8mm Forum: Filmosound Optical Lamp

This is topic Filmosound Optical Lamp in forum 16mm Forum at 8mm Forum.

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Posted by Brian Collins (Member # 761) on December 04, 2011, 12:26 PM:

Hi I am using my Bell & Howell Filmosound 644 and the optical lamp is not lighting up. Have done a continuity test on the lamp and that shows it is OK, is there a fuse for this or have I to look for some other fault? have moved the top lever to sound if that has any bearing on it,any help appreciated.

Posted by Pasquale DAlessio (Member # 2052) on December 04, 2011, 04:04 PM:

Brian

Check for voltage at the contact points in the lamp socket.

PatD

Posted by Brian Collins (Member # 761) on December 05, 2011, 03:08 AM:

Pat
No voltage at all, so will have to investigate why.

Posted by Simon McConway (Member # 219) on December 06, 2011, 05:40 PM:

According to the service manual, check the rectifier. Having never attended to such a fault on this machine, I'm not fully sure of the details you'll need, but I'm presuming this will be at the base of the machine, in the amplifier board. Trace the wires back from the exciter lamp and you'll see a rectifer of either the bridge type, or single diodes. Check these out, if the wiring proves okay.

Posted by Brian Collins (Member # 761) on December 08, 2011, 10:40 AM:

Thanks Simon, I have had to shelve the job for the time being but will certainly check what you advise when I get round to it again.

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