Wybron PSU clicking noises

[chris325]

Hi all,

We have a Wybron Forerunner-Nexera PSU here that is only sending signal intermittently, and although it should be silent like our other one it now makes a loud clicking noise whenever it's powered on. A bit of disassembly has allowed me to trace the noise to what I think is the ballast.

Any advice/suggestions on how to proceed would be much appreciated. Thanks!

 

[JD]

Red herring. What you have circled is the power transformer. It operates at a high frequency which is why it is fairly small. The power supply is a switch-mode supply. The click you are hearing is because the unit is cycling. Switch mode supplies cycle like that for two reasons:
1) if there is no load on it and therefore only intermittent drive is needed to keep the rails at proper voltage.
2) If there is a short on the output (or in the supply) and it is cycling into protect mode every time it tries to start.
The next step in diagnostics here would be to figure out what is different about the load on the supply. At this point, I believe the supply is just the messenger that there is a problem. Usually switch-mode supplies are quiet. The clicking noise itself is not the problem, just a mode they go into when there is a loading problem. The transformer is where you will always hear the click.
If you have eliminated all problems outside of the supply, then I would suspect a shorted secondary diode or capacitor, or an open fusible resistor or other fuse type device.