# Adding Bluetooth to stock 94 f150 radio



## ayriggins (8 mo ago)

I have a 1994 Ford F150 with a stock radio that includes a tape player that I'm currently modifying with a Bluetooth receiver. My plan is to splice into the tape deck. I was able to get power to the Bluetooth receiver, but I'm struggling to get sound out of it. I removed all of the springs for the tape deck so that it always thinks there is a tape in the deck. The receiver has the red and white rca outputs, which I cut off to expose the wires. In each there is a white and red wire. I only used the white wire for both. I spliced them into wires that go into a harness for the tape deck that is labeled TAPIN, and also shows an L and a R for the red and white wires. My guess is that I'm not spliced into the correct wires for the sound. I'm including pictures that will hopefully give a clear picture.


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## daloudin (Nov 2, 2020)

I would expect that both white wires from the BT Receiver RCAs should be connected to the "Common" connection for the TapeIn and then each Red wire from the RCAs would go to the TapeIn L & R.


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## ayriggins (8 mo ago)

daloudin said:


> I would expect that both white wires from the BT Receiver RCAs should be connected to the "Common" connection for the TapeIn and then each Red wire from the RCAs would go to the TapeIn L & R.


So I tried that with no luck. I currently have both white wires spliced into the common, and then I have the red wire from the white rca connector spliced into the left channel, and then the red wire from the red rca connector plugged into the pink/red wire of the right channel. I did try it reversed and that didn't seem to work either. The attached photo shows the splices, which I am aware looks rough but these wires are so thin I'm trying to be careful with them until I get it right.


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## daloudin (Nov 2, 2020)

Not to be antagonistic but are you sure that there's signal on the wires and that the HU is on Tape function?

If you turn the volume up on the HU and touch the wires with your finger (not shorting the wires just touching them) you should get some crackling noise from the surface charge on your skin.


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## ayriggins (8 mo ago)

I'm very far from being an expert, so nothing could be antagonistic. 

I can confirm the head unit is on tape mode. It shows tape on the screen and it's spinning like there is a tape in the drive. Touching the wires on the TAPE IN did not cause any noise changes though. I do have the volume turned to the max as well.


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## daloudin (Nov 2, 2020)

Without an oscilloscope and confirming Transistor Voltages and signal path, I'm not going to be able to help much. I "think" you're doing it right but I'd also think that you should get some noise on those inputs if they are active...


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## Hintzyboy (Mar 31, 2007)

Just to throw it out there, why exactly are you going through the trouble of doing this for a 1994 F150? I love to tinker with **** like this as much as the next guy, but it seems you'd get a lot more functionality for not a lot of money by just getting an aftermarket HU. It's not like the car is some valuable classic where preserving the stock look is a big deal.


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## knever3 (Mar 9, 2009)

Hit up Minuit on Comanche Club, he's a wiz at modifying old radios, yeah he's a Jeep enthusiast, but a radio's a radio.






What Minuit knows about stock Jeep radios


What Minuit Knows About Stock Jeep Radios Got a question? Need one of these radios repaired, or want to buy one? Check out my website! What is this? Simply put, it's a compilation of my findings regarding the factory radios installed in Jeeps 84-96 with a focus towards those that can be installed...




comancheclub.com


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## Dark Winter (9 mo ago)

Umm... yeah... as much as I like the whole idea of "I made it myself"... this is one that I wouldn't do. I'd just get a head unit with bluetooth and USB inputs. Basic ones (even from reputable brands) are really cheap now.


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## knever3 (Mar 9, 2009)

I find these projects to be the most rewarding, Bluetooth is such an inexpensive DIY project. I have considered this on my 06 Grand Cherokee because I like the function of the radio and the looks. If it costs me $20-$50 to put a Bluetooth module with power supply in the radio with a soldering iron it's worth it. Some projects people won't understand the DIY aspect of it. Sure a new radio would be easy, but it might not be what you are looking for. Let us know how you progress.


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## Hintzyboy (Mar 31, 2007)

Like I said before, I like to tinker with this kind of thing, too. But saving money isn't really a great justification. Your time is worth something. If I had to spend more than an hour or two messing with it, then I'm better off buying an aftermarket HU. 

