Forum der Vereinigung der Sternfreunde

Tonight I was going to focus my camera on my recently acquired Lhires III!..
For that operation I was counting on the internal Neon lamp! However, I discovered that my Neon is a very special kind of Neon that has a huge absorption region all the way from UV to IR!! In fact, if I did not know better, I would guess its spectrum matches quite well that of a Burnt-Neon lamp, or an Unlit-Neon lamp placed in front of the slit! (I don't know the chemical element name for these special variations of Neon... Probably "BNe" or "UNe" lamps - Yeah, I need to laugh a bit to avoid getting depressed or developing strange emotions towards the previous owner of the spectroscope)

I have to admit I have never seen a Ne lamp before, but being a gas-discharge lamp, I should see no broken filament inside, right? So there is no such thing as a Burnt Neon lamp !? How do I identify it as a bad (Unlit Neon) bulb? Perhaps some dark coloring of the glass on the inside?...

What would be the most plausible cause for a Ne lamp that is not working? Is it likely to be the inverter circuitry instead of the lamp (like it commonly happens in laptop LCD screens) ?
How should I debug my lamp to find out? the green LED on the switch lights green, but the Neon stays black.. I'm using 12V DC power, I should not have the + and - wrong because the green LED goes ON.

Thank you!

_________________
Fil.

Hi Fil

I think your lamp is broken. Ask Shelyak to get a new one.

Could you show some pics of the "neon-spectra" and the lamp?

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

Hi Fil,

Neon lamps are usually very reliable so I think it is more likely that the inverter is faulty or perhaps the flexible wire to the neon is broken. You could try checking the voltage at the neon but the current output of the inverter will be very low and the frequency is high so some meters do not measure this well. Alternatively you could disconnect the neon lamp and test it on the mains with a 100k resistor in series (Take care!)

You can see how to dismantle the LHIRES to get to the inverter here
http://www.astrosurf.com/thizy/lhires3/index-en.html

Robin

The voltage is ~100V AC and the circuit is here
http://www.astrosurf.com/thizy/lhires3/plan_neon_ci.pdf
http://www.astrosurf.com/thizy/lhires3/DSCN6753.JPG

Robin

Fil,

Another thing to check is that you are supplying at least 12v (The green LED will still light at a lower voltage but the voltage output will be too low to strike the neon.)

Robin

I replied earlier, but the Forum software did create a new thread instead
of attaching it to this thread:

Verfasst am: 2011-03-27, 11:26:02 Titel: Possible causes for dead Neons!

Hi Filipe

Did you already check if the voltage of the power supply to the Lhires III's internal
Neon lamp is high enough ?

How long did you operate the Lhires III's internal Neon lamp before taking images ?

Some gas discharpe lamps first show a continuum with absorbition when they are
cold and later on turn to an emission spectrum when they are hot enough.

Clear skies
Wolfgang

--
Wolfgang Renz, Karlsruhe, Germany

Daniel, sorry to have mislead you, my "absorption spectrum" was a joke.. I was referring to the shadow of an opaque lamp holder and unlit lamp
The lamp does not light up at all.. I really had to make a joke out of this, because I felt stupid after spending about 15~20 minutes doing long exposures and turning the micrometer searching for unfocused neon lines, on a bulb that was not working!


My electrical skills are so bad, I need to do anything very carefully and slowly, to make sure I am not doing anything wrong..

I will disassemble the side plate of the Lhires to look at the lamp and wires..

I will also be looking at the input voltages.. It should be ok, because I am using a regulated power supply (switching)..
Could there be some interference between the power supply and the inverter circuit ? I also will try with a non-switching power supply..

Wolfgang, the Neon must have been ON for about 1 minutes before I started imaging for emission lines, but then I left it ON for 15 minutes or so.. I suspect the lamp was not lit during the whole time, because I turned the micrometer from red to blue and I saw no line, not even a trace..

Thank you all for these clues..

_________________
Fil.

Hi Fil
I have used a switched mode power supply without any problem so it should be ok. I have occasionally had a problem with the connector (some slight corrosion perhaps) but unplugging and plugging it in again solved it. It does not sound like this is your problem though if the switch LED is lighting up.

Robin

Hi Fil,

Do you have a chance of talking Josè Ribeiro face-to-face. I remember
his great achievements of repairing LiHresIII with non-working neon.

Your problem seems to be caused by a broken wire or a cold solder joint
(which sometimes occurs in electronic systems short after delivery .

Regards,
Thomas

PS. The message opened a new thread. Never do I answer via an e-mail in the future...

Hi Thomas,

My main problem now is not so much in solving issues, it is in having spare time for doing it..
I don't like to pass on my problems to others when I am unable to be part of them, or at least observe well what is being done. But I hope to at least identify the problem during this week. I have taken the Neon "stuff" out of the Lhiers already.. So now is only a matter of doing things carefully.

_________________
Fil.

Hello Fil,

it would be better, if you use a opaque paper as diffusor accross the neon lamp. It is recommended by Shelyak and C. Buil.

See Foto of mine Lhires.

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Thank you Lothar,

Yes that is a good idea. I wanted to do that as well, specially after reading all your concerns for reproducibility of flats...
I noticed you placed the paper on the out side, I was thinking of placing it inside the tube, actually in contact with the bulb.. Do you foresee any problem in doing it this way?

_________________
Fil.

Hello Fil,

that is all the same. The cooling of the bulb is better, if the paper is outside. But the power of the bulb is low. Temperature increasing will be tolerable, I think.

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Hello Fil,

The diffusing paper was part of the original kit so should have been fitted. You can see it in this image here for example.
http://www.astrosurf.com/thizy/lhires3/IMG_9019.JPG

Robin