I have an old Denon DCD-425 CD player which I would like to upgrade by removing the muting transistors and replacing them with relays.
So far, with the help of my scope and eyeballs, I have discovered a link on the PSU board labelled "mute" this is connected to the main board along with various voltage rails. On the PSU board there appears to be some sort of simple RC delayed transistor circuit which takes the mute connection to approx 3V when muting is required (at power up and any time when there is supposed to be no audio output) and briefly swings slightly below, then back to 0V when playing.
Disconnecting the mute wire that connects the PSU board to the main board has the expected effect of causing a loud power-on thump but otherwise doesn't seem to affect the player (when skipping tracks etc).
I think I have identified the muting transistors but the crazy track layout and liberal use of SMT devices on the track side of the board has left me very confused as to the implementation of the muting circuit.
Any help would be greatly appreciated. Especially a schematic - although I think it's a difficult one to obtain.
Photos to follow...
Regards,
Rob
So far, with the help of my scope and eyeballs, I have discovered a link on the PSU board labelled "mute" this is connected to the main board along with various voltage rails. On the PSU board there appears to be some sort of simple RC delayed transistor circuit which takes the mute connection to approx 3V when muting is required (at power up and any time when there is supposed to be no audio output) and briefly swings slightly below, then back to 0V when playing.
Disconnecting the mute wire that connects the PSU board to the main board has the expected effect of causing a loud power-on thump but otherwise doesn't seem to affect the player (when skipping tracks etc).
I think I have identified the muting transistors but the crazy track layout and liberal use of SMT devices on the track side of the board has left me very confused as to the implementation of the muting circuit.
Any help would be greatly appreciated. Especially a schematic - although I think it's a difficult one to obtain.
Photos to follow...
Regards,
Rob