Instructables
My family and I like to listen to music when we're outside playing with the kids or swimming in our small above-ground pool. We had a couple of old CD/Tape/Radio Boomboxes but the CD players didn't work and the old analog radio tuner was often hard to lock in on a decent radio station. After reading some of the instructables here, I thought maybe I would try to modify an old tape boombox to hook up an old MP3 player. That way I could load the exact music we want to hear and the radio would be digital tuning with favorite stations saved.
So here goes...
 
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Step 1: Open the box

C:\Documents and Settings\Daddy\My Documents\My Pictures\instructable\MP3 Boombox 004.jpg
We start by opening up the old tape player. There are screws in the back of the player that have to be taken out to open it up. Different players will have screws in various places, but this one only had four screws, one in each corner. (If you take out all the obvious screws from your player and it still won't come apart, be sure to check in the battery compartment. Sometimes there might be a screw or two in there as well. Also, note that some times, as in my case, you will have to press Eject to open/release the tape door since, at least on mine, it latched a part of the cassette mechanism and ended up keeping the front half from coming completely loose.)

Once its opened up, you'll need to find and remove any screws that hold the cassette mechanism in. Also, locate the tape play/record head since we'll use the wires coming from it as the input from the MP3 player.
Bill Bob2 years ago
hey a question about 6 wires coming from a cassette tape player head. This is on a 1999 gm delco car radio. I want to hook up to these wires to hook in an mp3 player. BUT, BUt - it's got 6 wires , not just the three that I've gootne to work with on other units like this. DOES ANYONE know how to figure out which three wires I need to tap into ??????
Kaiven3 years ago
I found pins 2 and 13 on my la3220 ic on my ghetto blaster... This may be the only solution I have left! But I still don't know where to attach ground? And are pins 2 and 13 corresponding to left and right? (or vice versa) I just need to know where ground is, any help appreciated!
Kaiven Kaiven3 years ago
Wait a sec... I found ground to be pin 1. But it doesn't work. And on the IC, pins 2 and 13 are output... so why would connecting the input from the MP3 work when connecting to the output? hmmm....
vader0ne3 years ago
I always tap off the volume control on the older recievers dont know about the newer ones,but wouldnt think there will be much diffrence...
mode14 years ago
can you tell me more about wires coming to that headphone output, can you tell which wires where goes? sorry for bad english
vincze4 years ago
Can't i just connect a 3.5mm jack to the wires going from the tape thingy to the board?
HappyDad (author)  vincze4 years ago
Hi Vincze, I think the output of the wires there would be too low; it seems it needs the pre-amplifier to be strong enough.
dman9774 years ago
Just a suggestion for "HappyDad" & those who have the same MP3...

Would it be possible to wire in a USB port and trim down the 7 volts to 5 with a few diodes? I have used those MP3 players before, and they have a built-in USB port on them. Sounds like it could work in theory, I just don't know (because I cannot try myself) if the player would go into MASS Storage Mode. If it doesn't, then you could run the player from the USB power.

