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Working on the Chrysler RES stereos

by Jeremy Schrag

Technology certainly has come a long way since I was a kid growing up in the 1980s. Back then, when you bought a new vehicle, you were lucky if an AM/FM radio came as standard equipment. Cassette decks were available, but they were often expensive. Some early Chrysler vehicles even added an optional rear speaker amplifier, with more powerful co-axial speakers. CD players? Forget about it... you needed to wait for the mid-1980s to roll around first before Chrysler began to offer these on new cars, and even then they were available on certain models only and required a wallet full of hundred dollar bills to buy. [Editor's note: CD players were first launched in 1982; the first car CD player was launched by Pioneer in October 1984.]

Jumping forward to 2010, consumers are more demanding than ever. Not only is a new vehicle expected to come with a once expensive CD player option, it's considered a much desired feature that support for various external devices be added as well. Today, I'm looking at the Chrysler RES head unit, which came standard with many 2010 vehicles. This is currently just about the most basic head unit you can get on a new Chrysler vehicle, and we're going to have a look at the insides to see what's in there.

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Some of my readers may be asking what I'm talking about when I say "RES." Well, these three letters are a sales code identifying the particular head unit in question. Chrysler has been using these codes since the 80s, but until recently they haven't had much public exposure. These days, most Chrysler head units display this sales code right on the faceplate, as you can see in this picture.

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There are two versions of the RES. One of them is the basic stripped down version we are looking at here today, fresh out of the dashboard of a Challenger, and the other carries with it a few more features like Uconnect and satellite radio support.

Among the features of this version of the RES are MP3 playback support via the CD player and a front panel auxiliary jack for your iPod or portable DVD player, both welcome features for yours truly. The geek in me would like USB support as well, for MP3 files stored on a USB flash drive or portable hard drive, but Chrysler is off to an an excellent start with this unit. We can't expect things from this deck that would come with a more expensive option, like the MyGIG decks. Extra features add extra cost.

At this time, I must apologize - I am not able to get into any detail on how this deck works. Sometime during the early part of the new century, Chrysler came to a decision that I find rather unfortunate: the company began to make all their head units dependent on the vehicle's computer bus. Without the presence of the other vehicle computers, the audio system would not function. Premium amplifiers were now switched on through the bus by the vehicle computers, and stock head units would not turn on unless they could talk to the other computers in the vehicle. This head unit is no exception to this new rule.

But wait, it gets even more complicated. Due to changes in recent years to the computer bus, you will often find that some newer head units will not work properly on vehicle models of a different year, even if they physically interchange. And it doesn't even stop there - some vehicles had a high speed computer bus, while others had low speed depending on how they were optioned out. My latest information is that you cannot even interchange high speed bus compatible decks with the low speed models.

Is all this rather confusing to the customer? You bet. I'm confused, and I've been an electronics technician for decades. My advice to you, if you find yourself bushwhacking through eBay looking for a replacement for a dead head unit, is to choose carefully. After 2006 or so, try to find something out of the same model year for best chance of success. Anything else is a gamble. Some may even require a trip to the dealership for a visit with their scan tool so that your Sirius satellite subscription is carried over, among other things.

You may be asking yourself what your options are if you want a non-bus-dependent deck for your vehicle. Well, the last head unit that I know of to not require the computer bus interface to operate is the RAQ. This is a 6 disc changer model built by Alpine that also plays MP3s. This head unit is in high demand, however, so be prepared to pay for it.

Let's come back to the RES we're looking at today. Because I am not able to power it up, I'm going to do something else I like to do to things that won't work for me - I'm going to take it apart and show you the insides.

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Our first stop on the tour of the RES is this shot of the side panel. You may be thinking to yourself that it looks like there is a place to mount a small cooling fan, and you'd be right. It is likely that this same housing is used across many models of decks.

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This is the back panel of the unit. In the lower left we see Chrysler's newer style antenna connector, which I must admit makes for a more secure connection than the Motorola barrel connector used throughout the 70s, 80s, and 90s. Next to this connector are the three connectors that join the head unit to the vehicle wiring harness. Sharp eyes will have spotted that the gray connector on the left has no pins in it. This connector is for all the optional stuff, like DVD players. The fact that we see no pins here means that Chrysler likely doesn't intend this particular deck to be used with the optional goodies, but we should still be able to interface with any premium amplifiers in the system. This is because despite all the technological advancements made, Chrysler is still using the speaker level outputs of these decks to provide signals to the premium amps rather than line level outputs. This is not a bad thing - it increases the chance of compatibility if, say, your regular deck is out for repairs and the dealer has to give you a loaner to get you by for a while.

Some of you may be wondering what the two gray connectors do that still have the pins in them. Well, the big one on the right is the important one. That's the one that has all the speaker outputs, power connections, and computer bus connections. The little gray one in the middle is for hands free phone stuff, according to the meager wiring diagrams I was able to get a hold of. It is not clear to me at this time that this unit is able to actually do anything with that connector, as this is the RES model without all the Uconnect gadgetry, but there may be some functionality still present.

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Moving on, this side of the head unit features nothing more than plain old sturdy metal housing with lots of ventilation holes for the parts inside.

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The supplier code for this deck is 53956, which is a clue to who made the unit. Unfortunately, this is a code I've never seen before, so I'll have to take a stab in the dark and guess who made it. I may be wrong, but the most likely prospect for this unit is that it was made by Siemens, who bought out Chrysler's Huntsville Electronics division a number of years back.

Let's open up the unit now. To do this, you need to remove two Torx T-15 screws on either side of the unit located at the rear of the unit. You can see them in my pictures, colored gold. Once this is done, you can pry the top and bottom covers off the unit at the back. Be very careful doing so - these covers are very firmly snapped down to the rest of the housing. Additionally, the bottom cover is attached to the main circuit board by thermal pads... these will want to try to pull the circuit board out with them, and you'll have to hold the board in place as you carefully pry the cover off. I'll show you what I mean a bit later on.

