Transformer Hum?! STOP IT!

[mlloyd1]

Save yourself some trouble and search for the original discussion. We went through all this then.

mlloyd1

...I don't totally understand C1 and C2. With anti-paralled diodes, there should never be more than about a volt across either capacitor...

 

[Elso Kwak]

Pulses on the mains

Sounds like mine, except the humming on mine pulses. It is these pulses that are irregular. They can also last anywhere from 3 to 5 seconds from min humming - max humming - min humming. This could happen twice in a row, or it could go 30 secs before another. It sounds "powerful" and dangerous...That's the only way I can descibe it...When it "winds up" (from min-max humming) it feels like it is going to keep going until it blows up - yet the chassis is safe (at least I don't die if I touch it! ) and the sound dissappears.

I hope I haven't confuse people more! If I have, just go on my original post...or ask and I'll try to explain it again...
Gaz

Hi Rarkov,
To me it sounds likes remote commanding pulses from the powercompany to set the switch in your fusebox to "day" or "Night" electricity. Nighttime is cheaper. Sometimes these sounds come trough in most peculiar ways.

 

[Elso Kwak]

Re: DC - block / filter

Something like this? (Pic).

Arne K

Hi Arne,
C2 and C3 in the line filter should be X-rated for electrical safety (not for juvenile!)
See also :
http://db.audioasylum.com/cgi/m.pl?forum=tweaks&n=30901&highlight=elso+risch&r=&session=
Hope this helps,

 

[wuffwaff]

I build the circuit without C2/3 and the chokes and it works just fine. Even the two caps are a bit too much. Just one is OK.

See the attached picture of the LC-Audio DC-Filter.

william

 

[Nelson Pass]

Would not using Schottky didoes help?

No, you want the voltage drop of the diodes to be
greater than the DC, in fact we find that we are having to
series two diodes to get the required drop these days,
as the problem seems to be getting more severe. You
can use a nice power rectifier bridge for that.

 

[Rarkov]

Philo:
No the sound does not die when touching the chassis.

Elso Kwak:
Not sure if the power changing theory is correct - I know it happens, but this is every 30 secs or so, not evenings only.

wuffwaff:
Very interested in this seemingly simple circuit. What is the red component there? Can you post a scheme? Is that to just the live wire, not the neutral aswell?

Nelson Pass:
I have a space for an extra BR. I just had a go at working out what you meant by using a BR to give the equiv of two diodes in series. All I can get is two sets in series, but both pointing thew same direction, and they need to anti-parallel, not parallel. Have I missed something?

Thanks for everyone's help...It seems like a few people have had this problem. I don't think I've got the space to put everything into the monoblocks, so I might make a seperate mains distrubution block incorperating it all.

Thanks,
Gaz

 

[peranders]

The attached schematics earlier covers the problem except for the optional filter.

One thing though: Why are they using DC-blocking on BOTH wires?? I believe that one is sufficient.

Also the transil? I would choose a VDR.

 

[peranders]

I just had a go at working out what you meant by using a BR to give the equiv of two diodes in series. All I can get is two sets in series, but both pointing thew same direction, and they need to anti-parallel, not parallel. Have I missed something?

The diodes, check the attached schematics once more! The diodes are for voltage limitation (max +-1 Volts across the cap) and for inrush currents.

 

[saurus]

Here is the previous thread on this subject mentioned earlier by mlloyd1:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=2080&highlight=mains+filter+hum

 

[peranders]

Re: Me too

I also have a buzz from my Plitron 400VA toroidal, but my hum is very regular and even. It isn't always present, but it doesn't seem to correspond to turn-on, or warm-up, or anything else I can recognize. Seems to fade in and fade out over hours. Do you think this is also a DC-in-the-mains problem? I have a 100 R/100 nF across the mains before the transformer. I can live with it, if it isn't damaging the transformer (?). Thanks for the help!

I had the exact problem and a DC-trap helped.

 

[jarek]

buzz

Hi Rarkov,
If you disconnect all from the secondary of the transformer a 'hum' is still there?.
As I understand well you did two monoblocks than you should have two the same transformers. Is the buzz from both?
I know you did same amps and if it had been a dc problem it would have been the same with others. (IMO)

 

[lawbadman]

Reffering to the circuit Cobra2 posted, what kind of ripple current should I look for when I go buy a capacitor for the circuit?
And a 3 amp diode should be fine, right?

How about the 22000uf 25volt here: http://dkc3.digikey.com/PDF/T032/0668.pdf

 

[saurus]

I use caps with a max ripple current that just exceeds my mains fuse current (Panasonic TSUP series, 22000 uF, 25V, 6.1A rc, DigiKey # P6895-ND, US$6.26). Also used 5404 3A diodes. Works perfectly, completely eliminated the hum.

 

[lawbadman]

Thanks for the info saurus.

This circuit should handle the inrush current of my 3KVA transformer (two 1.5 KVA transformers) right?
Or should I build a second circuit for the other transformer?

 

[lawbadman]

can anyone out there answer my question???????????????????????

 

[dilbarzani]

Hi Peranders,
I've no idea about caps with doides. I don't even know hot use this thing. I'm having the the same problem. My newly bought Parasound Halo A21 makes humming. Can I buy that thing from some where that you are talking about here in this forum.
Please let me help me out this bcoz I'm getting nuts with this apm transformer hummmmmmmmming.
Thanks and best regards

 

[TonyTecson]

I have two large monobloc tube amps...the power supply transformer on one of them is emitting a 60 Hz hum..real annoying at low levels..any suggestions. I don't think it's dc on the mains because..as I said...only one amp does it.

thanx
rt

are you using steel chassis? EI traffos? i asked because in one monoblock i saw, it was the bottom plate vibrating causing humming, so my fix was to put a 6mm plexiglass in between the bottom plate and the chassis, holes were cut to allow the normal ventilation....

if using an EI traffo, you can try tightening the bolts, if that does not cure the humming, then you have to dismantle the traffo, wedge the core and the winding and dip in insulating varnish....