I wanted to reduce the noise from my Sony stereo used as selctor/preamp/remote for my amp and went on servicing and adding some capacitors. All that is not what this thread is about.
Finding that the mains connector is very near the audio circuits, I put a flexilble pcb as shield between the audio board and the mains connector. I don't know whether it improved anything in audio signal path but...
The front panel switches were misbehaving. Press function and some other mode will activate like freq of tuner. These misbehaving has totally stopped and I have added only two capacitors across the +/- 7 volts used for analog circuits.
How can the shield be effective in rectifying the misbehaving front panel switches.
Gajanan Phadte
Finding that the mains connector is very near the audio circuits, I put a flexilble pcb as shield between the audio board and the mains connector. I don't know whether it improved anything in audio signal path but...
The front panel switches were misbehaving. Press function and some other mode will activate like freq of tuner. These misbehaving has totally stopped and I have added only two capacitors across the +/- 7 volts used for analog circuits.
How can the shield be effective in rectifying the misbehaving front panel switches.
Gajanan Phadte
You don't say whether the shield you added is earthed and to which circuit section. It's also not clear whether the switches were also misbehaving before you fitted it. Whatever the case, it seems bypassing the audio section supply rails fixed the problem? Was the switching erratic before you began to modify the Sony amplifier?
I don't think PCB copper foil will block mains hum at the low mains impedance but it seems to me like there is a ground issue for the control circuitry which will be CMOS. This is quite sensitive, very high impedance circuitry and most likely using a separate ground to the audio circuits. It could be worth checking the switching section's grounding and bypassing to see if it is still intact.
Your success with adding the capacitors across the analog power rails suggests there is interaction between the circuits and that may be the problem you are trying to resolve.
I don't think PCB copper foil will block mains hum at the low mains impedance but it seems to me like there is a ground issue for the control circuitry which will be CMOS. This is quite sensitive, very high impedance circuitry and most likely using a separate ground to the audio circuits. It could be worth checking the switching section's grounding and bypassing to see if it is still intact.
Your success with adding the capacitors across the analog power rails suggests there is interaction between the circuits and that may be the problem you are trying to resolve.
You don't say whether the shield you added is earthed and to which circuit section.
I connected the copper to the gnd of the audio pcb I was shielding.
I was trying to reduce the noise from Sony into the amp and was not attending to the misbehaving switches as the remote was working fine.
Gajanan Phadte
I connected the copper to the gnd of the audio pcb I was shielding.
I was trying to reduce the noise from Sony into the amp and was not attending to the misbehaving switches as the remote was working fine.
Gajanan Phadte
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