Line-in on OEM radio, a 9-hour-straight project...

Falcon4 · Post by **Falcon4** » Sat Feb 16, 2008 8:22 am

I'm too dead shot tired to think of how to write up a coherant topic right now, so bear with me... I just had to come to the first place I would think would be interested in such a thing, and report my success... call it sleep drunkness.

So anyway, what I did was first get tired of a car stereo that's too broken down to do anything properly, it can't play radio (it loses tuning after about 5 minutes of playing), and the tape player sucks. But the tape player's the only thing that's reliable. I just HAD to make it better. The tape player's an individual component. How can I jack into it?

I managed to rewire and rebuild some components to retain _all_ the functionality of the radio, while adding a neat little line-in jack.

I decided to start taking pictures after I realized "holy hell, this is coming out pretty good". Only thing I regret was cutting a board trace I thought was going to be a problem, then realizing later I had to connect that wire somewhere else anyway... and coming back to realize that trace I cut was one that would've come in handy in another part of the project. So I had to wire over the trace. D'oh, stupid...

So without further adeiu (sp?! i'm too tired for sp!), behold the pics.

Uh, side to side:
7: The finished product, ready to box up!
5: Testing to see which side is left and which side is right, this song has a great separation at the beginning that makes it easy to hear which one I'm listening to. Plus I was tired.
6: Turns out I need to jumper these two wires (blue and red/white I think, but click pic to be sure). Not sure their exact function, but one had voltage removed when the deck ejects, and the other had a constant voltage of the same level that pin jumped up to when the deck was operating, so I picked those two. It turned on the amp, I'm happy.
4: All the wiring all set and ready to test!
3: This junction permanently enables the "Search" function so I don't lose it when I re-assign the Search switch to line-in on/off.
2: Installed, I even had to carve some of the metal case out to fit the damn jack in that tight space. Oh, did I mention I had to carve out some of the PCB too? Hence the extra wires... replacing cut traces.
1: The rewiring of the front button board. It lets me switch line-in on and off with a shiny little "On" LED. The DPDT switch for the "Search" function worked incredibly well as a power and override swtich for the tape deck.
8: Me, extremely tired and too out of it to realize this is a shitty picture, showing off my creation.

All in all, yes it took 9 hours of straight, nonstop (as literal as it can get) work. I'm starving, thirsty, and tired. But I couldn't put the thing down. It's a neverending challenge

More back story tomorrow when I'm, uh, sober, and have a chance to actually test it in the car. It works great on the bench!

Xanth · Post by **Xanth** » Sat Feb 16, 2008 3:10 pm

If you can make a decent write-up for that I would like to host it on my site, I know other people have attempted that mod and are interested.

I always like adding functionality to a stock unit, good work :thumbleft:

Falcon4 · Post by **Falcon4** » Sat Feb 16, 2008 7:19 pm

Woo... a write-up? I dunno, crunching 9 hours of work down to a single write-up may be an exercise in futility... then again, I can't imagine how many of those 9 hours were spent reverse-engineering the wires with absolutely no web help whatsoever...

Seriously, I couldn't find shit about that stereo online. Nothing. I had to go entirely off my multimeter and headphones to figure out what wires did what, then from there figure out how to make it work the way I needed to. The first challenge was figuring out of it were even possible with a front panel that tightly packed with light tubes and controls, none of which I wanted to end up breaking. There was only one place it would really fit, and it also made logical sense with the setup I wanted to use.

I took the car and radio out for a test drive today. I couldn't possibly be happier. The input volume has to be kinda high, but I think that's normal for line-in (my iPod's line-out, when I get the cable back, is pretty much maximum volume, as the new stereo line-in seems to like). But the switch works perfectly. I wasn't expecting a "direction" light to illuminate when it's in use, but it doesn't hurt anything.

