Author
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Topic: Lamp query
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David Pannell
Phenomenal Film Handler
Posts: 1072
From: Horsham, West Sussex, UK
Registered: Nov 2004
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posted July 14, 2005 08:58 AM
Hi,
Not true!!
Any simple continuity meter is absolutely fine for checking lamps. The current is so small that there is no way it can damage the lamp.
As for a damaged filament - hardly. If the filament is broken a test will show it as open circuit, not partially so. A lamp filament will either be healthy or not - nothing in between.
I would go for Winbert's diagnosis 110%. Oxidisation - or rather dirt/contamination on the pins. However, I don't think I would use glass, sand or emery paper for cleaning, as often the pins are silver plated, and this would remove the plating. I would go for an electrical solvent switch or contact cleaner, such as Super Servisol or similar. Silver plated pins are used due to the excellent low contact resistance which it provides, thus helping to keep the lampholder cool whilst transferring maximum power to the lamp.
BTW, - a fine point here, - silver oxide is a conductor of electricity, so it's not the actual oxidisation of the pins causing the problem, but the atmospheric dirt and grime over the years which attaches itself to the silver oxide.
Dave.
-------------------- Dave.
Valves and celluloid - a great combination! Early technology rules OK!
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