Hi, A Behringer A500 amp has the following conditions;
The right channel has a loud thump noise and the led indicators pulse full scale about once per second. This happens if there is OR isn't a audio input present, but only happens when the main gain control is set almost full. I have a circuit diagram. Have replaced the electrolytics C31, C28, C39 and the non-polarized cap C34, but still the same. I suspect the amp IC4b - will replace it when spares arrive. This channel also has a lower audio output than the left channel.
Question is; Can anyone explain the bias pots adjustment procedure. I have not touched the pots, but would like to know what voltages at what points, should be measured when the pots are set correctly.
I also noticed that 2 resistors R71 and R72 are shown (voltage divider) in the diagram, but are not fitted on the board.
Any help will be greatly appreciated. Thanks
DigAudio
The right channel has a loud thump noise and the led indicators pulse full scale about once per second. This happens if there is OR isn't a audio input present, but only happens when the main gain control is set almost full. I have a circuit diagram. Have replaced the electrolytics C31, C28, C39 and the non-polarized cap C34, but still the same. I suspect the amp IC4b - will replace it when spares arrive. This channel also has a lower audio output than the left channel.
Question is; Can anyone explain the bias pots adjustment procedure. I have not touched the pots, but would like to know what voltages at what points, should be measured when the pots are set correctly.
I also noticed that 2 resistors R71 and R72 are shown (voltage divider) in the diagram, but are not fitted on the board.
Any help will be greatly appreciated. Thanks
DigAudio
This amp is now back to its former glory! Replaced the op-amp (SMD) and problem solved. Much happiness!!!
Hi
I have the same issue in channel B . I have ordered replacement 4580M op amps . I'll keep you posted on how it turns out .
I have the same issue in channel B . I have ordered replacement 4580M op amps . I'll keep you posted on how it turns out .
I injected 1KHz into the RCA input , and used a scope to trace the signal. I Only got to IC4(b) 4580M op amp, The output had gone high (+15V DC) . Replaced it and now is working well.
I injected 1KHz into the RCA , traced it with a scope , found IC4(b) 4580M Op amp had gone high (+15v) . Replaced it an now it's working well
@rossgo - how hard was it to replace the 4580M opamp? Which one did you get?
We blew one of the 4580s on the channel 1 XLR/TRS input stage. RCA input still works.
We blew one of the 4580s on the channel 1 XLR/TRS input stage. RCA input still works.
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