AGH.. Please help... Capacitor question...

[AznBruin03]

Hey everyone,

This is probably a simple question, but for some reason I can't find it online. Think my lack of sleep is hindering my searching skills. Anyway, does anyone here know why a capacitor may buzz or emit a noise when the amplitude of the signal going through it is increased??? Please help. Thanks

Henry

 

[typersakimoto]

"Capacitors are limited in the amount of electric charge they can absorb; they can conduct direct current for only an instant but function well as conductors in alternating-current circuits. This property makes them useful when direct current must be prevented from entering some part of an electric circuit. Fixed-capacity and variable-capacity capacitors are used in conjunction with coils as resonant circuits in radios and other electronic equipment. Large capacitors are also employed in power lines to resonate the load on the line and make it possible for the line to transmit more power."

they are not absorbing the increased amount

 

[RossGr]

Physicall capasitor consist of two conductors, the plates, separated by a nonconducting material, the diaelectric. If a cap is buzzing one would have to assume that the plates are loose and viberating, perhaps at 120Hz, a common frequency which needs to be filtered.

 

[AznBruin03]

hmm.. thanks for your input guys...

 

[guitronics]

Anything's possible, but I suspect that your 'buzzing' is caused by a transformer.Transformers work on the principle of electro-magnetism.Coils of wire (1 primary,and at least 1 secondary)are magnetically connected with alternating current (no DC!)and their 'turns ratio' and magnetic coupling (core saturation) determines the voltage and current output(s).

The older-style transformers are usually buily with silicon-steel plates,lacquered for insulation,which magnetically couple the coils,and current together.Sometimes these plates, or cores; get loose and vibrate at a multiple of line frequency.(60 hertz).Sometimes the insulation goes bad. Sometimes the mechanical mounting of the transformer (nust,bolts)gets loose.This causes buzz.

Be very careful with capacitors.Depending on their ratings,if you exceed their D.C.W.V.(DC Working Voltage), or A.C.W.V. they can actually explode.

There are capacitors for A.C.(usually motors), and D.C.(most everything else).A D.C. capacitor connected across an A.C. line will usually explode,sending metal shards and chemicals (Dielectric) everywhere.Not a good thing.

When Caps go bad, they sometimes leak, short out,or just quit working.When a D.C. Cap quits,the D.C. becomes less than properly filtered....and A.C. hum is introduced into the circuit.

I've worked on huge tube-type high-voltage amplifiers,and learned the hard way to discharge the high-voltage on the caps(when not plugged in!)with a 1 megohm resistor.When these caps go bad, the A.C. hum is terrible.But the hum actually comes out of the speakers as part of the signal.

 

[Supradude]

good info guitronics, ha ha, i had the pleasure of getting some capacitor hum two days ago when i fried my secondary AT PSU... darn thing stopped working and just produced this whiney hum...