Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from 1989 in a storage closet at my school that I'm trying to get to energize. My degree is in electrical engineering, so I'm not unfamiliar with troubleshooting electronics, but I've never worked with laser electronics, especially not from the 80s. The device requires a key to activate a switch, which I cannot find, but I was able to use a paperclip, while the device was unplugged, to attempt to rotate the lock mechanism into the "on" position. Now, I'm not sure if this rotated the actual switch or just some part of the lock, so the source of this entire problem could be that I am missing that key.. If this is so, how could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a paperclip" method should have turned it on, does anyone know of any common failures with this model laser? The power light on the back does not even turn on, so if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks

You should be able to get a key made by a locksmith. Baring that, key
switches are easy to find with new keys. You could remove the key switch and
install a common toggle switch for trouble shooting the laser tube.

Most likely you will find the tube will not start. Over the years, the He
gas has migrated through the glass and the seals and will be at low
pressure.

If this is the case, It is possible to soak the tube in a He atmosphere and
He will diffuse back into the tube. This will take a few days to do and you
will need to check it frequently

tm


wrote in message
...
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from
1989 in a storage closet at my school that I'm trying to get to energize. My
degree is in electrical engineering, so I'm not unfamiliar with
troubleshooting electronics, but I've never worked with laser electronics,
especially not from the 80s. The device requires a key to activate a switch,
which I cannot find, but I was able to use a paperclip, while the device was
unplugged, to attempt to rotate the lock mechanism into the "on" position.
Now, I'm not sure if this rotated the actual switch or just some part of the
lock, so the source of this entire problem could be that I am missing that
key. If this is so, how could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a paperclip"
method should have turned it on, does anyone know of any common failures
with this model laser? The power light on the back does not even turn on, so
if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks

On 9/10/2013 8:53 AM, tm wrote:
You should be able to get a key made by a locksmith. Baring that, key
switches are easy to find with new keys. You could remove the key switch
and install a common toggle switch for trouble shooting the laser tube.

Most likely you will find the tube will not start. Over the years, the
He gas has migrated through the glass and the seals and will be at low
pressure.

If this is the case, It is possible to soak the tube in a He atmosphere
and He will diffuse back into the tube. This will take a few days to do
and you will need to check it frequently

tm


wrote in message
...
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser
from 1989 in a storage closet at my school that I'm trying to get to
energize. My degree is in electrical engineering, so I'm not unfamiliar
with troubleshooting electronics, but I've never worked with laser
electronics, especially not from the 80s. The device requires a key to
activate a switch, which I cannot find, but I was able to use a
paperclip, while the device was unplugged, to attempt to rotate the lock
mechanism into the "on" position. Now, I'm not sure if this rotated the
actual switch or just some part of the lock, so the source of this
entire problem could be that I am missing that key. If this is so, how
could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a
paperclip" method should have turned it on, does anyone know of any
common failures with this model laser? The power light on the back does
not even turn on, so if it is a failure, I imagine it's with the power
supply.

Any and all suggestions would be appreciated.

Thanks
IF there is a number on the metal part of the switch, a locksmith can
make you a key based on that number.

Paul

wrote:
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from 1989 in a storage closet at my school that I'm trying to get to energize. My degree is in electrical engineering, so I'm not unfamiliar with troubleshooting electronics, but I've never worked with laser electronics, especially not from the 80s. The device requires a key to activate a switch, which I cannot find, but I was able to use a paperclip, while the device was unplugged, to attempt to rotate the lock mechanism into the "on" position. Now, I'm not sure if this rotated the actual switch or just some part of the lock, so the source of this entire problem could be that I am missing that key. If this is so, how could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a paperclip" method should have turned it on, does anyone know of any common failures with this model laser? The power light on the back does not even turn on, so if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks

bypass the switch.

there's no reason to have a keyswitch on some old dead laser.

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.

