Preamplifier scanner
This circuit scan all the preamplifier entries to identify where is a audio signal and that entry remains selected. After a sign of signal absence, scanning resumes. Scanning action is supported by rectangular signal generator IC2c. Scanner’s entries are connected to the audio entries from volume control board of the preamplifier.
Useful signal is amplified by 40 times with IC1c and IC1d, then summator amplifier IC1a combine left and right signals. As soon as a signal of music or vocal appears on entry lines, C1 partialy discharges, very quickly. As long as it receives the input signal, a part of the capacitor C1 load is
Read the rest of this entry »
CGA / SCART adapter
CGA adapter / SCART has great advantages as it does not require separate power source and that uses very few external components, which can be easily adapted in the SCART connector. The signals from R, G and B pins of the CGA’s board are converted from TTL levels to SCART levels with resistors R4, R5 and R6 and entry’s impedance (75 Ω) of scart inputs.
Output Impedance of voltage dividers thus created is not exactly 75 Ω as specified for SCART inputs, but in practice the behavior seems to result not big differences.
Read the rest of this entry »
Pb and acid batteries charger
Modern acid batteries and plates Pb, are embodiment of simplicity in use. Unlike NiCd batteries, they must be recharged by connecting to a constant voltage. In this situation, the loading current will provide a good indication of the state of loading.
These batteries can be quickly loaded as long as the loading current is limited even at the beginning of the trial proceedings. The charger which we propose it has a
Read the rest of this entry »
