 1mW polarized 632.8nm He-Ne tube (part number 05-LHP-401). It's still intact in the black enclosure with the two prong connector. Manufacture date Aug 2005. I was told it still lases fine but something about the machine it was used in required a replacement or upgrade He-Ne tube.

What would I need to power such a device?

I got it for free, so I don't want to spend too much powering it.
Any idea how much it's worth assuming it works and is in good shape?

timelablasers · Dec 19, 2010

Hi,
You need a HeNe power supply. Check out ebay. There are heaps of them on there.
Cheers.

Bluefan · Dec 19, 2010

You will need a power supply with the correct or adjustable current and the right compliance voltage. A wrong power supply can damage the laser and/or the power supply.

LazyBeam · Dec 20, 2010

I was kind of hoping ya'll could point to either the right power supply or a set of instructions to build a proper power supply.

Bluefan · Dec 20, 2010

A short search didn't bring up the specs, but you could try to find a similar tube in size, output and polarisation and it will probably have similar specs in voltage and current. Then you can look for a power supply with that specifications.

LazyBeam · Dec 20, 2010

I'm not sure how to measure the tube or how big the tube actualy is... it's in some sort of black alumunim outer enclosure.
I don't think I want to take the outer enclosure apart either.

james1095 · Dec 21, 2010

Are you sure that isn't a -410? I don't see a -401 but that doesn't mean they don't make them. As I recommend to everyone, read the FAQ:

Sam's Laser FAQ - Commercial Unstabilized HeNe Lasers

You probably need between 1.2-1.6kV at 4-5mA. Unless you are experienced with such things, buy a proper power supply brick rather than trying to build one from scratch, small ones on ebay are cheaper than the cost of the parts. The connector is called an Alden connector, the mate for it will be attached to most suitable power supplies. Notice that it is polarized, the tube requires DC current and if wired backwards or run on AC it will be destroyed very quickly by sputtering contaminating the anode end mirror.

This may work if it has a current adjustment pot on the end but it's a 2450V output supply so running such a small tube may strain it a bit. (note the typo in the rating, otherwise it's creating some serious power out of nowhere!)

Laser Drive 20-28 VDC HeNe Helium Neon Power Supply - eBay (item 300443828610 end time Jan-01-11 18:49:36 PST)

james1095 · Dec 21, 2010

LazyBeam said:
I'm not sure how to measure the tube or how big the tube actualy is... it's in some sort of black alumunim outer enclosure.
I don't think I want to take the outer enclosure apart either.

A tube mounted in an aluminum tube is referred to as a head. It also contains the ballast resistor, wiring, and usually a beam shutter.

Don't attempt to remove a tube from a head unless you have to. It's difficult to do without breaking the tube and/or damaging the housing. You can measure the tube in place though, the ends will be within a half inch or so of the ends of the housing.

LazyBeam · Dec 21, 2010

james1095 said:
Are you sure that isn't a -410? I don't see a -401 but that doesn't mean they don't make them. As I recommend to everyone, read the FAQ:

Sam's Laser FAQ - Commercial Unstabilized HeNe Lasers

You probably need between 1.2-1.6kV at 4-5mA. Unless you are experienced with such things, buy a proper power supply brick rather than trying to build one from scratch, small ones on ebay are cheaper than the cost of the parts. The connector is called an Alden connector, the mate for it will be attached to most suitable power supplies. Notice that it is polarized, the tube requires DC current and if wired backwards or run on AC it will be destroyed very quickly by sputtering contaminating the anode end mirror.

This may work if it has a current adjustment pot on the end but it's a 2450V output supply so running such a small tube may strain it a bit. (note the typo in the rating, otherwise it's creating some serious power out of nowhere!)

Laser Drive 20-28 VDC HeNe Helium Neon Power Supply - eBay (item 300443828610 end time Jan-01-11 18:49:36 PST)

Thanks for the tips. Yes I am sure of the part number, below is a pic of the actual tube in question below.

The laser head diameter is about 1.4" in diameter. It's pretty cool if it has the shutter and ballast already installed... I guess that means all I need is the specs and a cheap Ebay power supply. I think I'll call Melles Griot and see what they have to say about specs.

Do you know if a Laser head (in it's housing) is safe to handle when energized?
I know that it can be dangerous to handle a bare laser tube when energized.

james1095 · Dec 21, 2010

Yes, the housing is grounded. That's the point of a laser head, it has everything but the power supply mounted in a convenient enclosure that is safe to handle and convenient to mount. Just plug it into the appropriate power supply and go.

