I just finished getting bluetooth audio working on my 84' Aspencade. Here are some pics and the description.
- removed the RM-1100 cassette/radio
- removed the front faceplate, top cover and bottom cover from the radio
- disconnected three cable connectors from the Tape EQ & Ambience circuit board
- removed two screws holding the circuit board
- slide the circuit board out the bottom
- unsoldered the left leads (coming from pins 8 and 9 IC 502) of the two capacitors (left and right audio) circled in red in the images
- soldered wires to the now disconnected leads of the capacitors
- soldered wire to the Accessory +12v pad circled green
- soldered wire to the Ground pad circled blue
- soldered a 1/4" headphone cable to the audio wires
- soldered the +12v and ground wires to a 7805 voltage regulator input
- soldered a mini-USB jack to the 7805 output
- disassembled a $7 bluetooth audio receiver (http://r.ebay.com/MijoDB
- taped the bluetooth receiver to a piece of cardboard so it would be thin enough to fit into the cassette opening
- reassembled everything, with the mini USB and headphone cable coming out the cassette opening
- tested - it works! Pushing the volume knob to switch to the tape input causes the radio to turn off, and the bluetooth audio sounds great. Unfortunately, if the radio is selected, the bluetooth audio is mixed with it. No big deal.
- pushed the wires and bluetooth module into the cassette opening.
Looks 100% factory, but now I can listen to bluetooth audio.