K4003

Having assembled the kit I am getting a loud hum on both channels -without any input connected

I have tried using shielded wires for both input and output leads but it makes no difference

The transmformer is 2 x 12VAC but only rated at 12VA - I realise this is low but would it cause the problem?

I have now read other posts and note that the mica insulator is probably w s not installed correctly - corrected.

I have checked IC pins with voltmeter set to 20 V DC - no input signals present

Pin 1 0.8v Pin 2 3.88v Pin 3 0v Pin 4 -3.69v Pin 5 -5.6v Pin 6 1.55v Pin 7 4.8v Pin 8 0v Pin 9 0.5v

Does it appear that I have damaged the IC and if so would it be the low rated power supply that would have done this.

Advice gratefully received.
Mike

Thanks

12VA is too low. You need 50VA. Short both audio inputs on the board. If hum dissapears, unit is working fine.

Thanks - new transmformer on order - expected tomorrow - will try as you suggest.

Mike