TDA2030 Hum

[prezden]

I have just completed a 2030A kit from ebay. When I hooked it up to the power supply (2x9V) all I get is a hum. No music just a hum. I have tried connecting it in both series and parallel and to a different transformer with same result. I've looked carefully at the board but can't see any obvious problems.
Any advice would be greatly appreciated. I had planned on replacing all the caps systematically to do some listening tests as I go along. But now I'm not sure this thing is worth the cost of the new components.

 

[Arty]

short the input. -> is the hum still there?
make sure to check all solder points again, reheat if You are uncertain. -> is the humm still there?

If the input is "floating" -i.e. not connected to anything- it acts like an antenna picking up junk only.
Mostly its not humm, but it CAN be.

 

[Jay]

Start wiring properly. Shielded cable for input signal etc.

 

[Robert Kesh]

what the hell has happened to the third from left green electrolytic?

 

[prezden]

That one was damaged when the package came from China. This kit was supposed to have Chemicon and Panasonic capacitors but all it had was cheep Chinese crap. I had planned on replacing the caps when I get it up and running.
I just tried running it with a 12v wall wart - no hum but no sound either. This evening I am going re re-wire the inputs with some proper wire.

 

[prezden]

Thanks for all your suggestions-
I rewired the power mains and input wires. Also checked all the soldering and touched up a couple spots. Still no music - just hum

 

[Robert Kesh]

change that cap then

 

[Minion]

well , it looks like there might be a resistor missing and you don't have the dual potentiometer connected , without the pot connected it wont pass signal ......

 

[prezden]

The missing resistor is now supposed to be used in the OCL circuit. I was wondering about the pot. I didn't want to use the on board one so haven't wired up the one I will be using. I was hoping to get the problem of the hum resolved first.
Could the damaged cap cause the hum?

 

[Minion]

without the pot the input signal is left floating and unconnected which will cause it to hum ....... connect the pot and the hum should go away , if you don't want to use a pot short the second and third pins together on each row ......

 

[johnr66]

Where does the green wire go on the supply in? I see only two wires off the transformer's secondary. Unless it is out of the picture, the green wire must be connected to the center tap on the transformer's secondary.

use a 40 watt bulb tester when setting this thing up.

 

[prezden]

I connected the on board pot and inputs. Still humming away with no sound (music) This is most confusing

 

[Robert Kesh]

Could the damaged cap cause the hum?

yes. it is possibly shorting out whatever is connected to it.

 

[prezden]

Part 2: I replaced all the caps and have had 50% success. One channel is working quite well. There is a very slight hum. The other channel has no audio and a loud hum. I have narrowed the problem down somewhat. By removing one of the caps (C8) the hum is gone but there is no audio. I have tried 2 caps at this location with the same result.
I'm stumped

 

[prezden]

Hello again- I replaced the c8 it still hums. By bridging between c8 and the output gnd the hum completely stops but there is still no audio. It's a shame because the other side sounds pretty decent.
Any ideas?

 

[Jay]

Looks like a bridge amp PCB??