If saving money isn't really the goal, then that's a different story. I've done plenty of things just to see if I could do them. Just depends on how you value your time and where your priorities lie.


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## ayriggins (8 mo ago)

Saving money isn't the goal, and the tinkering is a big part of it. I do like the way the head unit looks in the dash, and I'm trying to keep the truck as "stock" as I can. 

I actually was able to get sound. When I was removing springs to make the HU always think there was a tape, I took out one too many so the tape deck wasn't engaging properly. The last part I need to figure out is where the black wire goes from the power of the receiver. I figured this was a ground wire, and hooked it to a screw. This completely kills the sound. When it's hooked to nothing, the sound has a ton of static. I'm including another photo of the wire harness that goes into the TAPEPWR. The Bluetooth receiver came with a red and black wire for the power. I matched the red wire with the red wire on the harness, but since all the rest of the wires on the harness are white, I'm not sure where to hook that one up without losing the sound.


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## khlae (Dec 31, 2016)

Its not the easiest to tell, but looks like you've combined the old signal with your new aux signal instead of disconnecting the old signal source? You don't wanna combine them like that, it could make it act weird/not work.

Looking at daloudin's PDF, I think you've tapped the input to the tape preamp, and that goes to the ic851 chip. You might have better luck disconnecting ic601 audio output pins and injecting your bluetooth directly into ic851 tape input pins? It would be good to check input/output impedance and voltage levels those chips expect.


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## khlae (Dec 31, 2016)

edit: pushed the wrong button and didn't look closely enough double post.


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## ayriggins (8 mo ago)

khlae said:


> Its not the easiest to tell, but looks like you've combined the old signal with your new aux signal instead of disconnecting the old signal source? You don't wanna combine them like that, it could make it act weird/not work.
> 
> Looking at daloudin's PDF, I think you've tapped the input to the tape preamp, and that goes to the ic851 chip. You might have better luck disconnecting ic601 audio output pins and injecting your bluetooth directly into ic851 tape input pins? It would be good to check input/output impedance and voltage levels those chips expect.


I'd love to bypass the TAPE player, but how would the radio switch to tape mode without it? I'm also not sure how to tap directly into the IC851


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## khlae (Dec 31, 2016)

What I mean is, look at page 3 of said PDF, ic851 has two pins, tape-l and tape-r. What you do is desolder/cut/break the connections going to that chip and run your left and right single ended signals into those two points. given ic851 has separate am/fm/tape input pins and drives the amplifier ICs, that's the chip that switches between those three inputs. Cutting the traces on the circuit board and scraping the resist off so you can solder to the exposed trace is easiest but most destructive way to tap it. I think. I haven't seen the other side of the board.


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## ayriggins (8 mo ago)

khlae said:


> What I mean is, look at page 3 of said PDF, ic851 has two pins, tape-l and tape-r. What you do is desolder/cut/break the connections going to that chip and run your left and right single ended signals into those two points. given ic851 has separate am/fm/tape input pins and drives the amplifier ICs, that's the chip that switches between those three inputs. Cutting the traces on the circuit board and scraping the resist off so you can solder to the exposed trace is easiest but most destructive way to tap it. I think. I haven't seen the other side of the board.


I am attaching photos of the back of the board. Any help of where to solder the wires in would be great. Are the wires you are referring to the wires for the audio or the power? Sorry for all the questions, I have very little experience with this.


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## khlae (Dec 31, 2016)

In your picture that clearly shows ic851, on the left side there are the numbers 1 and 28 screened onto the board. Those are the pin numbers that correspond to the numbers in the PDF.

tape-r = pin 10
tape-l = pin 14
ground = pin 3 (did I miss any other ground pins?, a datasheet for the st70029sb chip would be useful to confirm)

The audio pins are going into the nearby c853 and c857, which you may or may not be able to bypass without problems. the trace going from c853 to ic851 is on the bottom, and the c857 trace is on the top.

It would be least destructive to desolder those capacitors and tap your signal there, either by putting your signal into the legs of the capacitors that face ic601(should be the legs marked with the +, you should be able to test for continuity to verify) or bypass the capacitors entirely. I've never touched this particular radio, so no warranties on this info.

(for other people looking at these images, the default image link is a resized webp image, swapping out image/format=auto, for image/format=jpg, you get the higher resolution source jpeg)


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