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EXPRESSION UPGRADE BOARD
Make sure there is no pin jumper installed on the main board at TUNER JMP. Now let’s assemble the
expression board.
1. Ceramic Capacitor (C25): Install the 100nf (.1uF) ceramic cap in its place on the face of the board
(117); bend the leads on the back of the board; solder and clip the leads.
117
2. Zener Diode (D2): The 5.1V Zener diode is used to protect the digital potentiometer from being
subjected to excessive voltage. The digital pot shouldn’t have much more than 5 volts on its pins,
so any voltage on the expression jack over 5.1V will be shunted to ground via this Zener diode.
This diode is polarized. The black stripe indicates the lead that goes into the hole with
the square pad. The other (non-striped) lead must be bent and placed into the round pad.
BLACK STRIPE = STRAIGHT = SQUARE PAD
NO STRIPE = BENT = ROUND PAD
Bend down the lead WITHOUT the black stripe until it is about parallel with the diode body (118).
Slide the Zener diode into its location on the board with the black stripe against the square pad
(119,120). Bend the leads out on the back. Solder and clip the leads.
118
119
120