So i'm currently attempting to revive a Pioneer A676 Amp. I'm getting no sound out of the speaker terminals or headphone jack and no relay clicking. The amp does appear to be powered up (got LED's on the driver boards although no power light - I think its just the bulb burned out tho!) The other lights come on when the buttons are pressed ok.
I've got 70mv DC on the output of both the driver boards AWZ3421 and AWZ3418 and if I feed in some sound to the input jack and connect my scope to each output from the amp boards (Left + Right) I can see the amplified sound on my scope and I can adjust the volume using the volume control. So it seems as if the amplifier circuitry is all working and its taking the signal and amplifying it. But something isn't happy and it isn't allowing the relays to turn on. I've pulled each of the relays out and manually checked them and they are working normally.
I've been looking carefully over the service manual and have found something - i've got no 13.2V or 13.3V on the VR Assembly board AWZ3441 and instead am seeing between 0.45 and 0.6V there - I cannot however seem to get my head around where this voltage is supposed to come from and was hoping someone with a bit more experience on this amplifier to point me in the right direction for what I can check next. I believe that without this voltage the relays are not going to activate.
Just as a quick update/edit - I decided since there was no noticeable DC on the amp output I wired a speaker up to the output before the relay (i've tried both channels) and the amp works perfectly sounds clear and all other functions work - volume control etc. Obviously this is not a solution but it confirms the amplifier is working correctly.
I've got 70mv DC on the output of both the driver boards AWZ3421 and AWZ3418 and if I feed in some sound to the input jack and connect my scope to each output from the amp boards (Left + Right) I can see the amplified sound on my scope and I can adjust the volume using the volume control. So it seems as if the amplifier circuitry is all working and its taking the signal and amplifying it. But something isn't happy and it isn't allowing the relays to turn on. I've pulled each of the relays out and manually checked them and they are working normally.
I've been looking carefully over the service manual and have found something - i've got no 13.2V or 13.3V on the VR Assembly board AWZ3441 and instead am seeing between 0.45 and 0.6V there - I cannot however seem to get my head around where this voltage is supposed to come from and was hoping someone with a bit more experience on this amplifier to point me in the right direction for what I can check next. I believe that without this voltage the relays are not going to activate.
Just as a quick update/edit - I decided since there was no noticeable DC on the amp output I wired a speaker up to the output before the relay (i've tried both channels) and the amp works perfectly sounds clear and all other functions work - volume control etc. Obviously this is not a solution but it confirms the amplifier is working correctly.
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