Uploaded January 2017 | Updated September 2026, 1 week ago
Unit had irritating thump when the bass control for left channel was turned. All 8 electrolytic capacitors on the tone control board were replaced. A smaller thump still remained, which mystified me. I then connected the output from the tone control board of the left channel to the right channel input of the main amp board. Both the left and right channel inputs to the main channel were disconnected beforehand. The thump went away; this led me to conclude that the remaining thump was caused by a component in the original left channel on the main amp board. Replacing the first component the signal went into on the main amp board, a 1 uF electrolytic capacitor, solved the problem. The right channel capacitor was also replaced.
The following capacitors were replaced:
1. Tone Control board
2 each 0.47 uF electrolytic capacitors rated at 25 volts.
2 each 1.0 uF electrolytic capacitors rated at 25 volts.
2 each 100 uF electrolytic capacitors rated at 6 volts.
2 each 47 uF electrolytic capacitors rated at 50 volts.
2. Main amp board.
2 each 1 uF electrolytic capacitors rated at 25 volts.
Unit had irritating thump when the bass control for left channel was turned. All 8 electrolytic capacitors on the tone control board were replaced. A smaller thump still remained, which mystified me. I then connected the output from the tone control board of the left channel to the right channel input of the main amp board. Both the left and right channel inputs to the main channel were disconnected beforehand. The thump went away; this led me to conclude that the remaining thump was caused by a component in the original left channel on the main amp board. Replacing the first component the signal went into on the main amp board, a 1 uF electrolytic capacitor, solved the problem. The right channel capacitor was also replaced.
The following capacitors were replaced:
1. Tone Control board
2 each 0.47 uF electrolytic capacitors rated at 25 volts.
2 each 1.0 uF electrolytic capacitors rated at 25 volts.
2 each 100 uF electrolytic capacitors rated at 6 volts.
2 each 47 uF electrolytic capacitors rated at 50 volts.
2. Main amp board.
2 each 1 uF electrolytic capacitors rated at 25 volts.
