TDA 7386 Help Please

[supersonik]

I built a TDA 7386 circuit using the test circuit in the datasheet, with only two changes. I tied the MUTE and STANDBY pins directly into Vs (no RC circuit) and I only use 2 of the 4 inputs. I cannot get sound from any of the outputs. When I put my multimeter in line with the power supply to measure current, it reads as 50 mA for a few seconds, then jumps up to ~150-300mA. Can anyone help me? The datasheet said that a straight connection to Vs of the MUTE and STANDBY pins is admissible, and I don't see how unused inputs can be a problem.

[pacificblue]

Although it says in the Stand-by and Muting section "R-C cells have always to be used" it should work without them. The current consumption looks to be in the correct range. 50 mA until the capacitor at the SVR pin is charged and then a quiescent current in the specified range. Are you sure the speakers are connected to the right pins?

Do you get a voltage at the HSD pin that indicates a fault?

Can you disconnect the mute and stand-by pins and connect them a few seconds after powering up the amp? Just to make sure those pins are not waiting for a rising flank.

[supersonik]

Which pin is the HSD pin? I'll try to disconnect the mute and standby pins in a few minutes.

[pacificblue]

Oh, the HSD pin is not connected internally. Since it is shown in the datasheet on pages 2 and 4, I assumed it had the same functionality as in the TDA7560. That means DC at the output would go undetected.

In that case, you should re-check all connections for continuity and correctness, that the supply voltage is present at all relevant pins and redo all solder joints. Capacitor polarity could be an issue, at least for the capacitor at the SVR pin (10).

Can you post photos, where all connections are visible?

[Redshift187]

Don't you need at least the resistor on the MUTE and STBY pins for current limiting?

[supersonik]

Oh my god I finally got it working. As it turns out, signal ground does not mean connect it only to the ground of the signal, but to the ground of the power supply too. Woooooooow that took me three whole days to figure out. Anyway, I found the answer by accident by brushing against the wrong part of the circuit board with an alligator clip. Accidents can help out.