Service manual

13
I nput Volt a g e
The voltage applied to each input should not exceed the supply voltage or damage will
eventually result. If the voltage from the channel switch is more than 5 volts then a couple
of resistors are needed on each input to reduce the voltage seen by the Eprom. Some
channel switches do not supply a positive voltage but ground the inputs, instead. Where
this is true you must connect a resistor between each switch connection and the 5 volt
supply to the Eprom. You could even introduce this method yourself where the channel
switch voltage is high. Simply remove the supply wire from the switch common
terminal(s) and ground the switch common. Now you need only half the number of
resistors. The switch codes will all be inverted, of course but, since they are simply
SELECTING Eprom locations this hardly matters, provided YOU know what the codes
are!