Switchboard CB 935 alarm fault. - UK Vintage Radio Repair and Restoration Discussion Forum

OscarFoxtrot · 2nd Jun 2015, 11:07 pm

I have a Switchboard CB 935 3+9.

The alarm buzzer sounds continuously.

It ceases if I throw any one or more of the Night Extension keys up, or if I disconnect the wire from the indicators' mounting frame to the buzzer.

All the dolls'-eyes drop satisfactorily and make/break contact to activate the alarm. I don't know if the drop-flaps are supposed to activate the alarm; they don't when dropped.

Is the first place to look for a short somewhere between an indicator and the frame? Or is it likely to be in the night extension keys, which otherwise seem to work correctly, and the alarm works correctly for non-night extensions?

2nd Jun 2015, 11:07 pm	#1
OscarFoxtrot Heptode Join Date: Apr 2011 Location: Edinburgh, UK. Posts: 805	Switchboard CB 935 alarm fault. I have a Switchboard CB 935 3+9. The alarm buzzer sounds continuously. It ceases if I throw any one or more of the Night Extension keys up, or if I disconnect the wire from the indicators' mounting frame to the buzzer. All the dolls'-eyes drop satisfactorily and make/break contact to activate the alarm. I don't know if the drop-flaps are supposed to activate the alarm; they don't when dropped. Is the first place to look for a short somewhere between an indicator and the frame? Or is it likely to be in the night extension keys, which otherwise seem to work correctly, and the alarm works correctly for non-night extensions?