"Cydrome Leader" wrote in message
...
wrote:
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser
from 1989 in a storage closet at my school that I'm trying to get to
energize. My degree is in electrical engineering, so I'm not unfamiliar
with troubleshooting electronics, but I've never worked with laser
electronics, especially not from the 80s. The device requires a key to
activate a switch, which I cannot find, but I was able to use a
paperclip, while the device was unplugged, to attempt to rotate the lock
mechanism into the "on" position. Now, I'm not sure if this rotated the
actual switch or just some part of the lock, so the source of this entire
problem could be that I am missing that key. If this is so, how could I
obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a
paperclip" method should have turned it on, does anyone know of any
common failures with this model laser? The power light on the back does
not even turn on, so if it is a failure, I imagine it's with the power
supply.

Any and all suggestions would be appreciated.

Thanks

bypass the switch.

there's no reason to have a keyswitch on some old dead laser.

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.

Wow, you need to find a better locksmith. I needed a key for a portable
pulsed x-ray source and took it to a good locksmith. He looked up the lock
number and sold me two keys for $6 something.

I agree with you that the laser will most likely be dead but might be
recoverable with a He soak.

I am pretty sure that a key switch is required by the FDA depending on the
laser power. Considering he is a HS teacher and may be using this around
students, the key switch is a good thing to have.


This space reserved for snarkey comments.
-----------------------------------------------------------------

On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:
"Cydrome Leader" wrote in message

...

wrote:

Hi Folks,



I'm a high school physics teacher, and just found an ML855 HeNe Laser

from 1989 in a storage closet at my school that I'm trying to get to

energize. My degree is in electrical engineering, so I'm not unfamiliar

with troubleshooting electronics, but I've never worked with laser

electronics, especially not from the 80s. The device requires a key to

activate a switch, which I cannot find, but I was able to use a

paperclip, while the device was unplugged, to attempt to rotate the lock

mechanism into the "on" position. Now, I'm not sure if this rotated the

actual switch or just some part of the lock, so the source of this entire

problem could be that I am missing that key. If this is so, how could I

obtain a replacement key for this unit?



If this is not the case, and you think my "jimmy the lock with a

paperclip" method should have turned it on, does anyone know of any

common failures with this model laser? The power light on the back does

not even turn on, so if it is a failure, I imagine it's with the power

supply.



Any and all suggestions would be appreciated.



Thanks



bypass the switch.



there's no reason to have a keyswitch on some old dead laser.



You'll also find a new keyswitch from digikey or newark will cost less

than talking to a locksmith.



Wow, you need to find a better locksmith. I needed a key for a portable

pulsed x-ray source and took it to a good locksmith. He looked up the lock

number and sold me two keys for $6 something.



I agree with you that the laser will most likely be dead but might be

recoverable with a He soak.



I am pretty sure that a key switch is required by the FDA depending on the

laser power. Considering he is a HS teacher and may be using this around

students, the key switch is a good thing to have.





This space reserved for snarkey comments.

-----------------------------------------------------------------

Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Thanks again.

On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:
On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:

snip previous stuff


Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

George H




Thanks again.

writes:

On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:
On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:

snip previous stuff


Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

If it is less than about 30 years old, the tube is hard-sealed and
doesn't really leak. An ML855 could be function like new.

Bypasss or replace the switch and see what happens.

Just be careful of the line voltage and high voltage inside!

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

On 09/10/2013 1:06 PM, wrote:
On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:
On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:

snip previous stuff


Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

George H




Thanks again.


HeNe is cool retro-tech, laser diodes are cheating...

I have three HeNe tubes that need a new home - can test them to make
sure still alive, they were for a Panasonic Laser Disc player from the
early 80s...and did work the last time I tested them in 2006.

John :-#)#

--
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

"Cydrome Leader" wrote in message ...

wrote:
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from
1989 in a storage closet at my school that I'm trying to get to energize.
My degree is in electrical engineering, so I'm not unfamiliar with
troubleshooting electronics, but I've never worked with laser electronics,
especially not from the 80s. The device requires a key to activate a
switch, which I cannot find, but I was able to use a paperclip, while the
device was unplugged, to attempt to rotate the lock mechanism into the
"on" position. Now, I'm not sure if this rotated the actual switch or just
some part of the lock, so the source of this entire problem could be that
I am missing that key. If this is so, how could I obtain a replacement key
for this unit?

If this is not the case, and you think my "jimmy the lock with a
paperclip" method should have turned it on, does anyone know of any common
failures with this model laser? The power light on the back does not even
turn on, so if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks

bypass the switch.

there's no reason to have a keyswitch on some old dead laser.

