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Originally Posted by Dave.W probably relate to UEM... |
That man is right any scratching sounds are ( power hazards ) in origin and cuaes are so many and strange .
-because audio circuits depends on signals not current as logic they use decoupling capasitors to the I/O terminals , if any of the input cap has cracking , falieur ,or even dirty across its pins it gives "Scratching " .
-surge of the DC power or any problem with the power feed , or DC smoothing gives ( audible spikes ) , thats why " Dave " see that it is the UEM .
-Faulty PCBs gives the same ( audible spickes ) , when PCB trackes looses insulation betwwen +ve and -Ve lines due to prolonged heating ( under PA , Light divers and other devices causing heat ). it was common in 3310 faulty PCB with Lights and soundes .