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1st Gen FTW - It's AutoMedic!
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Discussion Starter #1 (Edited)
Well, I’m at it again… I just can’t keep my hands off of little projects I’ve had saved up…

I’ve got a stereo head unit from a flooded car because I needed to swap faces with another unit I got from another yard with the wrong mounting tabs.

I’ve got a little project in the back of my mind, and here is a hint…

First of all, here is the stereo unit in question…



The flood stereo face plate cleaned up o.k., and was put on my good stereo and installed in the car (as seen above). I took the rest of the flood stereo and put it on a bench and took it all apart…

Below is the break down of the stereo. I just took it apart on my own, then found this discussion at Allpar - Tweaking the Chrysler CD-Cassette Combo Player. If you want to take yours apart, use his guide.


Here is the stereo with the face plate removed:



Top cover off…



Here is the top of the unit showing some of the water damage and the model number. Interestingly enough, this is the bottom sticker, the top cover had been re-stickered at some point, and the top sticker I couldn’t read. There is writing on the inside to suggest it was rebuilt at one point.



A few screws, and the CD unit will come out. This is as far as I will need to go when I do the mod I have in mind…



But… I had to dig deeper to discover what I really needed.

Here is the back cover off.



The right side of the unit is the AM/FM tuner. Here it is removed.



Here the front panel is removed



The left side of the unit is the power supply on the bottom, and the amplifier on the top. The left side of the case is the heat-sink for these.



Here is the front frame of the chassis removed.



Here is the main control board, signal processor board, and amplifier removed from the bottom of the chassis, exposing the tape deck and power supply.



Here I have removed the Amplifier from the control board. The twin red wires run from the amplifier to the signal processor board. The audio is sent from the processor board to the amplifier as 4 channels.



Here the signal processor board (the smaller board) is removed from the main board. The bone colored connector on the bottom left is the primarily where audio is fed to the control board from the main board. The other connector is primarily digital control.



Here is the main control board. The white ribbon cables seen on top are for the tape deck (left) and CD player (right). The AM/FM radio connector is at the top left corner, facing left. The two connectors at the top go to the front panel. The large white connector on the far right is the main power connector from the power supply, and the smaller white connector (thin, may be hard to make out) is the power connector for the amplifier.



Here is the main board turned over… the front panel connectors are at the bottom of the screen now.



Here is the lower chassis, with the power supply and tape deck. You can really see the water damage here.



I removed the tape deck and here is just the power supply.



The rear most board of the tape deck sub assembly is the tape control board. This is what controls the logic controls for fast forward, play, eject, etc.



The other board on the tape deck is the pre-amp and Dolby Digital (DD) signal processor board. This board gets signal from the tape head (attached in this photo) and gives it to the control board.



From the bottom of the tape deck unit comes the tape drive mechanism (several gears are NOT shown in this picture).



The bottom of the spindles that turn the tape have reflective ‘spokes’ that are seen by sensors mounted to this board. There is also a micro switch for tape sensing here – so the player knows there is a tape to play.



And here are all the little parts left over I didn’t show you the removal of…



Well, that’s it, the entire thing broken down… most of it came apart with a Phillips screw driver, but some of it was broken to take apart, some of it was un-soldered, and some of it was just little twist tabs to bend out of the way. I also broke down the CD player, but nothing noteworthy in it. Because this was a junk unit, I wasn’t concerned about destroying it… but I did learn what I wanted to learn… I washed the tape control boards and have some more pictures…

This is a detail shot of the DD control board… the black chip just off screen is the pre-amp. This processes the magnetic pulses from the tape into audio signal. This is fed to the DD control chip, a Hitachi HA12134AF. From this chip, the audio is sent out.



If you were to zoom in on the left most edge, you can read the letters MBPFGLD9R. This is not a model number, but rather this is the pin-out for the connector on the under side. The only letters I’m concerned about are the G, L, and R. Tracing the green traces on the board, the G seems to be a common line on the board, indicating possibly a GROUND path. L and R…? I wonder… So, I trace them back, and they terminate under the Hitachi chip.

I removed the Hitachi chip rather crudely, just by clipping the surface mount leads with a pair of scissors on my pocket knife (I use that knife EVERYWHERE).



Sure enough, the lines for L and R terminate under this chip. I went out and Googled the chip to find a spec sheet, and sure enough, the third pin from the right, on both sides of the chip, are the PB out. The chip is designed as a DIP (Dual Inline Package), and each side is identical and linear. Signal comes in one end, is processed, and outputs from the other end.

So, I followed these tracings to the pins, and then through the plug to the control board. Here is the front of the control board. In the upper right corner, is a small horizontal connector from the DD signal board.



Turning the board over, I follow the traces on this side. The L and R lines do not go through the control chip or any other components on this board, they go right to the ribbon cable connector on the other side of the board



I followed the traces again on the ribbon cable and up to the main board. From the main board, they do not go through any components, and go right to the main signal processor board. Here they pass through several components, and through some IC chips. This is where my trace of them ends, but signal on this board eventually passes to the amplifier.

So, I have surmised… if I were to tap into the lines between the DD chip, and the main audio signal processor board, I can feed my own signal here… I have to fool the tape deck to think there is a tape in place, but that is as simple as linking the two spindles to each other (rubber band) and closing the switch for the tape sensor.

To get my own signal fed to the audio board, I have discovered that I can stop at this step shown below, and tap into the ribbon cable connector for the tape deck that is exposed.



If I get this project off the ground in a working unit, I’ll post back… This may be fun!!!


:woot:
 

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1st Gen FTW - It's AutoMedic!
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Discussion Starter #3
Well, I acquired the next parts for this mod...





It is the Audio/USB Board for a Toshiba M30/M35 Laptop...

