Soundcraft Europa - Relay Ticking

[smilan]

Hi, I'm trying to repair a Soundcraft Europa.
As soon as I'm turning on the PSU RL2 at the SWITCHED PSU DISTRIBUTION PCB start to ticking.
The relay itself have some over heating marks on it's body (I believe that due to the heat that the mechanical movement create).
Does a faulty diode (D9) will make the relay act like this?

 

[ccaudle]

Does a faulty diode (D9) will make the relay act like this?

No, the diodes across the relay are just to clamp the voltage across the coil. When you suddenly stop current flow through a coil the voltage across the coil rises quickly, and can become high enough to damage the switching transistor if an alternate current path is not provided back to the other end of the coil.

Likely when the relay is engaged something happens which causes the relay driver to drop out, perhaps a load which is too high (e.g. short circuit downstream) which causes the relay to turn off, which removes the load on the power supply which allows the power supply to come back up, which turns on the relay again, which causes the power supply to drop and turn off the relay, etc.

 

[smilan]

No, the diodes across the relay are just to clamp the voltage across the coil. When you suddenly stop current flow through a coil the voltage across the coil rises quickly, and can become high enough to damage the switching transistor if an alternate current path is not provided back to the other end of the coil.

Likely when the relay is engaged something happens which causes the relay driver to drop out, perhaps a load which is too high (e.g. short circuit downstream) which causes the relay to turn off, which removes the load on the power supply which allows the power supply to come back up, which turns on the relay again, which causes the power supply to drop and turn off the relay, etc.

Thanks, I'll try to disconnect all the load (channels) from the main board and bring them back one by one and try to identify the faulty one.

 

[Newmarket]

Doubt it. Omitting the diode results in inductive "kickback" at turn off. Usually resulting in the turn off action bouncing around a bit (excuse the tech jargon ) and an audible "fuzz". Not good for the relay contacts over time but not what you are experiencing.
Suggest monitor the supply voltage there with a 'scope.