by Jeremy Schrag
The automotive CD changer: a natural progression in car audio, it allowed a vehicle owner the chance to load up several discs and hit the road. In the mid-nineties, Chrysler decided that the CD changer was a good thing to add to their list of options on the new Sebring, among other cars. But how to implement it? Most people still wanted the option to play cassettes as well, so it would have to be a cassette head unit, rather than the single CD in dash head unit available at the time.
Chrysler turned to Alpine and Mitsubishi to help solve the problem of coming up with changer controlling head units worthy of placement in their vehicles. Today, I'm looking at Alpine's entry, found in the dash of a Sebring; as you can determine from the non standard mounting points on the sides of the above deck. This deck interfaced with Chrysler's six disc trunk mounted changer of the time, also built by Alpine. These were also found in the cloud cars. I will look at the more mainstream Mitsubishi deck in a future article.
Here, we see the part number and supplier code of 26777, which confirms Alpine as the source of this deck. It bears a remarkable resemblance in this view to the Infinity IV single CD head unit, also built by Alpine. In fact, this is the first and only Mopar cassette unit I know of that is completely built by Alpine. Yes, the company had provided parts to Chrysler's Huntsville Electronics division on numerous occasions, but never complete cassette head units.
This is the official Chrysler part number of this deck: 4704302. A quick online search pinpoints the unit's sales code as RBS, though this code is not actually found anywhere on the unit itself.
A look at the back of the deck shows us the familiar black and gray connectors for the main harness, the antenna connector on the top left, and the ground bolt location in the center. Down in the bottom right, we have the round 8-pin DIN connector for the CD changer and the two pin CCD bus connector, enabling such amenities as steering wheel controls and diagnostic data transfer.
All units that have these extra two pin connectors to my knowledge receive information on display dimming through this connector as well. When you turn the headlights or parking lights on, the display dims normally. But some vehicles have a way of brightening all the vehicle displays for use in the daytime [by moving the rheostat up to the first detent; the second detent turns on the interior lights]. This connector is how the deck receives this information. Left disconnected, the deck simply dims the display normally with the headlights on, and will not brighten it until you turn the exterior lights off.
We will begin taking the deck apart now, so you can see what is involved with servicing it. Be warned - this is one of the most complicated decks to service, simply because it is hard to disassemble. I will show you how to do it all the same.
Red arrows indicate the faceplate screws. Remove them, and the corresponding screws on the other side. Pull the volume knob off, and the bass and treble knobs as well.
Once all four screws are out, unclip the faceplate on the top and bottom and remove it.
Now, we'll remove the two screws holding on the top cover, and remove the top cover. It is hinged at the front of the deck, so just pry up somewhere at the rear of the deck to pull it off.
This is the "busy side" of the unit - the heatsink to which all major heat producing parts are bolted. You must remove all screws arrowed in red to do anything else inside the deck. It is best not remove the blue arrowed screws until you are able to pull the heatsink away.
This is why - a power resistor is bolted thus to the heatsink as well using a separate piece of metal. There is also a strain relief attached to one of the screws. Hold this assembly in place while you remove those blue arrowed screws so that you don't pull on those wires.
Now we have the power resistor and heatsink removed, and we can get on with taking the deck apart further. Note the large beige connector visible in the center of the picture - this joins the two circuit boards together.
Now, we'll take out the upper board, which has all the amplifier chips (Toshiba TA8233H) and some of the voltage regulation components. Remove all screws in blue and remove the ground bolt mount in the bottom center. Bend the twist tabs arrowed in red so that they line up with the slots in the board. Then, apply pressure near that beige connector I pointed out earlier, arrowed here in yellow. The board should pop right up and off.
Re-solder any dubious joints you find, especially the joints around the parts that were bolted to the heatsink. They are along the left edge of the board in this shot.
From here, we'll move on to the cassette module. This is one of the most aggravating cassette modules to work on I've seen in a Chrysler head unit, though it still takes a back seat to the Infinity II and III. Remove the screws indicated in red. Then, pull the module straight up and out. It is plugged into the bottom board near the lower left corner - this is where you will need to apply the most force.
Now the cassette module is out, but there is more work to do before we can even clean the tape head, capstans, and pinch rollers. Do not rely on the self cleaning mechanism - after all these years it is likely to be all but useless.
This module has a metal cover on it we need to remove to access these parts more easily.
Remove the two screws in red. Then, gently pivot this end of the cover in the direction of the blue arrow. Let me show you the other side now.
On this side, the cover is only secured by one pin, indicated in blue. The red pin is part of the loading mechanism. As you pivot the cover up, work it in the direction of the blue arrow so that it clears both of these pins. Then, you can take it off.
Like so. Now, we have plenty of room to get at the parts we need to clean. But I won't stop there, I will show you how to replace the cassette belt.
