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Mains hum problem

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yash gupta

New Member
Thankyou very much for your help Hero.
The noise has already got low many times by using shielded cables and putting a sheet of foil, insulated by cardboard under the pcb.
The next time I make a pcb, I will surely consider your advices.:)
 

mvs sarma

Well-Known Member
thanks.

Here's my pcb art work
**broken link removed**
Mr Gupta,
please put 0.01uF disc capacitors, one across each diode in the bridge rectifier circuit and the hum would disappear. All the best.
 
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aljamri

Member
and putting a sheet of foil, insulated by cardboard under the pcb.

In my case I'm using aluminum foil connected to my ground, and paper sticker to fix it in the floor of my box where I put my circuit. it is doing fine.
 

mvs sarma

Well-Known Member
once power supply is conditioned with the caps i suggested
no need perhaps for all those shielding
 

aljamri

Member
once power supply is conditioned with the caps i suggested
no need perhaps for all those shielding

Looks great, if I have time I'll try on my poor circuits. By the way, is that 103 or 104 caps ?

Thanks
 

Hero999

Banned
Thankyou very much for your help Hero.
The noise has already got low many times by using shielded cables and putting a sheet of foil, insulated by cardboard under the pcb.
The next time I make a pcb, I will surely consider your advices.:)
Yes, that will work.

The foil should also be connected to 0V, for optimum shielding.
 

yash gupta

New Member
yes, I forgot to mention, I have grounded the foil as well. Thanks.
 

yash gupta

New Member
Mr Gupta,
please put 0.01uF disc capacitors, one across each diode in the bridge rectifier circuit and the hum would disappear. All the best.
Thanks. I also have seen the caps put across the rectifier in the supply os a cd player I ripped apart.
Please tell me how does it work? Doesn't the ac signal get into the dc supply through the caps?
Please explain me, just for knowledge.
 
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