Hi Patrick,
Have you got any idea how long the device
has been inactive ?
Does the PSU contain any electrolyte caps
in the "lower voltage" stages?
They may depolarise if not used frequently
Such caps have to be repolarized very gently!
(see previous threads)
If the PSU contains a HV-Cap-Diode cascade
you could check the diodes. Checking the HV-caps
will be more of a problem without some decent
equipment.
Does it have some kind of overload or safety
protection circuit that kicks in to soon ?
Could the the HE-NE-tube have a micro crack?
I once had one with such a crack and it operated
only for half a minute. Then I heard some strang sissing
sound and the show was over. The small increase
in temp due to the device operating was enough
to open the crack just a tiny little bit more and the
"vacume" was gone... Finito.
Upon carefull inspection I later found the crack.
If you hopefully get it working again but don't be surprised
if the power is somewhat less than expected. The "mirrors"
at both ends of the tube will have been "worn out" if
the laser has been operated intensively. I've had
(another) HE-laser with that problem. You could
still do funny things with it in the dark but it produced
less than a tenth the light of a .5mW Diode Laser
It later turned out to have been used continuesly as
part of a fog-visibilitly measuringdevice for over more
than 5 years...........
Regards,
Sipke de Wal
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http://xgistor.ath.cx
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----- Original Message -----
From: "Patrick Finnegan" <pat_at_purdueriots.com>
To: <cctalk_at_classiccmp.org>
Sent: Wednesday, October 30, 2002 10:38 PM
Subject: Repairing devices
> I know this is a bit OT, becuase it's not really computer related, but the
> hardware is at least 23 years old, so that's my excuse for posting to the
> list...
>
> I've got a 35mW HeNe Laser + Power supply that I picked up today for next
> to nothing. It seems to be having some problems - the laser (somtimes)
> blinks a few times when I first turn it on, and then stops. From the
> sound of the power supply it's either a loose connection (which I doubt
> after opening it up and taking a good look around) or there's a problem
> with the power supply.
>
> Now, I've never really worked on a HV power supply before, and I'm trying
> to be careful when I play with things. First off, does anyone have a
> general idea of what sized dummy load ("resisitor") I should try haning
> off of the HV output to properly load it? I noticed that the laser tube
> has 3x27kohm resistors in series, would a couple watt approx 81kohm
> resistor be a good idea?
>
> Also, does anyone have an idea for a failure mode to look for? I've got
> an O'scope, dmm, and various other tools at my disposal, but no
> 'authentic' HV test/mesurement gear.
>
> I'm just looking for general guidelines.
>
> Thanks!
>
> Pat
> --
> "The Microsoft/IBM FORTRAN was adequate for teaching FORTRAN 77. But the
> performance was AMAZING! It could actually take longer to run a benchmark
> like sieve of Erastothanes with compiled FORTRAN than with interpreted
> BASIC."
> -- Fred Cisin (XenoSoft)
> http://dilbert.com/comics/dilbert/archive/images/dilbert2040637020924.gif
>
>
Received on Wed Oct 30 2002 - 16:20:00 GMT
