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Frequency Counter LS-223 ( Home brew )

[Outline] [Front view] [Top view] [Bottom view] [Block diagram]

[Pre-amplifire, pre-scaler and 10MHz clock osccilator]
[5V AVR pwb and capacitors for power supply]
[BCD to decimal converter (nixie tube driver)]

Fig.1 Pre-amplifire, pre-scaler and 10MHz clock osccilator

Fig.1 shows pre-amplifire, pre-scaler and 10MHz clock oscillator.

Pre-amplifire for TTL input is consist of 1 FET and 3 bipola transistors direct coupled. The ground plane is removed around FET input to reduce stray capacitors.

Hitachi HD10551(ECL with pre-amplifire to ECL and level converter from ECL to TTL ) is used for the 1/10 pre-scaler.

A miniture relay is used to switch the input signal to dilect input and prescaled input.

A 10MHz crystal , an air variable condenser, 3 transistors are used for clock oscillator.