Hi all,

I have a BC9300 in the bench. On PCB8, the preamp, the scope shows good AC audio input from all the opamps into the TDA7318, but there is no AC audio output on the Audio Signal Output pins 24 and 25 - just dead.

All voltages check, and if I bridge pins 6&7 and 16&17 (with a 2.2uF according to the datasheet), effectively bypassing some of the circuits, I get sound, but not via pins 24 and 25.

So I think the TDA7318 is faulty.

The real issue is whether these have been specially programmed by B&O (the datasheet mentions programmable, but I'm not sure of what exactly), or can I just buy a new one off the shelf?

Regards

Menahem

"Programmable" in this context only means that the functions of the chip are controlled via the I2C bus, so you can replace it, they are all the same.

On the other hand, the fault could be just as well that nobody controls this chip (problem in the CPU, or the I2C bus is stuck for some reason). At least confirm first with a scope that there's some traffic on the SCL and SDA lines before just attacking this chip, I can't think of any reason why it should be dead, being safely buried of out the reach of outside world...

Thanks Mika,

I've checked the signals on Pins 27 and 28 - a nice beep every second or so, so the control signals are there.

This machine was not in great shape when the customer delivered it, no sound, CD not working, etc, lots of rust on the underside.

I did a nice upgrade, all Elna and Nichicon Audio caps in the signal path, 11DQ10's and 31DQ10's on the PSU, new laser, calibration, etc.

I tapped the AC off the opamps before the preamp, and ran it into another preamp , to test - sounds good.

I'll order a new TDA7318 and see what happens, in the meantime, I've put in a DIP-28 socket to save extra work later.