Good luck.
HappyDad (author)  dman9774 years ago
Sounds like a good idea dman977, thanks!
etchasketch5 years ago
step 10Victory!!
I looked at the traces going to the volume control and they went through lots of capacitors and resistors and was very confusing.
I decided, what the heck, I'll just move the wires to the output side of the preamp, the LA3220 (pins 2 and 13), just for fun. Who knows, it just might help and if it blows something, too bad; I'm gettin' tired of fighting it.
CAN you provide a pic for us tech impaired?.....can you email one
please !
bezzymares@yahoo.com
HappyDad (author)  etchasketch4 years ago
Hi etch, sorry I'm just now getting back here.  I don't have the schematics any more.
sljubic4 years ago
Try to solder input wires directly onto volume knob slider contact midle one and you can easier adjust input level
jackbomber4 years ago
 I avoided the soldering and wiring( as I'm not electrically proficient) by buying a cassette adapter for about 5 bucks. cool instructable though. this is much cleaner than having the adapter wire hanging out the front. 
 you could have saved yourself a lot of trouble if you had connected to the main volume pot in the first place. Its about the oldest trick in the book,works everytime:)
sjlammer5 years ago
You can easily get a panel or chassis mount 3.5 mm jack from a place like allelectronics.com
qnzfinest5 years ago
can i use an ipod for this project???
yes you can!!!
pokey3025 years ago
I am trying to do this to an old Panasonic RX-DS18 but i am running into some problems. 1. I can not isolate the headphone jack for some reason. I have everything scraped away from it on the board but it’s still picking up sound (frustrating). 2. What source are you using for the wiring schematics? My radio does not have any manual switches so i am having a difficult time trying to figure out where to solder in the mp3 connection so it will bypass the pre-amps. 3. Thank you so much for the informative post. I can't wait to get mine up and running!
HappyDad (author)  pokey3025 years ago
Hi Pokey302, Sorry you're having problems. You might want to try the idea that jsmirnio99 below had. That seems like a simpler idea. On problem number 1, be sure to check both sides of the circuit board; sometimes there might be traces on the other side that need to be cut. On problem number 2, I just googled for wiring diagram for . Good luck :)
I am unable to go with the other idea because everything is digital including volume. I put the old radio back together minus the tape player. Think ill go with a different radio. (i have many to choose from) I haven't given up yet!
jsmirnio995 years ago
One of the easiest ways to add an input to any audio system is to use the existing volume control. You connect the new input to the center (wiper) arm of the controls and then still vary the volume with the knob. If you use a special 1/8" jack that disconnects one set of contacts when a plug is inserted you are all set. Plug in the jack and the new input is amplified. Unplug, and the system reverts to normal. (8~)
HappyDad (author)  jsmirnio995 years ago
That's a brilliant idea, jsmirnio99! I'll have to try that. Much simpler that what I did and would probably work much better. I bet that the volume control is likely on the pre-amp side of the circuit so that would probably work really well. Thanks!
patcroy5 years ago
Hi! I am a auto mechanic not an electronic guy. I was wondering why one could not just buy one of those cheap cassette adapters plugins for MP3. And to eliminate the tapedeck noise just open the tape deck electric motor circuit. Wouldn't it be cheap, quick and effective? Pat from Waltham PQ
Phil B5 years ago
One option would be to use capacitors to couple or connect the output from the MP3 player to the chosen inputs on the boom box circuit board. A capacitor allows the audio signal (a type of alternating current) to pass while blocking an overload from too much voltage (DC). Different sizes of capacitors may be used, but a 1 microfarad capacitor should work without distortion. They are usually electrolytic (polarized), so pay attention to what is + and -.
Great!!! I'm gonna do that with my car radio. Thanks. Hey
Jeddychan5 years ago
hey guys, I'm trying to make this for myself, but Ive gotten snagged on some things... I'm pretty sure I found the right schematics for my IC, but I don't know where I should hook up my left channel and right channel wires (aka headphones with the speakers cut off). Heres the schematics. If someone could help me Id really appreciate it. =D
heres the picture
IC.bmp
Could you shut the MP3 player inside the cavity where the tapes used to go, for total portability?
110100101105 years ago
in the part with the resistors - add resistor from each channel to ground instead of using higher value resistors use resistors about the same as the existing ones (smaller for lower volume) and equal on the 2 channes
damasta6 years ago
or you buy an mp3/cd tape (so you don't have to modify your player)
Sandisk1duo6 years ago
did you check the voltage of the motor? it might be close to 1.5v if not, you can get one of those variable regulators at radioshack, they are easy to set up and they are reliable, need help? Tell me! P.S. gr8 instructable
HappyDad (author)  Sandisk1duo6 years ago
Hey Alex, thanks! Yeah, I checked the motor voltage, it is about 7 volts. So I do plan on using one of those voltage regulators to drop it down to 1.5v. thanks again!
Your welcome!
DoubleM6 years ago
I read your instructable thinking"what if my old mp3 player will be different then yours,I will mess it all"but when I saw your final picture,the mp3 player is THE EXACT SAME!Maybe I'll try this!
HappyDad (author)  DoubleM6 years ago
Hey MM, yeah cool! It works great. I've also used my PDA as the player and hooked the headphones plug of it to the project. Its really handy. Hope it works for you too. Good luck!
bootdsc6 years ago
This is a great way to add an audio input for old devices that lack this ability. I have done this before on a radio just like yours sept i fully removed the amp and used it to make amplified headphones to help with the crappy output volume of my ipod shuffle. great Instructable!
HappyDad (author)  bootdsc6 years ago
Cool, sounds great! Thanks, bootdsc!
HappyDad (author) 6 years ago
Hey CameronSS, cool! I wish they would have had a sale here when I got it! Great deal!
CameronSS6 years ago
You have to pay $7 for a Harbor Freight multimeter? Our Harbor Freight has them on sale virtually all the time for $1.99. The set of leads is worth that...
idogis16 years ago
going to start this, tell ya how it turns out
HappyDad (author)  idogis16 years ago
Hey idogis1, great! I look forward to hearing how it goes. Good luck!
HappyDad (author) 7 years ago
This is my first Instructable. I hope it is useful and helpful. A big thanks to unknownuser2007 who helped me get it working better!