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though. The little laser pointer that you can buy all over
that work off of watch batterys are in the same range of power. A HeNe tube
puts out a much better quality of laser light and more coherent than a
little laser pointer and it will be most likely red light. You won't see
the beam at these low power levels, just a intense bright spot on what ever
you aim it at. Note that the brightness of the spot is much brighter that
our eyes can determine. If it is low power like I'm guessing, I don't think
you need the key switch; just replace it with a toggle switch, I think US
and Canada changed the rules on low power laser otherwise you wouldn't be
able to by a laser pointer toy.

The power supply to power the HeNe tube run around 2000 volts and some put
out a pulse to start the tube up to a voltage of around 10,000 volts. They
draw a few milliamps. So watch out not to shock yourself if you touch
anything inside the chassis. Also note that after the power is turned off,
the laser tube holds a charge on it and if you touch the wrong area you'll
get an unpleasant shock - guess how I know this :-)

Good luck!

Shaun

Roger kom med denne ide:

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though.

Sign: Don't look into laser with remaining good eye.

--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

In article ,
Roger wrote:

I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though. The little laser pointer that you can buy all over
that work off of watch batterys are in the same range of power. A HeNe tube
puts out a much better quality of laser light and more coherent than a
little laser pointer and it will be most likely red light. You won't see
the beam at these low power levels, just a intense bright spot on what ever
you aim it at. Note that the brightness of the spot is much brighter that
our eyes can determine. If it is low power like I'm guessing, I don't think
you need the key switch; just replace it with a toggle switch, I think US
and Canada changed the rules on low power laser otherwise you wouldn't be
able to by a laser pointer toy.

The ML855 seems to be rated as a 5 mW laser.

According to the Great Font of Trackless Factoids (i.e. Wikipedia)
this is right at the upper limit of Class 3R ("considered safe if
handled carefully, with restricted beam viewing"). It's well above
the 1 mW limit for Class 2 lasers ("safe because the blink reflex will
limit the exposure to more than 0.25 seconds") which is usually the
category in which you find inexpensive laser pointers, I believe.

Anything above 5 mW is at least Class 3B, which does require a key
switch and a safety interlock.

So, replacing the keyswitch with a new one, rather than with a toggle,
would be prudent. Otherwise, the laser might someday end up being
toggled on by someone who thought it was no brighter (or more
hazardous) than a $2 laser pointer, and careless use might result in
someone's eye being damaged.

On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:

On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:



snip previous stuff


Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.
http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

George H.

If it is less than about 30 years old, the tube is hard-sealed and
doesn't really leak. An ML855 could be function like new

Bypasss or replace the switch and see what happens.

Just be careful of the line voltage and high voltage inside!



--

sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/

Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/

+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm

| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html



Important: Anything sent to the email address in the message header above is

ignored unless my full name AND either lasers or electronics is included in the

subject line. Or, you can contact me via the Feedback Form in the FAQs.

On Tuesday, September 10, 2013 5:36:41 PM UTC-4, Roger wrote:
"Cydrome Leader" wrote in message ...



wrote:

Hi Folks,



I'm a high school physics teacher, and just found an ML855 HeNe Laser from

1989 in a storage closet at my school that I'm trying to get to energize.

My degree is in electrical engineering, so I'm not unfamiliar with

troubleshooting electronics, but I've never worked with laser electronics,

especially not from the 80s. The device requires a key to activate a

switch, which I cannot find, but I was able to use a paperclip, while the

device was unplugged, to attempt to rotate the lock mechanism into the

"on" position. Now, I'm not sure if this rotated the actual switch or just

some part of the lock, so the source of this entire problem could be that

I am missing that key. If this is so, how could I obtain a replacement key

for this unit?



If this is not the case, and you think my "jimmy the lock with a

paperclip" method should have turned it on, does anyone know of any common

failures with this model laser? The power light on the back does not even

turn on, so if it is a failure, I imagine it's with the power supply.



Any and all suggestions would be appreciated.



Thanks



bypass the switch.



there's no reason to have a keyswitch on some old dead laser.



You'll also find a new keyswitch from digikey or newark will cost less

than talking to a locksmith.

