Hello everyone,
Sorry long post!
I have been given a Nakamichi AV-8 receiver (saved from landfill)..
Good news is that it fires up (yay) and works through headphones (double yay) but there is not output to the speakers. There is no obvious component damage to the output stage. The display, switching logic and the output stage cooling fans fans are working. There's a clunk from one (or more) of the speaker protection relays when the unit is powered down and also if the A and B speakers are pushed on / off.
Bad new is that it's a nightmare to work on and I haven't managed to track down a service manual for it yet (although I do have a AV-10 service manual which I may be able to get by with). The output stage is arranged as a 'removable' rectangular box. There is no removable service panel beneath the main board which unfortunately I think is the location of my problems.
After an hour I had the entire unit stripped down (only way to get the main board out to inspect underneath) and observe a pair of DC rectified circuits which lead off to the protection circuit (and other things). There has been a fair amount of heat in this area (tell tale browning) and the dry joints beneath were glaringly obvious.
The challenge for me is that the entire device has to be fully reassembled again before it can be tested. After de/resoldering the area and reassembling the whole unit, good news id it's no worse, not so good is that it's no better.
I'm grateful for the AV-10 manual I have downloaded from Hi-Fi Engine but would feel more comfortable with a copy of the AV-8 manual if I can get hold of one.
Any suggestions appreciated (it's off the bench at the moment)
Ciao Blake
Sorry long post!
I have been given a Nakamichi AV-8 receiver (saved from landfill)..
Good news is that it fires up (yay) and works through headphones (double yay) but there is not output to the speakers. There is no obvious component damage to the output stage. The display, switching logic and the output stage cooling fans fans are working. There's a clunk from one (or more) of the speaker protection relays when the unit is powered down and also if the A and B speakers are pushed on / off.
Bad new is that it's a nightmare to work on and I haven't managed to track down a service manual for it yet (although I do have a AV-10 service manual which I may be able to get by with). The output stage is arranged as a 'removable' rectangular box. There is no removable service panel beneath the main board which unfortunately I think is the location of my problems.
After an hour I had the entire unit stripped down (only way to get the main board out to inspect underneath) and observe a pair of DC rectified circuits which lead off to the protection circuit (and other things). There has been a fair amount of heat in this area (tell tale browning) and the dry joints beneath were glaringly obvious.
The challenge for me is that the entire device has to be fully reassembled again before it can be tested. After de/resoldering the area and reassembling the whole unit, good news id it's no worse, not so good is that it's no better.
I'm grateful for the AV-10 manual I have downloaded from Hi-Fi Engine but would feel more comfortable with a copy of the AV-8 manual if I can get hold of one.
Any suggestions appreciated (it's off the bench at the moment)
Ciao Blake
Do you know if the headphone output derives from the main output stages? If it does then the problem must be in the speaker protection circuit/relay, output fuses, output wiring or similar.
If the headphone output doesn't come from the main amp output, then the main amps could be down, lacking power, disconnected, etc etc.
Is there any DC offset at the outputs?
If the headphone output doesn't come from the main amp output, then the main amps could be down, lacking power, disconnected, etc etc.
Is there any DC offset at the outputs?