mp3 jack mod for Sapphire radio - attractive and reversible!

[kentosh]

I have a '70 Bug, and the radio hadn't worked in ages, so I finally got around to fixing it (volume pot needed to be replaced) but I decided it was silly to put all this effort into an AM radio, so I wanted to make it mp3 compatible, and I wanted to make it look good, but most importantly, I wanted it to ENTIRELY reversible. I'm very big on keeping my car as stock as possible and refused to cut anything. I was very pleased with the results and decided I'd share with the world.

The radio I modified was a Sapphire XI. Before:

After:

Basically I removed the AM tuner knob and replaced it with a 1/8" phono jack and then I wired that into the circuit and disabled the radio. I took some ideas from this guy: http://homepage.mac.com/stokester/.Public/Sapphire_Hacking.pdf but I did it a bit differently. My modded circuit looks like this:

I ditched the switch because there was nowhere for me to put it while keeping this project reversible. I added a capacitive couple as a safety to make sure that the radio doesn't try to send any kind of DC current into my mp3 player. Anything over .047uF should be fine, I used .1. If it's too small you'll lose the low frequencies, but if it's too large it doesn't do a very good job as a safety device. I also desoldered the wire that went to the volume pot to silence the radio.

Ok so the first step is of course to get the radio open, but after that you need to get the tuner knob out. The guts of the knob connection should look like this:

We have to get that stuff out of there, but we have to do it in a way where we can put it back if we wanted to. The easiest way I found to get it out is at the universal joint. Both sides attach to a cross-shaped piece of metal, and it's fairly easy to pry one side off the cross to separate the unit into two pieces which should come out fairly easily. Afterwards it should look something like this: (don't worry about removing the rest of the AM innards - we only need space for the jack.)

Now is also the time to get the tuner position indicator thing on the front to an aesthetically pleasing location, because we're losing the knob. I found right after the 7 was perfect on mine.

Then I wired the 2 resistors and capacitor to the switch and inserted the unit. I did it point-to-point and it all kinda floats there, but it works. I also wired a specific ground wire and soldered that to a ground tab where something else was already grounded too, just to be sure i got a proper ground because I didn't trust the switch-case contact. The jack looked like this:

Then the volume pot side of it: First I found which side of the potentiometer shorted to the middle lead when the volume was on full - this is the lead I had to change. It also happened to be the one on top, easiest to access. I removed the wire which was attached to it (white), wrapped the end in electrical tape, and tucked it somewhere harmless. It's still in there in case I want to revert back to how the radio was. I then hooked up the wire from the new input circuit where the old one was. I only had red wire on hand, so I now have two red wires next to each other which serve different purposes, but oh well

Now it's time to test it. I hooked it up to a battery charger, a random 8 ohm speaker I had sitting around, and then my computer, and then turned on A Hard Day's Night, and it played! As you can see, I did all this on a kitchen table - there's no need for any kind of fancy shop, just a soldering iron, and a multimeter is recommended.

Now, the next part is the part I found most difficult - finding a washer to make the jack fit properly. Mostly because I installed the jack before I realized I needed a washer to make the thing fit securely (the nut was too small for the hole). I managed to find one at the hardware store for 5 cents, and here was the result:

All that was left now was to get the radio back in the car:

And now I have a Sapphire XI with a line-in, which I can convert back to stock configuration at any time. True, I lost the AM functionality, but who actually listens to AM radio?

I also tried plugging my electric guitar into the radio, and it works as a guitar amplifier as well! Not a very good one, all things considered, but how many people can say they have a guitar amp in their car radio?

[Lord Helmet]

Pretty cool idea.

EDIT: You could probably use an old mini jack and attach it to an original knob to hide it when not in use.
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[OldsCool]

[83_WabbitGTI]

Awesome write up! Thank you!
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[Hugo Stiglitz]

That is killer! Im all about keeping my dash stock! I was going to put an updated head unit with an ipod cable in the glove box, but now I might try this on an older sapphire instead. Great thinking!

[Buck Naked]

AWSOME!!!!! Great idea, excellent execution and write up! Having done car audio installs for 20 years this would have help sooooooooooo many classic car owners its not funny.(of course w/ the ipod it makes all that the more sense) i applaude your drive to make it work.
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[jeffros 58]

is there a way to make this work on a older radio like a sapphire Iv am/fm radio 6v ??

