Advice on silencing power supply noise

[joshzstuff]

Below is the patient.

The high frequency noise is coming from the area I circled. It is not extremely loud, but I can hear it in a quiet room.

I know that some PC computer supplies will 'whine' when taxed by heavy graphics processes, however my noise problem is the reverse, it 'whines' UNTIL it is placed under load.

Power specs:
The Power supply is a 5volt charger powering my Picaxe controller and a small total load of ~300-400ma Or another circuit could take it close to a full Amp in total current (well within the supplies limits)

The noise seems to me to be emanating from the blue 1nF 1KV ceramic cap.
At least that is what I think it is. The markings are:

B
102K
1KV

Possible solutions:

I'm interested in any high or low tech solutions you may know of.

-I read that when the inductor or chokes whine you can coat them with nail polish or other substances. I'm not sure if that would help here.

I have 2 Power Supplies, so I can experiment on one of them, but since they both have the same noise from the same general spot, I'm inclined to dismiss manufacture fault. (I.E. re- soldering components)

Thanks!

 

[(*steve*)]

Get a blob of glue and use it to stop the component vibrating. This is less effective at higher frequencies than at low ones.

It's quite possible that at very low loads the frequency of operation is lower (and thus audible). The frequency may increase as the power supply moves out of discontinuous mode and the sound (whilst still present) simply cannot be heard.

 

[davelectronic]

Ive had switch mode psu's wine on low or no load the majority are poor quality and build, invest in a better cleaner supply or build your own, easy.

 

[joshzstuff]

Get a blob of glue and use it to stop the component vibrating. This is less effective at higher frequencies than at low ones.

It's quite possible that at very low loads the frequency of operation is lower (and thus audible). The frequency may increase as the power supply moves out of discontinuous mode and the sound (whilst still present) simply cannot be heard.

Hmm, Steve interesting theory . . .
That would explain why it is only audible with less load!

I'll try some hot glue.
If that doesn't work, any caveats to upgrading to an epoxy?

I'll try it and get back with the results.

 

[joshzstuff]

Ive had switch mode psu's wine on low or no load the majority are poor quality and build, invest in a better cleaner supply or build your own, easy.

I'm afraid my best option is to make this one work as I an not as experienced as you are.

Also, I have space requirements (which was a major factor in choosing this model) so I'm sure that even if I were successful at a quality supply, the finished result would be much larger.

Perhaps this is a project I will tackle when I'm a little more experienced.

 

[(*steve*)]

Hot glue is probably a reasonable thing to try. The capacitor doesn't look like something that will get too hot (so you're unlikely to make it overheat by limiting ventilation)

Try not to cover any of the identifying data on the components just in case you need to replace it.

edit: the problem with epoxy is that it may be too permanent.

 

[D_Hambley]

Try sqeezing on the transformer vertically while it's running. If the sound changes when you do this, it could be the transformer which is singing.

 

[(*steve*)]

But be very careful. The transformer may be at mains potential and I'd hate to think you received deadly advice...