The Aussie Pinball Arcade
Aussie Pinball Forums => Technical Matters => Pinball Repairs / Problems & Assistance => Topic started by: pinball god on December 27, 2008, 10:29:08 PM
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This is not so much a problem but interested in the answer. Pulled out a #555 today and noticed it had a nice chrome effect near the filament. Had these before. What causes this? Is there any need for concern? Is there something that can be done? Or is it just a dud globe?
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I've seen this type of globe a few times. Either black or a chrome silver. Not sure of the technical reason why it happens, but I consider them "dud globes" and discard them. If the problem persists on that one socket - then the issue would be the socket.
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Its caused by the filament slowly breaking down - known as the Edison Effect.
Electrons leave the filament and end up coating the inside of the glass. Eventually, the filament gets too thin and breaks - majority of it is lining the glass.
Its mainly caused by poor processing at manufacture, impurities are left within the globe itself and cause this to happen. It also causes the vaccuum inside the globe itself to dissipate, leading to further resistance and heat, and therefore further break down of the filament. Its a cycle that eventually kills itself. These "chromed"globes will be running hotter than a new clean one
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You can also "chrome" a bulb by applying too much voltage. I have experience with this during the early days of Nucore
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I pulled a bunch of 'chromies' outta my Stellar Wars a few weeks ago.
Any globes that are dark/black/chrome are about to cause trouble.
Also note, globes that run dark or chrome run HOT, and will take your fingerprints off nicely.
Be careful !
MM.
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great advice guys.