-----------------------------------------------------------------------------------------------------------------------------

I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5

feet in length; they are usually 1 milli-watt to 5 milli-watts laser output

power. You would not want to get the beam directly in your eye, it could

cause some damage. I have heard that the eye very quickly turns to avoid

being damaged though. The little laser pointer that you can buy all over

that work off of watch batterys are in the same range of power. A HeNe tube

puts out a much better quality of laser light and more coherent than a

little laser pointer and it will be most likely red light. You won't see

the beam at these low power levels, just a intense bright spot on what ever

you aim it at. Note that the brightness of the spot is much brighter that

our eyes can determine. If it is low power like I'm guessing, I don't think

you need the key switch; just replace it with a toggle switch, I think US
and Canada changed the rules on low power laser otherwise you wouldn't be
able to by a laser pointer toy.



The power supply to power the HeNe tube run around 2000 volts and some put
out a pulse to start the tube up to a voltage of around 10,000 volts. They
draw a few milliamps. So watch out not to shock yourself if you touch
anything inside the chassis. Also note that after the power is turned off,
the laser tube holds a charge on it and if you touch the wrong area you'll
get an unpleasant shock - guess how I know this :-)



Good luck!



Shaun
Hi Shaun, Certainly the beam profile is better in a HeNe.

I'm not sure what you mean by 'more coherent', but for the few diode lasers I've looked at - compared to the short cavity HeNe that I have, the diode lasers had a longer coherence length.
(Which struck me as a bit weird the first time I saw it... I had this mistaken belief that the coherence length was related to the cavity length.)
I'm not sure if the long cavity HeNe's have a longer or shorter coherence length when compared to the short cavities... Perhaps Sam will educate us.

George H.

On 09/10/2013 07:15 AM, wrote:
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from 1989 in a storage closet at my school that I'm trying to get to energize. My degree is in electrical engineering, so I'm not unfamiliar with troubleshooting electronics, but I've never worked with laser electronics, especially not from the 80s. The device requires a key to activate a switch, which I cannot find, but I was able to use a paperclip, while the device was unplugged, to attempt to rotate the lock mechanism into the "on" position. Now, I'm not sure if this rotated the actual switch or just some part of the lock, so the source of this entire problem could be that I am missing that key. If this is so, how could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a paperclip" method should have turned it on, does anyone know of any common failures with this model laser? The power light on the back does not even turn on, so if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks


They go soft if you don't use them. The gases get unmixed. You may get
it to come back but probably not.

09/10/2013On Tue, 10 Sep 2013 23:41:52 +0200, Leif Neland
wrote:

Roger kom med denne ide:

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though.

Sign: Don't look into laser with remaining good eye.


I worked for a company in the mid 80s that sold Pioneer Laser Disc
players. A high school kid came in one day who experimented with the
laser tubes from these players. He had holes burnt into the iris of
one of his eyes. Chuck

writes:

On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:

On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:



snip previous stuff


Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.
http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though
perhaps that is a bit of a stretch for an intro to lasers in high school.

But one can do some nice interferometry experiments with not much additional
equipment.

In fact, I see you your Web site that you do some of these things.

A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

The beam quality is also a lot better than most diode lasers (divergence,
beam profile).

With some you can put another mirror in front or in back of the laser
(if accessible) and get 1 or more of the other HeNe wavelengths.

I can go on and on.....

Contact me directly via repairfaq.org if you'd like.
--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.




George H.

If it is less than about 30 years old, the tube is hard-sealed and
doesn't really leak. An ML855 could be function like new

Bypasss or replace the switch and see what happens.

Just be careful of the line voltage and high voltage inside!

writes:

On Tuesday, September 10, 2013 5:36:41 PM UTC-4, Roger wrote:
"Cydrome Leader" wrote in message ...



wrote:

Hi Folks,



I'm a high school physics teacher, and just found an ML855 HeNe Laser from

1989 in a storage closet at my school that I'm trying to get to energize.

My degree is in electrical engineering, so I'm not unfamiliar with

troubleshooting electronics, but I've never worked with laser electronics,

especially not from the 80s. The device requires a key to activate a

switch, which I cannot find, but I was able to use a paperclip, while the

device was unplugged, to attempt to rotate the lock mechanism into the

"on" position. Now, I'm not sure if this rotated the actual switch or just

some part of the lock, so the source of this entire problem could be that

I am missing that key. If this is so, how could I obtain a replacement key

for this unit?