I first tested line-in of course. I activate it by switching the "Search" switch to "On", which lights up the light (that was actually easier to do, electronically speaking, than I thought) and switches the radio to Tape mode by tricking the stereo into believing a tape is inserted. The switch also disconnects the tape deck's power so it doesn't run the motor. The problem that presented is that since the tape deck is powered off but the radio thinks it's on, it's expecting some kind of signal to turn the amp on. I fixed that by crossing two wires together that seem to accomplish that pretty well (in retrospect, I think it may be the CrO2/Normal switch wiring that has to be in "some" position in order to turn the signal on... *shrug*). The switch, when switched to "On", does two things: it switches the 12v tape deck input over to the "On" LED instead of the tape deck, and it grounds the "tape present" wire (which, due to the lack of power, means nothing to the tape deck).

When the switch is in the Off mode, the radio works fine (or as fine as mine can get, it still de-tunes after about 5 minutes, grr). It switches the 12v power back to the tape deck and un-grounds the "tape present" line. In this mode, the tape deck has full functionality and works just like original (except for the lack of Search, which is permanently enabled, no reason to disable it really). I tested this with my old tape adapter, which works as well as usual... with just some now noticeable distortion (since my car radio was always my best stereo system, I had no point of reference!).

Next, when I get bored, I'll see if I can take a crack at that writeup. Meanwhile, I am totally ecstatic that I actually pulled something as complicated as this off.

(Crappy cell phone camera pic, sorry, didn't bring my real camera. Click for bigger.)

(edit: Yeah, the EQ still works too. I think if I just bypassed the radio/tape circuitry completely and went right for the amp, I'd have the problem that the EQ wouldn't work. Also, what's up with the long delay when posting? I think the forum database needs to be optimized...?)

p8ntman442 · Post by **p8ntman442** » Sun Feb 17, 2008 9:35 am

very cool. This will be a hugh hit in the fiero community (I suggest buying and doing this mod and selling them to Fiero owners). The reason it will be a bi hit is that its cheaper than an aftermarket deck, and requires no thinking to install. Fiero owners love cheap and easy. Im guess you could just fm modulate a signal for just as cheap.

The detuning thing sounds like a bad component on your tuner circuit, probably voltage regulator or capacitor.

Falcon4 · Post by **Falcon4** » Sun Feb 17, 2008 12:36 pm

Actually, it cost me about $3, the cost of the jack ($1.50 if you only count the one jack in the 2-pack they sell)... and it's definitely not a no-brainer, you've got to be REALLY fucking good with a razor, drill, and a soldering iron.

Shaun41178(2) · Post by **Shaun41178(2)** » Mon Feb 18, 2008 12:04 am

awesome dude. I love posts like this! Nice work

Falcon4 · Post by **Falcon4** » Mon Feb 18, 2008 1:29 am

I ended up choosing the wrong value resistor for the "ON" LED for the mod (basically stole and re-assigned one of the resistors I had to chop through to fit the jack in), not having any formal electrical training and only raw logic and a JavaScript Ohm's Law calculator to work from... I ended up burning out the "On" LED. Shit. So I don't think I'm quite ready for that guide, but I'll be goddamned if I'm going to tear apart that whole damn radio again any time soon to fix it.

Hey, it's really freakin' awesome to hear two of my ol' "Friends" (i.e. people that probably wish I would get carpal tunnel and stop posting online at all) actually agreeing with one of my posts. I guess I did something right for once :thumbleft:

Pyrthian · Post by **Pyrthian** » Mon Feb 18, 2008 11:25 am

http://www.fiero.com/forum/Archives/Arch ... 73268.html

Unsafe At Any Speed · Post by **Unsafe At Any Speed** » Mon Feb 18, 2008 1:29 pm

Interesting project. :thumbleft:

p8ntman442 · Post by **p8ntman442** » Mon Feb 18, 2008 8:50 pm

Falcon4 wrote:
Hey, it's really freakin' awesome to hear two of my ol' "Friends" (i.e. people that probably wish I would get carpal tunnel and stop posting online at all) actually agreeing with one of my posts. I guess I did something right for once :thumbleft:

I have a short attention span, so that means if your not acting like a tard for a while, your working with a clean slate in my book.

Looks like the topic posted above covers all the steps necessary to complete. Its cool you did it alone.

Alexander gram bell and that other guy right.