I planned originally on just using the Audio ports in my dash to link to my head unit... but when I got to looking at the USB portion, I think I'll end up wiring the USB for charging ports - it would free up my 12V socket again.

So, now I just have to figure out where I'll put the outlets, and if I'll mount the USB in the same place I mount the audio ports. As you can see, the audio ports stick out farther than the USB does on the board, the original laptop had a different offset in the case for each type of part.

More to come as I can do it.
 

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1st Gen FTW - It's AutoMedic!
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15,449 Posts
Discussion Starter #5
Yup! That's the idea. I MAY have to perminatly install a tape adaptor into the tape bay, but honestly, it would look MUCH better than having a wire falling out of the tape player looking like a thermometer under the tounge... And, I think that the audio signal would be cleaner too.
 

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1st Gen FTW - It's AutoMedic!
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Discussion Starter #7
Do you have any hands on experience with the level of electronic work I'm doing? Not that it is really THAT deep, but it is deeper than installing a new stereo... I'm not designing a new circuit, but still.
 

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1st Gen FTW - It's AutoMedic!
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Discussion Starter #10
I ended up having to move, and so all of my mods got put on hold... right now they are all sitting in the back of a moving truck that my dad bought for me (temporarilly, I have to sell it and pay him back at some point). So, for now, no mods in motion... but I did buy some RCA plugs to put in the rear of the center console for adding audio and video inputs (video for the headrest displays) and then also bought some USB ports and audio ports from a laptop audio board to add plugs to the dash... will likely only use the USB for power (phone and MP3 battery charging, etc)...

But no, no more progress. I was in the back of the truck yesterday, and opened the boxes to look, to keep myself infected with the mod bug... *grins*
 

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I ended up having to move, and so all of my mods got put on hold... right now they are all sitting in the back of a moving truck that my dad bought for me (temporarilly, I have to sell it and pay him back at some point). So, for now, no mods in motion... but I did buy some RCA plugs to put in the rear of the center console for adding audio and video inputs (video for the headrest displays) and then also bought some USB ports and audio ports from a laptop audio board to add plugs to the dash... will likely only use the USB for power (phone and MP3 battery charging, etc)...

But no, no more progress. I was in the back of the truck yesterday, and opened the boxes to look, to keep myself infected with the mod bug... *grins*
lol cool
keep us updated !
 

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This brings back memories of my pre-LH days. I had that same head unit in my 1996 Caravan. (yeah...I drove the parents old van in high school....hey, better than the bus right?)

The pinout is as you think on the boards. I think the 9 is a positive voltage rail. I bet you'll find 9V between it and ground. I also bet you'll find a 7809 voltage regulator in this thing somewhere. 78xx (and its negative 79xx brother) are three pin ICs that look like transistors. The bigger ones are usually mounted on heatsinks as they are rather inefficient (excess voltage is merely done away with as heat)

The three pins are in, ground and out, not necessarily in that order but usually.

The numbering format is as follows 78xx or 79xx. The xx refers to the designed output voltage. A 7805 is a +5V regulator, a 7812 is a +12V regulator. The 79xx regulate voltages that are negative with respect to ground. (ie, -5 for a 7905 and -12 for a 7912)

With that aside.....it you wanna be REALLY cool, figure a way to keep the tape but add a tape/aux switch with everything neatly installed in the dash. I never got around to doing that unfortunately. If I had more free time I'd mod my friends Jeep stereo that way.

As for the water damage, the best way to clean the boards is with a bath in isopropyl alcohol and an old toothbrush. Once you have that clean, rinse with DISTILLED (not drinking...steam distilled!) water and let dry for 24 hours.
 

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1st Gen FTW - It's AutoMedic!
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15,449 Posts
Discussion Starter #16
UPDATE - Nothing to report - I still have my parts to mod it, but with new jobs, chasing my wife and kids around, and then now the ND winter, nothing has happened with the car.

HardwareGuy - When I get back into this, I'll see what I can find from your notes - I apprecate it! And yes, I do plan on putting together this mod as a tape/aux using the phono socket as the switch.
 

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here's an idea for you, they make 12v plugged pieces that you plug a USB Flash drive with MP3's on it in the device and then it plays them, and it has an FM transmitter on most of them, maybe you could make another switch to switch between the audio jacks and this usb MP3 player mod and be able to use one USB drive to play MP3's Straight from your flash drive.


wouldn't be too hard to mod, the circuit boards for these devices are really small, and most of them even come with a remote, take it apart, find the routing on the board that sends the audio signal to the FM transmitter part of the device and solder 2 stereo wires into those lines then into your secondary switch, then you just need to detach the provided USB plug for the device, solder some wires for an extension of the USB plug or simply just use a small USB extension so that you can mount it on the face plate, and put all of these pieces where the tape deck part Was at, run power to the device from the internal power points in the head unit, and extend the IR sensor for the remote if it has one and WHALA!!!!






i modded one of these devices i'm talking about so that the power to it runs off of USB instead of 12v for the vehichle and put it next to my computer, and i have a split line for the speakers plugged into it so when i'm listening to music on the PC or watching a movie i can turn my onkio 7.1 surround sound system to one of the FM stations of my choosing and listen to my PC with excellent clarity :D
 

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I'm interested in this mod as well seeing as I'm going to try to keep my intrepid looking stock as I fix her back up... Do you have any pictures showing exactly what needs to be soldered and where? I may steal this mod from you :p
 

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1st Gen FTW - It's AutoMedic!
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Discussion Starter #20
With my car DOA in North Dakota after I moved, I put all mods on hold - but once I get a power plant back in her, I'll pick back up with where I left off.

Basically with out showing you wire colors, all of what you need to do is in there.... but I'll finish this mod in the future...
 
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