I’ve had a Sony CDP-790 since the 90s and it’s been working fine. I’ve recently taken it to the heat and dirt of the Italian countryside and it has started to show its age a little. It recently wouldn’t read any cds so I cleaned the laser and the microswitches and reassembled. Now it reads and plays fine but I seem to have introduced another problem – it will not eject cds. My current getaround is to operate the cd drive on a board on top of the machine, so that when I want to change cds it’s a relatively easy (but hugely irritating) dismantling to remove one and replace with another.
- The tray will insert smoothly when it is open. It does not eject.
- Both the microswitches appear to be working. I can nudge the ‘closed microswitch’ to stop the tray insertion process. I can ‘nudge’ the ‘fully open microswitch’ to stop the TOC reading.
- When I press eject (or use the remote) the tray motor does not turn (under any circumstance, even if I’ve removed the belt to lessen its load. Instead the machine reads the toc, displays the results (number of tracks and total time) and then (after a couple of seconds) displays ‘track 0’
- Similarly, after playing a cd the machine will display ‘track 0’. As far as I recall, this is not what it used to do: after playing a cd it would display the number of tracks and total time until the cd was removed.
- I have tried disconnecting electricity for a few hours to give the machine time to compose itself but to no effect.
I would check and double check the microswitches particularly as this seems to be an issue that has occurred after the problem of not reading discs.
This thread was all about these players:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
This shows the microswitch configuration:
This thread was all about these players:
https://www.diyaudio.com/community/threads/sony-cdp790-and-kss240-restoration-project.226288/
This shows the microswitch configuration:
Thanks, Mooly. I looked at the forum you mention as one of my first sources for what I've dome so far. I should explain I'm an electronics ignoramus so it will take me a little while to understand the circuit diagram you have helpfully sent. (But I'll try.) Am I oversimplifying things to think that if the 'closed microswitch' is 'on' and the 'open microswitch' is 'off' the drive should start the tray motor to eject the tray?
I never measured the switches but from what I remember they are normally open (when the tray is neither in nor out) and the appropriate switch closes when the tray is at the end of its travel. You would have to measure them on the connector to board on ohms range on a meter to confirm. There is a common ground for both.
The switches do not pass any motor current but simply indicate to the system control IC that the tray is in, out or moving. So I would expect both to be open if the tray is part way out and one or the other to be closed when the tray is in or out.
If you move the tray manually to half in/out and then apply power the default action should always be to close the tray automatically.
The switches do not pass any motor current but simply indicate to the system control IC that the tray is in, out or moving. So I would expect both to be open if the tray is part way out and one or the other to be closed when the tray is in or out.
If you move the tray manually to half in/out and then apply power the default action should always be to close the tray automatically.
Take a look at this guy's actions to get his to behave properly (linked near 7 minute mark). Looks like he is lightly sanding/cleaning some contacts. It's an odd video, but may be of help to you since you've already been inside the unit. Good luck.
Thanks, Mooly and jordheis. I diligently watched the video and tried to copy the diligent sanding and cleaning of the microswitches, as suggested. I reassembled the drive but nothing has changed, I'm afraid. The machine's behaviour is still exactly as described above. What surprises me is that I am able to fiddle about incompetently with the thing and have it still play cds when I reassemble it. I suspect that I'll now be getting into deeper waters than my competence (and lack of test kit) allow. The thing will load perfectly well, stop when closed and play cds. All of that counts as good behaviour. Then when I ask it to eject, instead it reads the toc, bad behaviour I may just have to live with unless anyone has any new avenues to suggest.