Help Sony AU BUS for SDP-D905

[relax79]

Hello friends, sorry for m poor English, I have a sony sdp-d905 signal processor, this is part for lbt-d905 stereo systems. It works only digital input, I am must turn to input analog but only works with using ta-d905 amplifier and connecting au bus cable. Amplifier decides processors input,  I have not an amplifier and I must activate the analog input. In service manual au bus looks like one wire protocol and I have bus pirate for connecting to au bus but I do not know what commands needs for this. Anyone familiar or observe this protocol with logic analyzer or do it for me if have this system in the hand. Thanks

[Electric Canary]

Hey!
I know this is a very old post but I had the exact same problem and here's how I managed to get the analog input/output back. This is a crude method and it deactivates the digital inputs and the AU bus. However I'm not too sad about that since RCA seems to be way more popular and I don't have the whole LBT-D905 system.

IC501 is responsable for the input selection and the mute switching.
Basically you need to ground pin 25 and 32 to unmute the analog path. Then you have to put 5v to pin 29 (it selects between analog and digital input). To do that I unsoldered pins 32 to 25 of IC501. You can probably get away with unsoldering just pin 29 and grounding the rest of them. You will find 5v at pin 33 to connect to pin 29.

Once your signal path is set, I measured a -2dB difference at the output. You can compensate that by grounding pin 58, it activates a 2dB boost at the output.

I found this method by checking the repair manual again and again. Not sure if there's any flaws other than deactivating digital inputs and au bus.

[Gavinda]

First i need to thanks for your method sharing.
I also has same problem & while i searching for solution i found your method.
Could you please help me how to select 2 other digital inputs ??

[tooki]

FYI, electrically, the AU BUS is the same as the later Control A system for audio gear, which is electrically the same as the Control A1 system, which was later extended to Control A1 (II), as well as Control S (for AV gear) and Control L (also known as LANC with various connectors, for camcorders). They’re also all often combined under the “S-Link” umbrella, so you’ll often see the terms used kinda interchangeably. Regardless, it’s all a 5V open-collector bus. You can find the pinouts in service manuals, but you can also just turn it on and measure the voltage: when you’re showing +5V, your positive probe is on the data line and negative is on ground.

The differences are in the signal format, but all are apparently variants of SIRC, Sony’s IR remote control format, and some service manuals even refer to the Control A bus as SIRC. There are various Arduino projects out there to control this, mostly for A1(II) and LANC.

As I understand it:

Control-S is simply standard Sony IR commands, without the 40kHz IR carrier frequency. See http://www.armory.com/~spcecdt/remote/control-S.html
http://boehmel.de/sircs.htm

I have a strong suspicion that AU BUS and Control A are exactly the same thing as Control-S, and that all of them except Control-L are fundamentally little more than different versions of SIRC (which exists in 12, 15, and 20 bit versions).

Control-L/LANC omits the device address, since it’s only ever used for 1:1 connections, and apparently is shifted by one bit:
http://boehmel.de/lanc.htm

AU BUS seems to have been used for a long time, always between devices in integrated systems.

Control A seems to be quite rare, found only on a few devices before Control A1 came along around 1995 or 96.

Control A1 appears to be a major departure from Control A, with only limited interoperability:
https://www.minidisc.wiki/_media/resources/sony_s-link_control_a1_control_system.pdf

Control A1 (II) extends A1 to allow bidirectional communication, but remains essentially compatible with A1:
http://boehmel.de/slink.htm


This project page has a bunch of links to info on the protocol:
https://github.com/Ircama/Sony_SLink

There are various online repositories of IR codes, and that may include Sony codes suitable for the device in question.