Synopsis
This page will summarize the quick and dirty mod of adding an aux cord to the Becker 612 Radio. This radio is from a 1984 W126 Mercedes but that isn’t terribly relevent. I suspect though this mod can be done to many other becker radios if you are a little clever about it.
Disassembly Process
I will assume the radio has been removed already from the car but you will see 3 metal bent flaps that need to pull away from the chassis. Once this is done the two large panels can be pulled away from the radio. Otherwise reference this guide which is pretty informative. We are specifcally interest in the top of the radio which has the ic that we want to insert our signal.
Mod Summary
Basically after searching throughout peachparts forums and other car forums I found a couple rough guides on adding aux. Most involved using some features of the tape deck (not terribly useful if your tape deck is broken) but the last post I found talked about just inserting your line level signal (3.5mm aux signal typically is this) directly to the output of a stereo decoder chip. In the guide for becker 1432 radio this IC is a TCA 4511. For the Becker 612 this IC is a TCA4500. Basically just solder your aux aux cord to the pins 4,5,8 (L,R,G) and you should be good to go.
Current Issues
- There is a loud poping noise that occurs when switching sources (pretty typical of sound stuff) but I am unsure of how to fix it.
- The cord just comes out through the cassette so not terribly clean but this can be routed differently.
- The point where soldered may not be ideal in terms of filtering and stuff. Should be checked later especially if schematic is obtained somewhere