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Finally got around to adding an aux input to my factory radio. I tried the Bluetooth board I bought, but kept having ground noise issues, so I just used an aux cable instead.
I soldered the left and right wires of the aux cable to the L and R #2 inputs(AM Radio) on the preamp chip and ground to ground. This way I still get to use the chips equalizer and balance settings. I desoldered the AM tuner connections so that I won't get any buzzing. So now if I want AUX, I set the radio to AM. FM Radio still works great.
Here's some pics and the data sheet of the chip in my radio. Note - The left and right are shown here as being soldered to the #3 inputs. I switched these later to the #2 inputs, overriding the AM signal.
My phone puts out too much voltage, so I'll have to add a 100k trimmer pot so I can tone it down, but my battery powered 3.5mm Bluetooth receiver works great.
1992 factory radio with added Bluetooth round 2.
I added a step down voltage converter and an isolated 12-5v converter.
This got rid of the ground loop noise.
They, um, what's the word.....
I don't have a write-up on it. Every application will be different so it would be hard to make a catch all write-up.
I believe the part number for the '85 trucks is 19A241. I haven't opened one of these, and so I am not sure if they have a pre-amp chip like the newer ones have. They are likely not digital at all.
That is just like the one I pulled out of mine in 2001 aside from I think the knobs were different and mine wasn't a premium originally (so no fade with only the two dash speakers) I was thinking of the later ones with the equalizer for this adventure.I believe the part number for the '85 trucks is 19A241. I haven't opened one of these, and so I am not sure if they have a pre-amp chip like the newer ones have. They are likely not digital at all.
The later trucks(86/88 and later?) used 19B131 and 19B132, which do have the pre-amp chip.
Here's one:
Ebay Link
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