If this is not the case, and you think my "jimmy the lock with a

paperclip" method should have turned it on, does anyone know of any common

failures with this model laser? The power light on the back does not even

turn on, so if it is a failure, I imagine it's with the power supply.



Any and all suggestions would be appreciated.



Thanks



bypass the switch.



there's no reason to have a keyswitch on some old dead laser.



You'll also find a new keyswitch from digikey or newark will cost less

than talking to a locksmith.

-----------------------------------------------------------------------------------------------------------------------------

I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5

feet in length; they are usually 1 milli-watt to 5 milli-watts laser output

power. You would not want to get the beam directly in your eye, it could

cause some damage. I have heard that the eye very quickly turns to avoid

being damaged though. The little laser pointer that you can buy all over

that work off of watch batterys are in the same range of power. A HeNe tube

puts out a much better quality of laser light and more coherent than a

little laser pointer and it will be most likely red light. You won't see

the beam at these low power levels, just a intense bright spot on what ever

you aim it at. Note that the brightness of the spot is much brighter that

our eyes can determine. If it is low power like I'm guessing, I don't think

you need the key switch; just replace it with a toggle switch, I think US
and Canada changed the rules on low power laser otherwise you wouldn't be
able to by a laser pointer toy.



The power supply to power the HeNe tube run around 2000 volts and some put
out a pulse to start the tube up to a voltage of around 10,000 volts. They
draw a few milliamps. So watch out not to shock yourself if you touch
anything inside the chassis. Also note that after the power is turned off,
the laser tube holds a charge on it and if you touch the wrong area you'll
get an unpleasant shock - guess how I know this :-)



Good luck!



Shaun
Hi Shaun, Certainly the beam profile is better in a HeNe.

I'm not sure what you mean by 'more coherent', but for the few diode lasers I've looked at - compared to the short cavity HeNe that I have, the diode lasers had a longer coherence length.
(Which struck me as a bit weird the first time I saw it... I had this mistaken belief that the coherence length was related to the cavity length.)
I'm not sure if the long cavity HeNe's have a longer or shorter coherence length when compared to the short cavities... Perhaps Sam will educate us.

George H.

It's a crap shoot. Some diodes have exception coherence length but
many/most are very short.

--
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dave writes:

On 09/10/2013 07:15 AM, wrote:
Hi Folks,

I'm a high school physics teacher, and just found an ML855 HeNe Laser from 1989 in a storage closet at my school that I'm trying to get to energize. My degree is in electrical engineering, so I'm not unfamiliar with troubleshooting electronics, but I've never worked with laser electronics, especially not from the 80s. The device requires a key to activate a switch, which I cannot find, but I was able to use a paperclip, while the device was unplugged, to attempt to rotate the lock mechanism into the "on" position. Now, I'm not sure if this rotated the actual switch or just some part of the lock, so the source of this entire problem could be that I am missing that key. If this is so, how could I obtain a replacement key for this unit?

If this is not the case, and you think my "jimmy the lock with a paperclip" method should have turned it on, does anyone know of any common failures with this model laser? The power light on the back does not even turn on, so if it is a failure, I imagine it's with the power supply.

Any and all suggestions would be appreciated.

Thanks


They go soft if you don't use them. The gases get unmixed. You may get
it to come back but probably not.

IF they are soft-seal. If newer than around 30 years of age, they will be
hard-seal with an essentially infinite shelf life.

Running a soft seal tube that has a decently bright discharge may get it
to come back to life after anywhere from a few hours to months.

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"chuck" wrote in message ...

09/10/2013On Tue, 10 Sep 2013 23:41:52 +0200, Leif Neland
wrote:

Roger kom med denne ide:

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser
output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though.

Sign: Don't look into laser with remaining good eye.


I worked for a company in the mid 80s that sold Pioneer Laser Disc
players. A high school kid came in one day who experimented with the
laser tubes from these players. He had holes burnt into the iris of
one of his eyes. Chuck
------------------------------------------------------------------------------------------------
Bull****!

A read laser does not have that much power. If it was a CD Burner - then
that could happen. With a regular CD player, the laser might damage the
Retina which is at the back inside of the eye ball, it converts what we see
into a signal that our brain decodes as an image.

