A simple question about - Bulbs

sooty · Unread post by **sooty** » 19 Dec 2003, 23:27

A simple question, what causes bulbs to go black after a short time ie: tail lamp ?? A fault or quality of bulb.
Sooty

Kered · Unread post by **Kered** » 20 Dec 2003, 01:31

Bulbs go black as the tungsten filament "boils off" as a vapour and is then deposited on the glass as a dark stain. So the black was once part of the filament. The tungsten is glowing white hot in order to give the needed light. IF it goes black in a short space of time it is most likely that the applied volts are too high - so running the filament at a higher temperature than is desirable causing premature blackening. Cheap bulbs could be so poorly specified that they blacken at normal volts.
Derek

AndersDK · Unread post by **AndersDK** » 20 Dec 2003, 01:55

Agree with Derek - a common problem with cheap lo quality bulbs.
Stick to wellknown branded bulbs - they are not that more expensive.
Often the gas stations offers lo quality bulbs at insanely high cost - as you don't walk around town just to find a simple replacement bulb.