GaAs Infrared emitter failure

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 diode function , but no IR out as tested with IR zapper tester of IR photodiode in series with optical LED , indicates on or flashing of any working zappers ever tried with it. So are they known to fail optically, perhaps overdriven, but not go o/c or low ohms , still functioning as a diode though. ? Kit specs say 910nm and no tab seen , but TO-18 can type , although that could be machined off to clear the brass barrel , any machining not seen as axial view only, due to the surrounding brass barrel. So something like SFH400 to 2, FPE500 to 530, OP223,224,231,232,233, or TIL23 to 25 but none of those are specified as exactly 910nm , ranging 880 to 950nm. Initially I will try heating the assembly to 120 deg C and blast of freezer spray to TO18 package , to try breaking presumed assembly-heated interference fit , to split apart. Other than finally drilling out or seriously heating if laquer fit, any ideas to break apart without destroying any marking. Hand scratched on the brass is number 3738 presumably relating to a test of the lens combination or perhaps coding of date in 1978 , as 1979 kit.

Reply to
N_Cook
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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

Reply to
Jon Elson

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.

Reply to
N_Cook

Maybe can be a UV LED !

Reply to
Look165

Specifications in the user manual say IR 910nm and another contemporaneous (1979) source says the same.

Reply to
N_Cook

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