I eventually managed to obtain a replacement CXD9788AR stream processor from Alltronic Computer Singapore. This has cured the fault. The volume control now operates correctly.

So, in summary:

Symptoms: The volume control varies the display from MIN, then 1 up to 30 and then MAX as expected. At MIN there is no sound. However, at 1 it is quite loud and increasing above 1 does not change the sound level.

Cause: Faulty CXD9788AR stream processor IC705.

I have made some further progress with the Sony HCD-HX80R. The volume control does not work the way that I had assumed. A functional description to go with the block-diagram in the service manual would have been nice.

In the block-diagram IC501 (BD3499FV) is labelled 'INPUT SELECTOR, ELECTRICAL VOLUME, SURROUND / TONE CONTROL'. The data sheet shows that it is capable of performing a volume control function in dB. However, it is not used to control the volume. The System Controller always sets it to either -infinity or -12dB. This is what is causing the volume to go from nothing to...

I have a strange fault on a Sony amplifier. The volume control varies the display from MIN, then 1 up to 30 and then MAX as expected. At MIN there is no sound. However, at 1 it is quite loud and increasing above 1 does not change the sound level.

I have tried a Cold Reset as per the service manual.

I have looked at the I2C clock and data to volume control chip IC501 (BD3499FV). Data is only sent to IC501 when the volume is set to MIN or 1. At any other setting no data is sent to IC501.

I have looked all the way through the service manual and tried many online...

Re: New Members - please post your introductions here

Hi all, I am Robert from Dorset in the UK. I found this forum while searching for help with repairing a Denon AVR-2802 amplifier. I have really gone down the rabbit hole with this repair. When you start reading about the boot sequence for a DSP chip, you know you are in trouble. Why are things so complicated these days?