Product Overview
Chicago Miniature 120MB T-2.5 Miniature Bayonet Indicator Bulb
Condition
Unused new old stock (NOS). Visual inspection shows an intact internal filament, clear glass envelope, and clean base terminal. Sold individually.
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Product Overview
Chicago Miniature 120MB miniature incandescent indicator lamps deliver steady illumination in equipment wired for bayonet-mount pilot lights. Built with a clear tubular T-2.5 glass envelope and a miniature bayonet base, this lamp provides reliable visual feedback across control panels, annunciators, and instrumentation.
Key Features
- Miniature bayonet base with dual side locking pins and single center contact
- Clear tubular glass T-2.5 envelope
- Coiled internal filament with dual support wires
- 28 mm overall length
- Standard fit for miniature bayonet indicator sockets
Applications
- Maintenance technicians replacing burned-out indicator lamps in legacy machinery and industrial control panels
- Facility electricians maintaining annunciator displays, status boards, and alarm pilots
- Electronics builders and bench restorers servicing vintage test equipment, audio gear, and custom consoles
Frequently Asked Questions
What base style does this lamp use?
This bulb uses a standard miniature bayonet base (BA9s) with two opposed side pins that push and twist into the socket, terminating at a single bottom center contact.
What are the physical dimensions of the bulb?
The lamp measures 28 mm in total length from the bottom base contact to the top of the glass envelope, with a tubular glass envelope measuring 8 to 9 mm in diameter.
How does this bulb differ from slide-base or screw-base indicator lamps?
The 120MB utilizes a smooth metal barrel with two protruding retention pins that lock with a quarter-turn, unlike flat slide-base telephone lamps or threaded miniature screw bulbs.
Nothing beats the warm, instant glow of a true filament when an indicator panel clicks awake. Keep the board lit and the console running just like the original drawings intended.
