On 14/03/2019 18:41, Jon Elson wrote:
On Thu, 14 Mar 2019 11:04:55 +0000, N_Cook wrote:

TO18 size of can but inerference fit? mounted in a brass mount with
lens, no type number seen.
Actively passing 60mA drops 1.3V and DVM-D test shows 1V one way, so
Is this a laser or just an LED? 60 mA sounds to me like it might be a
laser, and fairly powerful.

1979? Hmmm, probably NOT a laser at that date, and hitting such an old
LED with such current would be pretty hard on it, unless the pulses were
short and the duty cycle low.

Possibly heating the whole assembly might make the emitter slide out.
I doubt these would be interference fit, as that could easily damage the
emitter. Likely, a TO-18 package had a fairly wide dimensional tolerance.
So, I'm guessing they used some kind of glue to hold it in place.

Jon


No type number found, but at least the likely failure mechanism found,
manufacturing flaw waiting to happe, although all well butchered now.
Not a TO18 device fitted to a brass barrel. Heat and freezer spray made
no difference. So decided to dremmel 0.5mm grinding disc a slot in the
brass to relieve the pressure. Firstly it was gold plated copper , not
brass and no TO18 device, just a ring of something containing brown
epoxy and the pins , so looking like TO18 can.
The GaAs die .4mm or so square sitting on plated Cu "top hat"
heatsink/plinth, inner diameter of 10mm and outer diameter of 15mm.
Interference fit to that ledge, dislodged in trying to force open the
slot in the copper, machined Al barrel 13mm long. Machined to a cone
inside with pin-hole at end, taking an unsupported length of bare fibre
optic approx 8mm long, presumably was cemented to the die.
Then a lens fitted over the other end of the fibre over the outer end of
the internal cone.
So with resonant mechanical vibration from carriage at some point ,
thermal or g-shock stress , or just post fibre manufacture internal
fibre stress-relief over time, the fibre could break from the die and
end up 0.2mm off-axis , so IR in the cone recess and next to none in the
fibre,so to the outside world no optical output.
As no make/number perhaps an early run, just post prototype, before
someone twigged the built in self-destruct design flaw.