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by Jeremy Schrag
Not long ago, we explored the inner workings of Chrysler’s first ever in-dash CD changer, a four disc model from Mitsubishi used in both standalone and integrated configurations, that was somewhat problematic when it came to reliability. With ever more demanding buyers, Chrysler decided relatively quickly to discontinue those, and found a manufacturer able to provide them with a six disc model.
Today, I’m looking at this very CD changer. Found in the dashboard of a 300M, this is a popular model among those wishing to keep the factory system while adding the ability to store two more compact discs.
Before beginning this article, I tested this changer for working order using my RBB cassette unit from a newer Concorde. This deck originally came to me with the four disc external changer. Not only does this six disc model work with that deck with no modifications, it is completely plug and play. It is reported to also work with decks as new as 2006, so you are not limited to only a few years of compatibility around the new millennium, either.
Now, it is important to note that while it will function with those decks, installation options are still limited. A changer found in the dash of a 300 will not bolt into a Caravan, for instance. This is due merely to the mounting ears being different. Electrically, they will still work.
The external sides have few screws to worry about when it comes to disassembly. On either side, you have two screws each to hold the faceplate on.
The bottom panel has no screws at all, only plastic clips used by the faceplate to hold on to the housing.
The top panel is our first stop in disassembling the unit, and is held on by one lone screw. Remove it, then pry up the cover from the back of the unit.
The label on this unit has a couple of interesting features. First, there’s a pinout diagram of the interface connector on the back. This again confirms that it is 100% compatible with the four disc models and their cables. Second, we have a supplier code we’ve never seen before: 42774. It’s taken me some research to determine that this changer was apparently sourced from Delphi (formerly GM’s in-house parts company).
On the back panel, we have three screws of note. The red arrowed one holds the changer mechanism to the housing, and is one of two that hold the accessory ground bolt bracket to the back. You don’t have to remove that bracket to service the mechanism, but I’ll do it anyway to allow for better placement for pictures.
The blue arrowed screws hold two transistors to the housing for heatsinking. We’re not going to worry about those yet. In fact, if you are only working on the changer mechanism, you don’t need to bother with them at all.
With the top off, we can see the mechanism itself. I must confess that it seems more robust than the Mitsubishi four disc changer mechanism.
If you have one of these, and it’s defective, you may be wondering how you may find a replacement. Actually, that’s not as hard as it may seem. In my research, I have discovered that this has been a very popular changer mechanism; Volvo, Ford, and General Motors were all using it. You can find new mechanisms online as I type this very sentence [in late 2013]. A Google search for “Delphi 28000024” may help. Chrysler also used them in the RBQ six disc in dash head unit with RDS (Radio Data System) support. I have yet to locate one of those units to profile.
Replacing the mechanism is not quite as simple as ordering a new one up and dropping it in. You must use the interface board from your old changer with the new mechanism, because different auto makers have different ways of getting the same parts to talk to each other. Delphi may have built this unit using an off the rack changer mechanism common to a lot of other changers, but the control circuitry is a custom job for Chrysler. I’ll show you how to remove that circuit board a bit later in this article.
Meantime, we’re just going to pull the faceplate off the unit now. It’s very easy, just remove the four screws, release the two plastic clips underneath, and pull it straight off.
You can remove the faceplate circuit board, but there is very little you will be able to service on the other side. To get the board out, release the three clips arrowed in red and pop it out.
Note that when you go to re-install the board, you will have to make sure the buttons on the front are not depressed first. If they are, the board won’t go back in properly. It’s a little tricky, but not impossible.
Here’s the board removed from the faceplate. As you can see, all illumination lamps are microlamps in surface mount bases. These are very hard to replace, and I currently do not know of a source for them. With some effort, standard 3mm grain of wheat microlamps with new blue sock filters might be adapted to fit, but it’s a gamble and not a job for the weekend warrior with a soldering iron that rarely gets used.
Now, we’ll remove the changer mechanism from the housing. You did remember to remove that single screw on the back panel above the accessory ground bolt, right?
If so, remove the four screws arrowed in red.
Next, gently remove the changer mechanism and set it to the side like this.
Release the retaining tabs on the ribbon cable connector to unlock it, and pull the ribbon cable out of the connector. This image shows the connector in the unlocked position for your reference.
Our next task is to remove the rear mounting bracket for the mechanism. Remove the two indicated screws, and set the bracket aside.
