OT: AC to DC transformer source needed

I have an Acra-View Optical Comparator, and the bulb it came with was burned out. Checking around, the bulb was around $14 US. I checked the supply voltage, 9vts AC, so went down to the local auto parts store, and picked up a brake light bulb for a 6 volt system. Works fine, nice and bright and cost $1.89

Gunner

Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

A warning which may not have been included with the packaging for that bulb -- Handle it with clean cloth, or gloves. The natural oils from fingers will etch the quartz envelope of the bulb in the presence of the strong ultraviolet from that filament. It probably came with some kind of sleeve to protect it while you install it.

If you have already handled it -- clean it with alcohol or acetone before putting it into service. I don't know for sure, but I suspect that the bulb's failure mode from this would be to shatter while warming up or cooling off sometime downstream, after the etching has gotten deep enough.

Yep -- you can.

Good Luck, DoN.

This is really good advice. But I would suggest even one step further, which is clean *all* quartz halogen lamps before putting them in to service, if the owner has touched them or not.

I went through a fair number of them rapidly at work, before realizing that the failed ones had fingerprints on them - and I was wearing gloves when they were installed! The failure mode was not terribly dramatic, the gas in the envelope gets contaminated and the interior is darkened and smudged before it simply burns out. I've never had one fail catastrophically.

But ever since I saw the assembler's prints on the burned out one, I always give them a wipedown with ethyl alcohol before installing them. And they seem to last a lot longer. I do the same with qtz halogen auto lamps also.

Jim

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They don't care only to first approximation. AC is generally better.

Check out the excellent photos of filament "notching" in the Transport Canada report.

Those Home Depot type electronic "transformers" that others have suggested sound like the right solution. Or the PC supply kludge (which might be free).

Best regards, Spehro Pefhany

I've had ordinary quartz bulbs fail explosively. These were in

500 to 2000 watt studio luminaries. They sound like a 12 gauge shotgun when they fail. Same reason, fingerprints. The 300 watt quartz work lights from the usual sources fail the same way, though not quite as loudly.

Gary