eliminating FM from source select

[whiterabbit]

I've been working on a project that controls Unilink devices without having an FM radio or Volume control, as the ultimate goal is to use the unilink devices as sources hooked up to an alternate preamp that is already in service.

Sony made a device for me in 1998 that does just this. Unfortunately I have two limitations. #1 no future expandability. Thus, no HD radio, no ipod, no USB connectivity, etc. Only CD changer control. Which admittedly is 80% of what I want. #2 They are very tough to find. I purchased three off ebay and all are in various states of disrepair. A buddy suggested the firmware may be defunct after a decade.

The potential solution to the problem is to use a late model Sony CD player. This solves a huge number of firmware problems and updates the control, too. The faceplate can be taken apart so only the LCD is exposed and all other electronics hidden. Volume control would dissappear.

This presents one HUGE problem though. Source Select will still cycle through the FM radio and the onboard CD player.

Is there a way I can cut traces on the main board, or other "simple" modification to the device such that those sources are eliminated from the source select cycle?

do I have alternate choices available to me to accomplish what I am trying to do?

Thanks guys,

Steve

[whiterabbit]

I'm adding more data as I've discovered; Some of the more PIC experienced can hopefully chime in with a better interpretation than I.

http://users.ntplx.net/~andrew/sony/unilink/

here is an excerpt:

"-There is no direct slave to slave communication. The master allows all communication. (the slave can request that the master talk to them)
-The basic head unit is the master. It's tuner, keypad, display, cd unit, and tape are all 'internal' slaves. The master is just a CPU in the head. This allows all units internal and extrnal to be 'equal' "

The slaves of interest of course are the CD unit and the tuner.

more:

"Inital Link
The master must find all slaves:
Each slave will be polled with the Anyone command short word
The slave responds by telling the master what group type it is.
The master will assign the slave a member address in its group
The slave will remember the address and acknowledge its new address
The master ends polling with Appoint end command short word
The slave returns a NAK to end the link
The master will then issue the Link On command to see if there are more slaves beyond the one it just found. "

So it seems to me this is what I want to interrupt. If I can cut the polling line to the tuner and the cd player (or bypass it if it is a 'token ring' physical configuration for communication), then both sources can wave their arms and say "look at me!" all they want, and the master will skip right over them when I hit "reset". This would make my job much easier...

Is this the same interpretation other folks here reach?