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Weird HeNe lab laser on ebay

MacDoktor

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This is my first thread here (I think) so go easy on me...

I'm baffled by this homemade lab laser on ebay:

Unknown/Like "HeNe Laser Kit -Box" From College Physics Lab Education Research

It looks like a tube with a brewster window which would require an external mirror but I can't figure out how it would have been held in place accurately enough to work.

There's also a BNC connector between the anode and the ballast resistor. Could that have been for an ammeter?

As for the big carbon comp resistors and HV capacitors I have no clue what's going on here. :unsure:
 



hakzaw1

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ACTUALLY your first thread/post should have been an 'intro' of yrself and placed in the welcome/newcomers section.
I will be watching for that--you very well could live close to a few members and getting together for show n tell is wonderful.... actually just being around folks who understand us is refreshing-- no 'whats up w/ you and those damn lazors ?-
Why do you need more than one-? and so on... LEMs are biggish gatherings where that happens.

IF you are not very familiar with SAM... you should be and HE IS THE MAN when it comes to old gas lasers.
If you are sure no info is there THEN you can send him an email about it=---pics help--links? we need those.
He even lists tubes by size==length and diameter.
I got to meet and hang w/ Sam at two SELEMs- (doing the 'not worthy' dance ATM)

IF you feel the need to NOT post your location (other than USA) you can trust me to intro you to members nearby.
I think you make already own a <LPM and are quite laser savvy.. IF you ever make a LEM be sure to bring your more exotic lasers.
At just one SELEM I have seen more lasers than I ever expected. So I came back 4 more times and hosted my own LEM and co-hosted a great TEXLEM in SanAntonio. AND met in person over 100 forum members.. their families and guests who attend the LEM just to watch free laser shows.


I own a dozen red HeNes- 6 argons(2 are MLs) BUT my prize came from Sam and while just 6 mW it is the most beautiful yellow 'light' I have ever seen. (btw it came w/o a PS and Sam gave me a discount so I paid only $300 for it.) I have two 534nm Reos I must sell a few so let me know if you are looking.
 

Anthony P

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Wow! What cobbled-up mess.
It hard to say from the pictures and there is no transformer/ power supply shown. The caps look to be paralleled likely for a filter. Small value hv caps are much much cheaper than high value. At first I suspected a multiplier circuit, but I don' see any diodes. It may be that aligning it using external mirrors was part of the student's task.
If you want a good HeNe, there are plenty available that won't break the bank.
Are you actually shopping for something particular or just curious about that mess?
 

paul1598419

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I would never pay $375 for a 632.8nm 1 mW HeNe. I have several all over that power level and none cost me near that much.

Edit: I just saw the listing for the $375 one has finished and the one you are talking about is under $20.00. But, it is not working either.
 

MacDoktor

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Are you actually shopping for something particular or just curious about that mess?
Just curious. It's so weird that I had to ask.

I would never pay $375 for a 632.8nm 1 mW HeNe. I have several all over that power level and none cost me near that much.
You're looking at the "We found something similar" auction. Click on the "View original item" link.

I have quite a few HeNe lasers and power supplies. I bought them some years back when the prices on ebay were a bit more reasonable. I have three green tubes and a yellow. I don't remember what I paid for the yellow tube but it was a bargain. My best 632.8nm is a 25" head from an as-is/can't test auction. $31 with shipping.

ACTUALLY your first thread/post should have been an 'intro' of yrself and placed in the welcome/newcomers section.
Yes, I just haven't had a chance to put some words together yet. I tend to ramble too much.

I will be watching for that--you very well could live close to a few members and getting together for show n tell is wonderful.... actually just being around folks who understand us is refreshing-- no 'whats up w/ you and those damn lazors ?-
Why do you need more than one-? and so on
I could bring along my Nixie gear and radioactive stuff.

I have two 534nm Reos I must sell a few so let me know if you are looking.
One of the reasons I've been lurking is that I don't know all the slang and acronyms yet. I have no clue what a "Reo" is but I'll catch on.

I'll reply to the rest of your post a little later. I need to work on my intro post. Thanks to everyone for replying.

Here's my (largely inactive) blog. I have quite a few things to post on it but haven't gotten around to yet. Try not to laugh too hard at my amateurish attempts at power measurements: A Star Close Up
 

Cyparagon

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"REO" is a company/manufacturer. Short for Research Electro-optics I believe.

My first thought was yes, the BNC may be for current sensing. I've reverse engineered it and I'll post a schematic in a few hours. This thing has 185k of ballast, which seems way high to me. After seeing the layout, I see no path for a high voltage pulse to start the tube, so my new guess is the BNC is for the starting pulse only.

Yes, I don't see any place for the mirrors, unless the mirrors themselves were mounted at brewster's angle? Perhaps the device was part of a larger fixture with the mirrors mounted on rails external to this box.
 

MacDoktor

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Yes, I don't see any place for the mirrors, unless the mirrors themselves were mounted at brewster's angle? Perhaps the device was part of a larger fixture with the mirrors mounted on rails external to this box.
I see a number of holes on the sides. Perhaps they were used to hold it in place.
 

Cyparagon

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The holes aren't threaded, nor are they symmetrical, so I think ventilation/expansion is more likely. Anyway, this is what I see in that circuit.

IMG_20190528_201551485.jpg


Looks like its past life included a diet of noisy DC and an external starter.
 

MacDoktor

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Now I see. The BNC is on the cathode. What kind of filter network is that? (obviously lowpass).
 

Cyparagon

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"RC filter" simply enough. As the name implies, this is comprised of resistance and capacitance.
 

MacDoktor

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I was just wondering if it was a more complex topology than a "simple" RC filter. It looks like three in series but I wanted to be sure.
 




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