[kentosh]

[jeffros 58]

I tried to make this work on a sapphire Iv but found to hard to seperate the volume control out of it .so went to a buddy and found a type 1 am radio and this worked perfectly .thanks now have a old sapphire 1 that plays mp3 and the mp3 also has fm radio with it looks and works great !!!!!

[kentosh]

Well I'm glad it worked! I'd be interested to see a picture of how it came out if you have one.

[Rag00oll]

Digging up an old one here, but I tried this today and what do ya know... it works. Awesome!

[Mitey62]

Very cool. One thing to remember however, is that when running a stereo off of an ipod, and especially a 3.5mm headphone jack, is that without any kind of equalizer you're not likely to get "good" sound. If you're just running the single stock speaker, that's fine. If you're running aftermarket speakers though, you'll likely need some other... "bits"

Nice job, and thanks for the writeup!

[Rag00oll]

True, definitely not the best sound around town. But hey! It's better than AM talk radio all the time.

It's an excellent mod, and very simple for a sunday project. Took me two- 3 hours tops from sitting down at the kitcehn table to driving away with some tunes.

Oh. And it looks good.

[juniorvick]

great job.. wish i had the skills to do this... but for now ill just leave the newer head unit int he glove box

[phononocd]

I saw this Idea, and thought I'd try it out, but with a few modifications to the original poster's design. I used a switching jack, located in the glove box. My idea was that when you plug in a device, the original radio circuits will be cut off and the device will feed audio signal into the radio's amplifying circuit. I still used a cap and 2 resistors in the same sequence as the diagram pictured above. with high hopes, I put this all together, with three wires leading from the glovebox to the radio: a ground wire, and a wire that is connected to the amplifying side and one to the original radio side. when nothing is plugged in the radio and amp are connected, so in theory, the radio should work as it did before modifications, when you plug something in, the wires disconect, and connect the device that is plugged in to the amp side of the radio.
Last night I installed the radio (Motorola Sapphire 1) and the glovebox into the car. I turned on the radio with nothing plugged in to the jack, and I only got static over the speaker, I plugged in a portable radio in to the jack, and I got nice clear sounding music. I was happy with that, until just a minute ago, I turned the engine on. I could hear every spark broadcast loudly over the radio, no matter if anything was plugged in or not
I think that the wires that are outside of the radio might be picking up these noises like an antenna, and also are probably messing with the stock operation of the original radio
Does any one have any suggestions on how I could eliminate the spark noise from the engine?
I will mess with it today And see what I can do.

[BerylGreen63]

[pwmcguire]

[phononocd]

well, I re-examined my modifications, and noticed when I touched the wire that was supposed to connect to ground to an actual ground, it sparked! Obviously it wasn't grounding. Inside of the radio I had connected the wire to a brass like plate that was touching the inside of the radio. The multimeter told me that this clearly wasn't a ground. I took that wire off and connected it to a verified ground on the radio. After hooking everything back up, no engine noise is heard, it only needed to ground properly. The radio itself does not work like I expected it to, but I am happy with it. The sound from the plugged in device sounds clear as ever, and can be turned up or down using the stock radio in the dash.
My car is stock 6v with generator.
Thank you for the suggestions, but I got to fixing it before I saw them.
Also thanks to the original poster for spawning this idea.

[panicman]

At the risk of being "that guy" can someone translate the wiring diagram showing the add-on into English? I would love to make this mod to my radio, but the diagram is a different language, and requires some 'splaining for us non-electrical folks.

The diagram looks to me like it shows a lead running from the volume pot to a mini jack in series, out to two leads with 5.6k resistors, both leading to a common ground Am I seeing that correctly? Last time I studied a diagram like that was 20 years ago.
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[phononocd]

English, that diagram above sure looks like english to me.
The mini jack should have 3 prongs if you go with a simple non switching one. two of them are for the 2 stereo channels and must be combined for the mono radio. the other wire is ground, and must be connected to a good ground in the radio. to combine the two stereo channels, you wire a 5.6k resistor to each side of the prongs on the jack, then connect the other side of the resistors to a .1 capacitor. the cap then leads to the connection on the volume pot. Finding which connection on the volume pot was the hardest part for me. The volume pot had many different connections on it, for volume tone and on/off control. by using the multimeter I found out which set of connections was the volume section, and by tracing the wiring diagram for my Sapphire 1, I found that I needed to connect my new input into the connection that had a red wire on it. Different radios would obviously have different wiring designs and wire colors. I found my radio schematic in the technical section here on the samba.
Hope this helps!