Help wanted - 30 years old HeNe made in Czechoslovakia (Pic heavy)

I have acquired today a pretty old tube (I'm guessing 30 years) with a matching power supply. The problem? It doesn't work. When I turn it on, a green LED turns on in the power supply, and that's everything. No buzzing from the power supply, and since the tube is covered, I can't see if there is any discharge in it. When looking in the aperture, I can't see anything. I have tried taking the supply apart, but I couldn't find anything wrong with it. No expanded caps, corroded resistors, blown fuses, nothing. More in the pictures.

The tube


The whole tube


Front of the tube


Front mirror


Back mirror. I can see my eye there when I'm looking at it.


The warning label. 633nm max 8mW "If the beam hits eye, there is a risk of losing sight."

The power supply and its guts


The power supply. The green LED glows, and that's everything. Oh well. Let's take it apart.


The guts. There is a double line transformer in the back, the part where line voltage is switched on and off is under the black cover with a red bolt on it, and the HV part is in the front, next to the big capacitor. I measured 42V there. There is a fuse next to the power connector, and it's NOT blown.


Ditto, a top view.


The top PCB of the HV part exposed. The big transistor is a Tesla KD503, and there is another fuse, which is NOT blown.


One side of the HV part, when opened up. There are two cap arrays, some rectifier diodes (to form a voltage multiplier, I think), two HV transformers and a HV resistor in the back (more about that in the next picture).


Other side of the HV part, a big HV resistor (they used to put them in glass tubes to prevent them changing value I think) and another set of rectifier diodes.

Unfortunately, I don't have any equipment to measure 3,6kV, I'll try to borrow a probe. I haven't found a way (yet) to take apart the tube to see the discharge or if there's a lose connection somewhere. I'm too scared to unscrew the screws that are in the back.

Does anyone here have any experience with Tesla (tube manufacturer I believe) or Metra Blansko (power supply manufacturer)? I know this forum is mainly American, so there's probably not much info on communist-era things... Still, I would love to get this thing working.

That's an awesome looking HeNe, it definitely needs to be repaired even if it means getting a new tube for it. The psu is quite interesting. Are those lines on the HV resistor actually part of the conductive track? Maybe you should check the glass resistor with a DMM and see if it registers a value.

Does the He-Ne buzz as you try to start it? I know with mine, if I leave it for a while without running it, it buzzes and you can see the plasma dissipate throughout the whole tube.

It also takes a few tries to get it lazing... Since this is a very old unit, I would suggest just keep kicking it with power. Turn on for 5 seconds then off... then on, then off... keep going till it works or you give up.

You could probably zap the tube with a HV source like an oudin coil, plasma ball, neon sign transformer or something similar and see if you get any light from the tube. If it doesn't light up at all with one of those then the tube is toast.

MarioMaster: yes, that's what I was thinking, fix at all costs! I'll probe the glass resistor tomorrow. They say that Metra has a unique design.

Bobhaha: The tube does not buzz, the PSU is buzzing VERY quietly, it's almost impossible to detect. My uncle suggested it might be buzzing in ultrasound.

EDIT: I managed to take off the back of the head, and got to see the tube itself

Still, no glow when I power it up. Plus, the tube seems glued in. Not happy...

Yes. Most of these are "glued" into the housing with silicone

You need to get an HV probe to check if the PSU is putting out voltage (easiest)

Then shoot the tube with an oudin coil to check if the tube is up to air.

Finally, check the internal ballast resistors and connections. They are probably under the other end cap or buried inside some thermal silicone in either of the caps

"Buzzing" in the tube is usually caused by insufficient current/voltage being supplied

Peace,
dave

**EDIT** -- I am assuming you have already checked any connections for continuity, fit, and "dirt"

I'm going to HV probe it on saturday. I checked the connections, and it's continuous all the way from the HV multiplier in PSU to the inside of the metal tube.
Where is the internal ballast again? I don't remember seeing any caps/resistors inside the back of the tube. There is a big resistor in the HV part of the PSU though.
Lastly, how can I make an oudin coil? I know that it is something similar to a tesla coil, but I can't find any clear guides on the internet. I can however borrow a USB plasma ball, would that be enough?

Johnyz said:

I'm going to HV probe it on saturday. I checked the connections, and it's continuous all the way from the HV multiplier in PSU to the inside of the metal tube.
Where is the internal ballast again? I don't remember seeing any caps/resistors inside the back of the tube. There is a big resistor in the HV part of the PSU though.
Lastly, how can I make an oudin coil? I know that it is something similar to a tesla coil, but I can't find any clear guides on the internet. I can however borrow a USB plasma ball, would that be enough?

