Heater*Filament*Power*Cables*
!
Connect! the! 6.3V! and! 0V! from! the!power! transformer! secondary!(Sec2:! 2A)! to!
the!filament!power!supply!PCB!as!shown!in!Figure!21!-!Two!cables! (red!and!black)!
connecting! power! transformer! secondary! terminals! (6.3V,! 0 V)! to! the! filament! power!
supply!PCB.!!
!
!
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Now! we! will! supply! the! heater! filaments! with! the! 6.3VDC! from! the! heater!
filament!power!supply!board!to!the!H1!and!H2!terminals!on!the!amplifier!boards.!!
!
Do!the!following:!
!
1. Connect! the! filament! power! cables! –! from! the! filament! power! supply!
board! to! each! of! amplifier! boards.! Note! there! will! be! four! cables!
altogether!for!this.!Two!positives!and!two!negatives!(a!pair!of!positive!and!
negative!to!each!board).!If!you!refer!to!Figure!22!-!Green!cable!connecting!the!
0V! terminal! on! the! filament! power! supply! PCB! and! the! star! ground! point.!
properly,!you!will!see!that!there!is!a!bunch!of!cables!wrapped!up!in!the!
black!heat!shrink.!There!are!4!cables!(two!reds!and!two!blacks)!altogether!
in! this! bunch.! Each! of! the! black! and! red! pair! is! carrying! the! DC! power!
from! the! filament! power! supply! board! to! the! two! amplifier! boards!
(terminals!are!labeled!as!H1!and!H2).!Refer!to!the!wiring!diagram!again!to!
make!sure!that!you!fully!understand!the!wiring!
2. Ground!the!negative!terminal!of!the!filament!power!supply!board.!This!is!
done!by!connect ing!the!0V!OUT!terminal!to!the!star!ground!(check!Figure!
22!-!Green!cable!connecting!the!0V!terminal!on!the!filament!power!supply!PCB!
and!the!star!ground!point.!and!note!the!green!cable).!!
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