And this... is where the level of difficulty makes a sudden and drastic jump. The belt is not easy to access at all. See that big metal cover over the whole bottom of the module? That has to come up. You remove it by prying it up on the right side of the picture, and then it pivots up on tabs indicated by the black arrows.
But before you do this, you should de-solder the silver looking ribbon cable from the circuit board at the back. You don't have to, but it makes things a bit easier. You also must remove the screws arrowed in red, and the very tiny nylon retaining washer pointed at in blue. I'll give you an extreme close-up of that washer now.
This is very easy to lose, this washer, being very small indeed. My method of removing it is to place my thumb over the shaft is is installed on as I pry up the cover. The washer will pop right off, but won't fly away as long as my thumb is holding it. Of course, replacing the washer later is a whole other kettle of fish... I used some dental picks to guide it where I wanted it to go, and then used my thumbnails to press down on either side so it would pop back into place.
I also used a dental pick to help with the de-soldering of the ribbon cable, as you can see here.
Here, the bottom cover has been removed and the cassette belt is right there, easy to replace. Note the gear on the shaft still attached to the bottom cover - you will need to guide this back into place later, but it is not that difficult.
A close-up of the cover. The red arrow indicates the reel sensor and LED. Infra-red light from the LED is pointed down through the deck onto the back of a black gear, which normally turns when a tape is playing. Little reflective spots placed at intervals on the gear then bounce the light back up to this assembly, which detects the light pulses and tells the CPU that yes, the tape is playing. When the end of the tape is reached, the gear stops, the pulses stop, and the deck knows to reverse playback.
So, if your deck is reversing constantly, look here first. It's not unheard of for these parts to fail.
Blue arrows indicate the microswitches that tell the CPU what position different parts of the mechanism are in. Be very careful when you reinstall this cover, because one of these switches needs its plunger depressed to clear the mechanism as you put the cover back on. Let me show you.
The red arrow points directly at the black microswitch plunger, and blue indicates the direction to push. You just need it to clear that metal tab below the switch plunger, and the cover should snap back in place without a lot of fuss. I used a small jeweler's screwdriver to do it, but a toothpick would do the same job just as well.
Now, we'll get to the faceplate circuit board. There are four twist tabs holding it on, and the one in the upper left is soldered on. De-solder that one, and then just pull the board forward and off. It won't fight you much, as long as the tabs are lined up with the slots in the board.
The back of the front panel PCB. Unlike other Mopar decks, the illumination bulbs are not mounted to twist lock bases for easy removal. They are all soldered in. That said, they are the same 12 volt 3mm grain of wheat bulbs you find in most Chrysler decks. They can be sourced from eBay, specialty electronics suppliers, and sometimes hobby shops that sell model train accessories.
Note that this model has amber (orange) filters over the bulbs, to provide the distinctive amber illumination found in the Sebring as well as the Neon. You can find these filters in other colors, as well, though it's not as easy as finding the bulbs.
Let's move on to the hard part - removal of the bottom PCB. Why is it hard? Well... blame that two pin CCD bus connector. You will have to break a spot weld and bend the back of the housing to clear that connector so that the board will pull up and out. More on that in a bit.
First, the red arrows. All point to twist tabs that are soldered in. De-solder them all, and then bend them in line with the board slots.
Note that this particular twist tab also holds a strain relief for the wires of that power resistor... this is soldered in place and will have to be removed too.
A close-up of the tuner module and antenna connector. De-solder the tab in red, then bend it back against the side of the unit. De-solder the antenna wire and ground braid at the positions arrowed in blue. Unscrew and remove the antenna connector altogether.
Note that while you can also de-solder the ground braid at the orange arrow, I like to leave it in place. That way, you can just pull up on the ground braid to help remove the PCB itself.
Now, we need to crack that spot weld. It is indicated in red. Just get a screwdriver or something in between the two pieces of metal and pry them apart. It should break fairly easily. Don't worry, the deck will go back together properly - the deck's screws will hold the joint in place once the rear cover is bent back into position.
Now, just remove the PCB. Up and out it comes, guided by the two cassette module mounting posts you see in the above picture.
Before we go on, some of these decks are known to suffer the infamous blank display issue. The parts responsible for supplying voltage to the vacuum fluorescent display are in this corner of the board, and commonly plagued by bad solder joints. To make matters worse, many parts are surface mount, requiring much care and patience to re-flow. If you are not comfortable working around such small parts, bring the deck to an experienced service technician.
Here's the underside of the board. Re-solder any joint that looks at you funny. Pay special attention to the bottom right corner - this is where the parts are I showed you in the previous picture. You can see that this deck has gotten a little warm in that area.
Last but not least, remove the rotary encoder (volume knob) assembly and touch up the solder joints here as needed. It comes off with only a single nut removal. Note the locator pin - it fits into a hole on the front panel to lock the encoder into place.
All done? Good. Now, just put it all back together. Don't forget to bend that rear panel back into place.
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