I would still like to know why it is allowed that anyone can buy a handheld
diode laser under 5 milliwatts without any safeties or adult supervision.
They can do lots of damage!

Roger

On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:
writes:
On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:

writes:







On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:



On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:
snip previous stuff
Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.



Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.
Actually quite a lot.
Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.

http://teachspin.com/instruments/moderni/index.shtml
The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.



But one can do some nice interferometry experiments with not much additional

equipment.
In fact, I see you your Web site that you do some of these things.
A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

Hi Sam, Thanks for the response. You're talking about sending the laser into a F-P and looking at the output? A flat mirror F-P (Etalon), a confocal curved mirror F-P, or something in between?



The beam quality is also a lot better than most diode lasers (divergence,

beam profile).



With some you can put another mirror in front or in back of the laser

(if accessible) and get 1 or more of the other HeNe wavelengths.
Yeah there are lots of fun things if you allow for access to the cavity. I recall fondly an argon laser in grad school, that was equipped with a grating and mirror on one side... you could tune through all the Argon lines. There is a certain beauty in the 'pure' blue colors.
I can go on and on.....
Contact me directly via repairfaq.org if you'd like.

Thanks Again,

George H.

--

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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/

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George H.



If it is less than about 30 years old, the tube is hard-sealed and

doesn't really leak. An ML855 could be function like new



Bypasss or replace the switch and see what happens.



Just be careful of the line voltage and high voltage inside!

On Wed, 11 Sep 2013 21:32:45 -0500, "Shaun"
wrote:



"chuck" wrote in message ...

09/10/2013On Tue, 10 Sep 2013 23:41:52 +0200, Leif Neland
wrote:

Roger kom med denne ide:

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser
output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though.

Sign: Don't look into laser with remaining good eye.


I worked for a company in the mid 80s that sold Pioneer Laser Disc
players. A high school kid came in one day who experimented with the
laser tubes from these players. He had holes burnt into the iris of
one of his eyes. Chuck
------------------------------------------------------------------------------------------------
Bull****!

A read laser does not have that much power. If it was a CD Burner - then
that could happen. With a regular CD player, the laser might damage the
Retina which is at the back inside of the eye ball, it converts what we see
into a signal that our brain decodes as an image.

I would still like to know why it is allowed that anyone can buy a handheld
diode laser under 5 milliwatts without any safeties or adult supervision.
They can do lots of damage!

Roger


The kid did have holes in his iris, maybe he experimented with other
more powerful lasers that I didn't know about. Chuck

On Wednesday, September 11, 2013 3:58:24 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Tuesday, September 10, 2013 5:36:41 PM UTC-4, Roger wrote:

"Cydrome Leader" wrote in message ...

snip

Shaun

Hi Shaun, Certainly the beam profile is better in a HeNe.



I'm not sure what you mean by 'more coherent', but for the few diode lasers I've looked at - compared to the short cavity HeNe that I have, the diode lasers had a longer coherence length.

(Which struck me as a bit weird the first time I saw it... I had this mistaken belief that the coherence length was related to the cavity length.)

I'm not sure if the long cavity HeNe's have a longer or shorter coherence length when compared to the short cavities... Perhaps Sam will educate us.



George H.
It's a crap shoot. Some diodes have exception coherence length but
many/most are very short.

OK that's good to know. It'd be nice if someone had a list of good diode lasers. The one we use is from US lasers M650-5I. ~$33 from digikey. We have a couple of others but I never looked at the coherence length.

George H.



--

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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/

+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm

| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html



Important: Anything sent to the email address in the message header above is

ignored unless my full name AND either lasers or electronics is included in the

subject line. Or, you can contact me via the Feedback Form in the FAQs.

writes:

On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:
writes:
On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:

writes:







On Tuesday, September 10, 2013 3:02:50 PM UTC-4, wrote:



On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:
snip previous stuff
Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.



Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.
Actually quite a lot.
Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.

http://teachspin.com/instruments/moderni/index.shtml
The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though
perhaps that is a bit of a stretch for an intro to lasers in high school.
But one can do some nice interferometry experiments with not much
additional equipment.

