Electronic schematics, circuit designs
Nokia 3310 service guide manual
Nokia 3310 / 3310 repair hints - download
Nokia 3310 disassembly and component handling - download
Another repair hints for Nokia 3310 - download
Service software guide - download
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Digital bike tachometer
This digital tachometer for bikes uses two reed switches to get the speed information of the bicycle. The reed switches are installed near the rim of the wheel where permanent magnets pass by. The permanent magnets are attached to the wheelspokes and activate the reed switches everytime they pass by it. The speed is digitally displayed.
The tachometer circuit works according to this principle; the pulses created by the reed contacts are counted within a certain time interval. The resulting count is then displayed and represents the speed of the bike. Two 4026 ICs are used to count the pulses, decode the counter and control two 7-segment LED display. RS flip-flops U3 and U4 function as anti-bounce. The pulses arrive at the counter’s input through gate U7.
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UHF antenna amplifier
This amplifier circuit is used to amplify TV signals in UHF range. It uses a low-noise transistor and gives 10 to 15 dB amplification in the frequency range from 400 MHz to 850 MHz.
The transistor must be shielded from the input components and in constructing this circuit, the wirings must be as short as possible. For best results, the cable must be directly soldered to the PCB. The circuit should be installed near the antenna and housed in a water proofed case.
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