Problem with LM1036 amplifier

[Johan Alexandersson]

Okay, so we're doing an electronics project in school. Bear in mind that I'm not that experienced in this field. Anyway, we've built an amplifier circuit which contains, among other things, an LM1036 amplifier. We're having some problems with this component.

On page 7 of the datasheet found here https://www.ti.com/lit/ds/symlink/lm1036.pdf you can see how this component is applied. We've used pretty much the exact component for resistors, caps and such.

Now here's the problem. If we send a sine wave to input 1, we get a corresponding sine wave on output 1 but with increased amplitude. Pretty much what we want. However if we send a sine wave to input two, we somehow get a DC voltage at output two. The DC voltage we get is the same as the supply voltage we're using, so it might be related to that somehow. However, we don't know why we get this, and as you understand it is quite troublesome, as we need to use both inputs.

Any ideas of how we might have screwed up this circuit?

 

[FvM]

Obviously both channels should behave identical.

Simple explanation: Either your external circuit has an error (e.g. electrolytic capacitor with flipped polarity) or the device is defective. Measuring the DC level at all pins might help to narrow down the problem.

 

[Audioguru]

The LM1036 IC is not an amplifier, instead it is a tone controls circuit. It can boost or cut high and low audio frequencies and also has a volume control and a balance control.

 

[KlausST]

Hi,

Output2 must not have DC voltage, because it is AC coupled with the capacitor.
The voltage on the othercleg of the capacitor may have DC, but i' d expect it at half of supply voltage ( but it surely depend on the ICs inner circuit).
If the IC's output is very near to the supply voltage, then it may be externally connected (accidently by solder), the gnd pin is not correctely soldered (then the other output should not work also), or the IC is fried, or the corresponding input is DC also.

Hope this helps
Klaus