Click to expand...

There should be a resistor (or series of resistors) very near to one of the ends of the tube. Often it/they are "buried" in thermal potting in one of the endcaps.

I have no idea how to build an oudin coil.

I have no idea what a USB plasma ball is

Peace,
dave

daguin said:

There should be a resistor (or series of resistors) very near to one of the ends of the tube. Often it/they are "buried" in thermal potting in one of the endcaps.

I have no idea how to build an oudin coil.

I have no idea what a USB plasma ball is

Peace,
dave

Click to expand...

I don't think his HeNe has the ballast resistor in the head.

The USB plasma ball *should* be enough to excite the gas if you connect the plasma ball's HV output to the HV input on the HeNe tube and look for any light coming from the tube.

Hi,
If you need help ask Úvod - Tesla V.T. MIKROEL, s.r.o. - known as "TESLA - Vakuova technika" in past. They probably produced your laser... thirty years ago
Regards,
B.

"TESLA Vakuová technika, koncernový podnik, Praha
Výroba vakuových prvků — vysílacích elektronek, usměrňovačích elektronek (plněných plynem), vakuových thyratronů pro pulsní modulaci, reflexních a výkonových klystronů, magnetronů pro pulsní a trvalý provoz, karcino-tronů, kvantikonů, chalnikonů, křemikonů, vidikonů, fotonásobičů, kanálových násobičů elektronů, jednostopých obrazovek, trubic a výbojek pro lasery, vakuových kondenzátorů, He—Ne a C02 rubínových laserů. Výzkum a vývoj optoelektronických zařízení — snímacích prvků, rentgenových převaděčů, fotonásobičů, dále mikrovlnných a vysílacích elektronek, laserové techniky pro stavebnictví, doly a technologické účely a speciálních fyzikálních zařízení."

great, you have a source of high voltage in that plasma ball, what I would try first is wrapping some aluminum foil around the top or upper half of the plasma ball and attach a wire to it.
(you might even want to try doing the same to the inside portion of a regular CRT television set's screen)

Goal:
You are going to be trying to get a current flowing thru the tube and test to see if all its gas has leaked out and will not ionize any longer.

With the tube not connected to the power supply grab one of its power connector leads with your hand, now touch the other untouched lead to the plasma ball, do this
in the dark and look closely for both a spark from the lead to the ball and for ionization
inside of the tube. nothing? try the tv set, nothing? take apart the plasma ball and hit its output lead directly.


Goal:
You will be trying to provide the tube a start pulse THROUGH THE GLASS.

Power up that laser supply while hooked up to the laser.
very carefully try to hit the glass part only with the high voltage, ultimately you would want to do this towards the middle of the tube, far away from the ends. Be carefull to not hit the case or the leads, there may be a risk of damaging even the high voltage components.
You could also try triggering it with the trigger winding around the xenon flash tube in a disposable camera

try to get the tube ionizing, do you have a neon sigh transformer? hook it up across the tube, does it ionize? good, let it run for a while.. if you have a variac put that ahead of the NST and turn it up so you can go easy on the tube.. do you have a HV rectifier? put it in series and apply reverse voltage to the tube similarly

Take a disposable camera and swap out the xenon flash tube with your laser, apply the trigger pulse to the GLASS.

tips:

Do not touch that funky resistor, the oil on your fingers can hurt it.

You can try to remove the tube from the housing by running a hacksaw blade around it very carefully.

You can cook the tube only in an oven.

You can use RF induction to try to activate the getter within the tube to bury within it impurities.

You can put the tube within a rubber balloon and fill it with helium to try to force helium into the tube over time.

Hopefully the above gets some ideas flowing

p.s. it is interesting that the transistor says Tesla on it
that power supply looks very nice, good quality

goood luck.

Can't wait to see you get a beam going. Probably just needs the right power supply.

Many thanks LaserCo, I will try to do all the things on your list. I have talked to a guy that used to handle these back then, and I discovered that these "communist" tubes used to have a short lifetime, becuase they leaked helium. So I'll try to put the tube in a big helium balloon as LaserCo suggested.

Strap that PSU to your belt, and walk around using the head like a handheld. Yeah.

Joe Mo said:

Strap that PSU to your belt, and walk around using the head like a handheld. Yeah.

Click to expand...

Dont forget the 12V gel battery or 11.1v lipo and an inverter - isnt that a mains supply?