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FS: Mains DC blocker.

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nigelwright7557

nigelwright7557

Member
Joined 2008
murtonpikesystems.co.uk
#1
Got a grumbling toroidal transformer ?

Sometimes this is caused by DC on the mains.

This unit blocks DC to the transformer.

Mains DC blocker up to 1500VA toroidal transformer with UK 230VAC mains.

Or up to 750VA toroidal transformer with 115VAC mains.

Simple live in/live out terminal block connections.
£4-99 each plus p+p (£3-99 UK,. £10.99 rest of world.)
An externally hosted image should be here but it was not working when we last tested it.
 
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#3
glennjarrett said:
Hi Nigel
Just what i am looking for mine buzz like a bloody fridge !
would you be able to upload pics please or give a bit more info size etc
I live in Accrington so UK postage

Glenn
Click to expand...

Its 60mm by 50mm, its quite small.
Just a connector, two caps and a bridge rectifier on a green pcb.
Make payment of £8-98 to paypal sniffntears@talktalk.net
If you make payment as a friend you will need to send me your address.
Regards Nigel
 
#4
How do these work exactly? I have a small amount of buzz through my speakers when no signal is fed and the volume is turned up. I assume it is from my toroid based psu.
I see a rectifier so doesn't your unit provide DC?
Sorry for the newbie question!
 
#5
jimk04 said:
How do these work exactly? I have a small amount of buzz through my speakers when no signal is fed and the volume is turned up. I assume it is from my toroid based psu.
I see a rectifier so doesn't your unit provide DC?
Sorry for the newbie question!
Click to expand...

They basically stop the toroidal transformer buzzing as they remove DC on the mains.
Hum in your system is something quite different.
 
#9
EI transformers more often hum because of mechanical properties as loose (so vibrating) laminations. AFAIK they are not so sensitive as toroids for mains pollution/DC component.

The more VA the more a EI will hum it seems. However with small EI transformers coating the core may make it less hum. Only works when it has a low load and stays relatively cool. Although empirical I used slow curing epoxy for that as it was meant to pot transformers. Potting them makes them really silent but who knows how much you can load them when potted?!
 
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#10
So basically using a DC blocker for my EI transformers shouldn't make much of a difference? Maybe I will try it anyway, just for the heck of it. I'd buy a board from you Nigel, if you still have them for sale? I could mount it in an external enclosure so I can test different equipment with it.

I might potting the transformer at a later stage too.
 
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