In fact, I see you your Web site that you do some of these things.
A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)
Hi Sam, Thanks for the response. You're talking about sending the
laser into a F-P and looking at the output? A flat mirror F-P
(Etalon), a confocal curved mirror F-P, or something in between?

Generally, a confocal FP is best since it greatly simplifies alignment.

For the HeNe, the mirror Radius of Curvature (RoC) of both mirrors needs
to be less than about 50 mm so that the Free Spectral Range (FSR, or
mode spacing of the FP) is larger than the gain bandwidth of the
HeNe red transition.

One of the FP mirrors is then mounted on a piezo transducer (PZT) and
the FP is scanned rather than the laser. The PZT can be the beeper
element from a digital gizmo or less than $2 from Digikey.

More info at: http://www.repairfaq.org/sam/laserlia.htm#liasfpi

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
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On Thursday, September 12, 2013 4:10:39 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:

snip stuff to get rid of double spaces

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.



http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.



What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.

But one can do some nice interferometry experiments with not much

additional equipment.



In fact, I see you your Web site that you do some of these things.

A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

Hi Sam, Thanks for the response. You're talking about sending the

laser into a F-P and looking at the output? A flat mirror F-P

(Etalon), a confocal curved mirror F-P, or something in between?



Generally, a confocal FP is best since it greatly simplifies alignment.



For the HeNe, the mirror Radius of Curvature (RoC) of both mirrors needs

to be less than about 50 mm so that the Free Spectral Range (FSR, or

mode spacing of the FP) is larger than the gain bandwidth of the

HeNe red transition.

One of the FP mirrors is then mounted on a piezo transducer (PZT) and

the FP is scanned rather than the laser. The PZT can be the beeper

element from a digital gizmo or less than $2 from Digikey.

More info at: http://www.repairfaq.org/sam/laserlia.htm#liasfpi

OK you may like this, I have only a few youtube videos.
http://www.youtube.com/watch?v=geQVSrXN3tE
I'm sending a diode laser into a confocal cavity, (20 cm mirrors)
with the cavity length set maybe 1cm short, so all the modes, don't all fall at the same wavlength. I'm then scanning the laser wavlength, and have a bare CCD camera (no lens) pointing into the back end of the cavity. This video has mostly just the even modes* but the others show both odd and even..

George H.
*if you get the laser 'smack dab' down the middle you lose 'most' of the odd modes.

--

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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/

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Important: Anything sent to the email address in the message header above is

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writes:

On Thursday, September 12, 2013 4:10:39 PM UTC-4, Samuel M. Goldwasser wrote:
writes:



On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:

snip stuff to get rid of double spaces

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.



http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.



What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.

But one can do some nice interferometry experiments with not much

additional equipment.



In fact, I see you your Web site that you do some of these things.

A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

Hi Sam, Thanks for the response. You're talking about sending the

laser into a F-P and looking at the output? A flat mirror F-P

(Etalon), a confocal curved mirror F-P, or something in between?



Generally, a confocal FP is best since it greatly simplifies alignment.



For the HeNe, the mirror Radius of Curvature (RoC) of both mirrors needs

to be less than about 50 mm so that the Free Spectral Range (FSR, or

mode spacing of the FP) is larger than the gain bandwidth of the

HeNe red transition.

One of the FP mirrors is then mounted on a piezo transducer (PZT) and

the FP is scanned rather than the laser. The PZT can be the beeper

element from a digital gizmo or less than $2 from Digikey.

More info at: http://www.repairfaq.org/sam/laserlia.htm#liasfpi

OK you may like this, I have only a few youtube videos.
http://www.youtube.com/watch?v=geQVSrXN3tE
I'm sending a diode laser into a confocal cavity, (20 cm mirrors)
with the cavity length set maybe 1cm short, so all the modes, don't all fall at the same wavlength. I'm then scanning the laser wavlength, and have a bare CCD camera (no lens) pointing into the back end of the cavity. This video has mostly just the even modes* but the others show both odd and even.


George H.
*if you get the laser 'smack dab' down the middle you lose 'most' of the odd modes.

I assume you are seeing a combination of the laser modes (if not single
longitudinal mode) and the off-axis cavity modes. It may be possible to
determine the spectrum of the diode laser from the video but that's above
my pay grade.

--
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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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