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!!!