Before we get into the mechanism itself to free your stuck discs, I’ll turn the mechanism over and show you the interface circuit board. We’re going to remove it, so you can swap it to a new mechanism.
First, observe the red arrows. De-solder the tab at the middle one, then bend the tabs away from the board. Also, de-solder the joints indicated by the dark blue arrows. Make sure those two in particular are completely free of solder... these join the roller motor leads to the interface board.
Disconnect all five ribbon cables indicated by cyan arrows. These work the same way as the main ribbon cable you’ve already disconnected.
Now... gently, gently, gently lift up on the board on the side where the red arrows are. Gently work it slightly forward to clear the board’s tabs from the slots in the very bottom of the picture. Ever so carefully, pull the board up and off. It will stick a little bit by the blue arrows, simply because those motor leads are a little stiff.
Wipe the sweat off your brow, let out a sigh of relief, and set the board aside on an anti-static mat. An old anti-static bag used to ship and store computer parts will suffice.
To install the board into a new mechanism, proceed in reverse order. Don’t forget to reconnect all five ribbon cables. It’s easy to miss that one in the bottom middle of the picture.
It’s now time to save your CDs from a damaged changer. With the mechanism facing up as in the picture, disconnect the electrical connector arrowed in yellow. Then, take a Philips #00 screwdriver and remove all screws arrowed in red. There are eight of them.
Note the orange arrows. These are approximate locations where two pins join the top cover mechanism components with the parts in the lower section of the housing. You may have to manipulate these little parts around to get the top cover back on the unit, should you plan on re-assembling the mechanism. I’ll show you those a bit more clearly in a bit. It’s not all that hard, unless you decide to play with the gears in this part of the mechanism while it’s apart.
Now, pull straight up on the top cover, and it should come right off. I must say that this is perhaps the easiest changer mechanism I’ve seen yet when it comes to ease of access. It’s not easy, just less difficult than most.
This is what the changer mechanism looks like with the top cover off. Rather than using platform gears and trays, this one uses a central hub with small metal platforms to hold the discs.
This is an up close look at the hub mechanism. You can disassemble it by removing the Philips #00 screw in the center, but be warned... that screw is ridiculously tight. I stripped out the head trying to remove it. In all likelihood, if your changer has eaten its discs, you may end up having to destroy those little metal platforms to get them out again, or break the black plastic keeper in the center.
Before we can get any discs removed the mechanism must be hand cycled so that the rollers in front and loading arms in back are out of the way. Turn the whole unit over, so that the circuit board is facing up.
See this white gear? Manually push it in the direction of the arrow, as far as it goes.
Presto, you now not only have access to your discs, but the platform hub has now run itself all the way up.
Note that if you plan to re-assemble, you must return the rollers and loading arms back to their original positions. Spin the loading gear I showed you away from the arrow in the preceding picture to do that.
I promised I would show you the two features that may fight you upon re-assembly, and here they are now. One’s a pin and one’s a hole for another pin. They won’t be very far out of position, just wiggle these parts around enough to get them to fit into place.
Be very careful with the rest of the gears on this top cover. They are well lubricated and will move out of position very easily. You don’t want that, because then the changer will be out of alignment. It is probably best to use a marker to indicate where they originally were, though the mechanism isn’t quite so freely lubricated as to give you instant nightmares if you don’t do it.
Before I leave you, I’ll show you the mainboard quick. It is possible to remove it from the bottom of the housing, but there is almost no reason to. 99% of it uses surface mount parts, which require more specialized gear than just a simple soldering iron. That said, there are some joints underneath that may do well to get touched up.
Release the twist tabs arrowed in blue. Make sure the two screws I showed you on the back panel have been removed. Then, remove the three red arrowed screws. Lift the board up and out.
This is the underside of the board. If there are any solder joints to touch up, they will be the ones indicated. On the bottom right are the solder joints for the two heatsinked transistors, while the top right has the joints for the eight pin main interface connector.
Are we done? Excellent. Put it all back together in reverse order. This isn’t a hard device to put back together, so you should have few problems. Consult my pictures as needed.
Eventually, I hope to show you the inner workings of the RBQ unit that uses this changer mechanism. Since I do not have one yet, though, I’ll be going back to the world of cassettes for my next article. Good luck, and I’ll see you then.
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