The radio was purchased after a quick power-up test, which produced a healthy loud white noise and all displays lit up. However, when the radio was powered up at home, there was no audio. Although all displays appeared to be working well, the S meter showed full deflection.
using a sniffer amplifier to probe the input pin 1 at IC5 (uPC2002v
audio amplifier chip) it was noticed that there was goo around the
base of electrolytic capacitor C104.
C104, a 470uF electrolytic capacitor, had catastrophically failed, causing the electrolyte material to blow out from the bottom of the capacitor and onto the PCB (Printed Circuit Board). The damaged C104 capacitor was replaced, and the electrolyte material was thoroughly cleaned from the board. However, the electrolyte had reacted with the green PCB mask, resulting in complete deterioration of the mask under the capacitor and leaving the exposed copper after cleaning.
There is a reasonable concern that the electrolyte material would have ultimately corroded the copper PCB tracks.
After replacing C104 and thoroughly cleaning the electrolyte material, related electrolytic capacitors C99 and C101 were also replaced as a matter of opportunistic preventive maintenance while the board was out.