Hum with Arduino Radio with a TDA2003 amp

Other Hardware General Electronics
1

Hi,

I've made a digital radio tuner with a TEA5767 FM receiver and TDA2003 amplifier. For some reason it generates a slight hum which I've not be able to remove. Does anyone have any ideas how to solve. I'm gonna try a big filtering cap tonight. I've attached the schmatics and a pic of my breadboard. When I used a LM380 there was no hum.
Thanks

Mase

Design.png
Design.png2557×1657 43 KB

Breadboard (Large).png
Breadboard (Large).png1440×1080 496 KB

2

Transformer needs to be well away from the signal wiring - is this the problem?
Grounding is done sensibly?

You seem to lack decoupling on the ATmega328 BTW.

3

Do you have 10 nF over the rectifier diodes?
It may help.

Pelle

4

Hi, another 1000uF will help, but as said by most replies, layout is critical.

Tom...... :slight_smile:

5

Thanks Mark, you're right i took that out because I thought I didn't need it because of the 470uF cap I have, but that's my lack of electrical science :frowning: I will put it in. Currently the 3 ground signals from the amplifier circuit go straight to the ground on the rectifier. The transformer is on the other side of the table so it can't be that.

MarkT:
Transformer needs to be well away from the signal wiring - is this the problem?
Grounding is done sensibly?

You seem to lack decoupling on the ATmega328 BTW.

I've also seen this on a schematic yesterday, I'm gonna also give that a try too! Thanks Pelle :slight_smile:

Pelleplutt:
Do you have 10 nF over the rectifier diodes?
It may help.

Pelle

I've added a monster 2200uF to the input from the rectifier but that didn't help.

Thanks Tom

TomGeorge:
Hi, another 1000uF will help, but as said by most replies, layout is critical.

Tom...... :slight_smile:

6

supercrab:
Currently the 3 ground signals from the amplifier circuit go straight to the ground on the rectifier.

Try to connect both + and - directly to the capacitor.
The current from the rectifier to the cap are NOT so nice. With some resistans i will be some mVolts.

Pelle

7

Thanks Pelle! I shall give that a try! I need to move my big cap to where you suggested. It's currently in the wrong place :roll_eyes:

Pelleplutt:

supercrab:
Currently the 3 ground signals from the amplifier circuit go straight to the ground on the rectifier.

Try to connect both + and - directly to the capacitor.
The current from the rectifier to the cap are NOT so nice. With some resistans i will be some mVolts.

Pelle