If the power supply is adjustable, you can measure the current on the tube and adjust it to spec. Plug in just the positive (smaller) side of the Alden connector and connect a multimeter set to DC Milliamps between the negative pin and ground on the power supply. Usually the ground wire on the input side is internally connected straight to the ground pin on the output connector. Power it up and adjust the pot until it reads what the tube requires.

The adjustable power bricks are nice, usually they have a range of several mA, and the rating on the label is just what they come preset to.

LazyBeam · Dec 21, 2010

I called Melles Griot... it's a particular product number/laser that is manufactured exclusively for another company (so it won't show up in any typical Melles Griot literature).

It features exceptionally clean linearly-polarized 632.8nm output @ 1mW.
1.070-1.270 kVDC input @ 4.5mA with 8 kVDC starting voltage.

james1095 · Dec 21, 2010

LazyBeam said:
I called Melles Griot... it's a particular product number/laser that is manufactured exclusively for another company (so it won't show up in any typical Melles Griot literature).

It features exceptionally clean linearly-polarized 632.8nm output @ 1mW.
1.070-1.270 kVDC input @ 4.5mA with 8 kVDC starting voltage.

Sounds like any typical .5-1mW HeNe. Just about any HeNe power brick with a rating from 1200 to about 1750VDC that can be set to 4.5mA should work just fine with that. You can get them with either AC line or various low voltage DC inputs. Personally I prefer the AC input PSUs but the DC ones tend to be cheaper. You might be fine as low as 3-3.5mA but don't go much above the rating. Keep a watch on ebay, you should be able to find one for $10-$20 with some patience and a little luck.

LazyBeam · Dec 21, 2010

How does the power supply work...
Does it regulate the voltage itself and the adjsutment is just on the current?
Or dwo two pots control both the kV and mA?

I'll keep an eye out. I want a DC input so that I can make this portable.
My goal is a Li-ion powered HeNe handheld (for presentations).
I'm guessing it will be about 16" long when it's all done - lol.

james1095 · Dec 21, 2010

LazyBeam said:
How does the power supply work...
Does it regulate the voltage itself and the adjsutment is just on the current?
Or dwo two pots control both the kV and mA?

I'll keep an eye out. I want a DC input so that I can make this portable.
My goal is a Li-ion powered HeNe handheld (for presentations).
I'm guessing it will be about 16" long when it's all done - lol.

The power supply regulates the current, letting the voltage float to wherever the tube likes it. Pretty much just like a diode laser, only the voltage is much higher.

The voltage rating on the supply has to be high enough that it can meet what the tube requires and the drop across the ballast resistor. If it isn't high enough, the discharge will flicker or go out and the power supply may overheat because it's running balls out trying to push enough juice through the tube. If the power supply voltage rating is too high though, it will strain the supply as it tries to run low enough to maintain the set current. The acceptable voltage range is called the compliance range and is usually at least several hundred volts.

Not all PSUs have an adjustment pot, but you want one that either does, or is already built to put out 4.5mA. The pot on those that have it is located on the end near where the wires exit and is occasionally covered by a calibration or warranty sticker.

Cyparagon · Dec 22, 2010

If the PSU was constant current, the ballast resistor would have no effect on current. But it does.

james1095 · Dec 22, 2010

Cyparagon said:
If the PSU was constant current, the ballast resistor would have no effect on current. But it does.

The ballast resistor compensates for the negative resistance characteristic of the discharge and allows the power supply to regulate in a stable manner. Without the resistor, it's almost like driving a short circuit and a very small change in drive will cause a very large change in the current and the regulator will oscillate. As long as the resistance is sufficiently high, the ballast resistor doesn't affect the current. Try putting an additional 50K or so in series with the existing ballast resistor and as long as it doesn't drop more than the power supply is capable of delivering it won't affect the current.

I've reverse engineered several commercial HeNe power supplies and designed a few of my own, they are constant current. Have a look at the PSU schematics in Sam's FAQ and you'll see.

Powering a Melles Griot He-Ne tube (05-LHP-401)?

LazyBeam

0

timelablasers

0

Bluefan

0

LazyBeam

0

Bluefan

0

LazyBeam

0

james1095

0

james1095

0

LazyBeam

0

james1095

0

LazyBeam

0

james1095

0

LazyBeam

0

james1095

0

Cyparagon

0

james1095

0

Online statistics

Forum statistics

Share this page