Pioneer mini stereo - audio issue

[notallbad]

Everything appears to work as it should except for sound.
Theres no sound coming out of the speakers but can just vaguely hear sound through the headphones with the volume turned almost up to its maximum. Tested with cd in cd player, mp3 music file on usb stick, radio station tuned in - same result!

Headphone jack ok, hp-detect shorted with headphones unplugged and open cct when plugged in.

Meter shows short circuit between the l + r speaker outputs.

TAS5719 Digital audio power amplifier chip on mainboard.

Power supply board voltages all appear to be correct.

Would my assumption/checks so far indicate that the TAS5719 needs replacing?

[notallbad]

Re: Pioneer mini stereo - audio issue

As well as all speaker outputs shorted they are also shorted to gnd.

[notallbad]

Re: Pioneer mini stereo - audio issue

Voltages on TAS5719 appear reasonable , 3.3v and 22v etc and the internally generated 1.8v.

Removed the 4 inductors and the short between speaker outputs has gone.

Would seem that the TAS5719 has pins OUT-A , B, C & D shorted.
And BST_D and OUT_D has a low resistance reading of 7 ohms.

[momaka]

Re: Pioneer mini stereo - audio issue

Ah, it's one of those class-D ICs with digital inputs. In that case, it's hard to say what exactly is going on. It could be that the IC is working, but due to lack of or improper input signal clock(s), the outputs are placed in a low-impedance state to ground. But it could also be that the IC has shorted outputs and going into protection mode... in which case, perhaps it should be relying that data back through the I2C bus to indicate a fault... but then again, that may or may not be implemented with whatever IC the TAS5719 is connected with.

That said, from what I see in the datasheet on pages 20 and 21 for protections, pretty much any fault will place the H-bridge outputs for the speakers in a high-impedance state, meaning both upper and lower FETs in the H-bridge should be open... therefore, the short-circuit you see to ground does sound problematic. Of course, I'm assuming you did that resistance measurement with the power off (don't mean to undermine your troubleshooting skills in any way, but just want to verify my assumption is correct.)

Other than that, I can't really give you much useful help here. If the TAS57819 is readily available and cheap, probably may be worth to try and replace it to save some time on troubleshooting (unless you don't mind that and really want to find out what the problem is.) With all those digital inputs, I really don't see how one could go about correctly testing this.