Capacitor buzzing

[jestaudio]

Got a buzz coming from the filter board on a amp build i,m doing, i have disconnected everything from the dropping string and am getting a small buzz similar in sound to arcing contacts, i have no smaothing cap on the diode rectifier, coulkd this cause a problem

[Super_Reverb]

I always thought the smoothing cap across a PS diode was to squelch the broadband noise generated when the diode first turns on. Buzzing sounds like a low frequency phenom.

BTW, if you do use a snubber across your diodes, make sure you use a good quality cap: I had a .01u in series with a 10k across a PS diode and the cap shorted and the snubber resisitor vaporized.

rob

[Structo]

Take a wooden dowel and hold one end against each cap and put your ear against the other end, acts like a stethoscope.
Old car repair trick.

Could just be a bad cap.

On the other hand, my power transformer on my ODS build buzzes a bit when turned on.
Magnetic Components Twin PT.


Or if you suspect arcing turn the room lights out to see if you can spot it.

[jestaudio]

Take a wooden dowel and hold one end against each cap and put your ear against the other end, acts like a stethoscope.
Old car repair trick.

Could just be a bad cap.

On the other hand, my power transformer on my ODS build buzzes a bit when turned on.
Magnetic Components Twin PT.


Or if you suspect arcing turn the room lights out to see if you can spot it.

I,ve used that a few times on cars with a long screwdriver. lol. I'll pull the caps one at a time and see if one of them is duff

[jestaudio]

Ok, after pulling each filter cap i,ve done a bit of investigation, i changed the rectifier diodes and powered up with jusst the rectifier conected, got approximatly the right voltage bearing in mind there was no smoothing cap, no crackle sound and no evidence of arcing on the rectifier board, i then added a 33uf 450v cap to give a bit of smoothing on the dc, immediatly i got a cracking sound, voltages are stable at around 450 ish unloaded.
I assume that the cap will add a small load on the transformer, i suspect the transformer is the problem, further evidence that backs this up is signs on overheating on the filament centre tap, the transformer is one i pulled from a dead amp which tested ok using a dmm but looks to be arcing at the slightest load.
If anyone can suggest a some simple tests which may confirm this i would be gratefull

[Structo]

Maybe someone else has a better idea but maybe a 60w light bulb as a load on the heater winding?

But I think just by doing what you have done, pretty much says that PT is toast.