Power variation on HeNe tube?

[Philip Pemberton]

Hi guys,

I've picked up an old NEC GLG2056 helium-neon laser (manufacture date
1981-10), and it's exhibiting some odd (to me) effects. Of course given
that my experience with lasers is mostly with the semiconductor type,
it's highly likely I'm just being an idiot ;)

When I powered the laser up, the output power fluctuated between ~1008
and ~1070 microwatts over the course of a few minutes. In fact, it's
still doing this...

Is this something I should be worried about, i.e. indicative of a failing
component?

When I opened the cover, I also noticed a pinprick sized laser spot
exiting the tube from the rear reflector. The laser seems to be running
normally otherwise...

The parts look fairly simple - a fuse holder, a key switch (jammed in the
ON position), a transformer, a small PCB, a few capacitors and other
parts on said PCB and the laser tube itself. Certainly nothing impossible
to repair if need be, though the tube might be a bit of a dog to replace.

Thanks,

[Samuel M. Goldwasser]

Both normal.

http://repairfaq.cis.upenn.edu/Misc/laserhen.htm#henmdsw

The small beam from the back is called the waste beam, due to a high reflector
that isn't perfect.
--
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Post by Philip Pemberton
Hi guys,
I've picked up an old NEC GLG2056 helium-neon laser (manufacture date
1981-10), and it's exhibiting some odd (to me) effects. Of course given
that my experience with lasers is mostly with the semiconductor type,
it's highly likely I'm just being an idiot ;)
When I powered the laser up, the output power fluctuated between ~1008
and ~1070 microwatts over the course of a few minutes. In fact, it's
still doing this...
Is this something I should be worried about, i.e. indicative of a failing
component?
When I opened the cover, I also noticed a pinprick sized laser spot
exiting the tube from the rear reflector. The laser seems to be running
normally otherwise...
The parts look fairly simple - a fuse holder, a key switch (jammed in the
ON position), a transformer, a small PCB, a few capacitors and other
parts on said PCB and the laser tube itself. Certainly nothing impossible
to repair if need be, though the tube might be a bit of a dog to replace.
Thanks,
--
Phil.
http://www.philpem.me.uk/