"N Cook"

http://home.graffiti.net/diverse:graffiti.net/prot.jpg

The thermal switch monitors the heatsink but what is the function of the
depletion type FET, monitoring the negative half cycle of the the AC3 ac
line, via D3 ?


** Switch on delay - then un-mute the loudspeaker.

AKA an anti * THUMP * circuit.


What happens in a fault mode to that line that can be
monitored and could be of use for protection.operation?


** Only if FS1 blows.


What does D1 do ?


** Fast discharge of C5 - so a quick off for the relay when AC supply
removed.

Another anti-thump function.


The relay contact cuts in serious attenuation of the signal going to the
pa
in fault mode


** There is no fault protection in that schem.



....... Phil



--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/