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This is what you see once the cover comes off - the top of the CD player module. The red arrows point to two of the four mounting screws that hold the module in... these are Torx T-10 screws.

Near the bottom of the picture, we see the three plastic clips along the top that hold the faceplate on. We need to remove the faceplate to access the two remaining screws for the CD assembly. To do this, very carefully pry those plastic clips up and over the metal tabs. There will be clips like this on the bottom of the faceplate as well. I find it best to start at one side and work my way towards the other.

Let's take a look at the faceplate for a moment.

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This is the view you get once the faceplate comes off. You can see the long CD loading slot up top and the rectangular black connector that joins the faceplate PCB with the rest of the deck. What I'm going to do now is show you how to take this apart, just in case someone shook a bottle of soda and then sprayed it directly at your radio, making all the buttons gum up.

First, remove the two big knobs on the front. They are just pressed on, so you can pull them straight off. Then, you need to remove a few screws. As you can see in the picture, there are eight Torx T-10 screws holding the PCB in. Once you remove those, you can lift the board right out of there.

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As this picture shows, every single button in the unit uses one gigantic membrane contact assembly to make contact. You can now remove the whole membrane for cleaning - I recommend a soap and water solution. Make sure it's dry before you put things back together.

On the circuit board side of things, you can see where all the contacts are and clean them too, as needed. Fortunately, the membrane itself should protect the circuit board from your soda blast just because of the fact that it takes up most of the space behind the buttons.

Some of you may be wondering about changing illumination light bulbs while you're in there. Well, that's not going to be easy, if you're unlucky enough to be having problems there. Along with all the other technological advancements we've had recently, this unit doesn't use light bulbs - it uses surface mount LEDs, or light emitting diodes. Replacing them should normally not be necessary. To do it on this deck, one needs to be proficient at soldering surface mount devices. Even I, an experienced tech, find this a chore thanks to my gigantic hands.

Some of you may have spotted something interesting - the contact membrane has more contacts than the faceplate has buttons. This was likely done so that the same membrane could be used for multiple head units. Smart idea, if you're a bean counter. And if you look really close, you'll see that the circuit board also has contacts for buttons that aren't there, likely for the same reason. There are even spaces for extra illumination LEDs.

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Now that the faceplate is out of the way, we can finish taking out the CD assembly. The red arrows point to the remaining mounting screws.

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The CD assembly is wired to the main circuit board through this ribbon cable and connector. It is very easy to detach - just press the little tab you can see on the lower edge of the connector and pull the connector upwards.

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Before we go any further into the disassembly, let's stop for a moment. Some of you may be dealing with CD players that no longer are able to read discs. Common practice is to clean the laser lens first to make sure that isn't the issue. On this particular deck, this isn't exactly an easy job. The laser lens is difficult to get at, with a lot of metal blocking the view. In this picture, we are looking at the side of the CD assembly with the gray ribbon cable on it that connects to the rest of the deck.

The hole in the center of the picture offers the only easy access to the laser lens I have found on this deck. I was not able to get a clear picture of the lens within, but you should be able to see it in good light through this hole. It looks like a clear plastic bubble on top of the laser sled. Moisten a cotton swab with some isopropyl alcohol, and then gently reach it through the hole to lightly brush the laser lens. Just a quick swipe should do the trick. Then, reassemble the unit far enough so you can test it. If it still doesn't work, now you can move on to the more invasive stuff like adjusting the laser power level.

Speaking of the laser power adjustment, I'll show you where it is.

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Here we see the bottom of the CD assembly. Though it is not too likely that you will be able to restore this particular CD assembly to working order should a laser lens cleaning not help you, I'll show you how to get into it far enough to adjust the laser power, as I did on my older articles.

First things first - see those little round holes in the PCB? Those are there to help us disconnect the laser sled ribbon cable, and it must be disconnected to access the laser power adjustment. You can use something like a toothpick (or in my case, a dental pick) to reach through those holes and unlatch the connector. I'll show you the connector from the other side in the next picture so you can see how it works. But before I do that, we have some screws to remove and some wires to disconnect.

The screws themselves are easy. They require a Philips #00 screwdriver to remove - these are usually found in jeweller's screwdriver kits. The wires, however, will require de-soldering. I'm not talking about the wires you see in the picture by the black plastic piece - you can leave those alone. No, the wires we need to de-solder are hidden beneath that black felt tape you see in the top left corner of the picture. Carefully remove the tape from the PCB. There will be two wires soldered to the board underneath. After you make note of which of the two wires go to what solder pad, touch your iron to the solder joint and remove the wires. It only takes a second. Now, all that's holding the board down is the laser sled ribbon cable. Once this is out of the way, the PCB can be flipped up and over and then set down on the black plastic piece seen above.

Gently pull up the outer edge of the PCB, the side with the gray ribbon cable on it. You will need to pull it down slightly, as it has tabs that lock into the metal up top by the upper screw.

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The red circle shows you the laser sled connector. To disengage the connector, slide the black plastic catch toward the ribbon cable but don't fully remove it. Use the holes in the PCB to pry against if it helps. The black catch will move forward about a millimeter or so, and will now allow you to yank the orange ribbon cable out of the connector. To reinstall, just slide the cable back into the connector and then push the black catch back into place.

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This is the laser power adjustment on the laser sled. If do you tinker with this to fix read errors, adjust in very small increments, put it all back together, and see if it's now working again. If you cannot get it to read discs again, there may be a problem with the laser itself.

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Replacing the PCB is a little tricky, once you're done with the laser sled. The circled white lever must be gently pushed inward, in the direction of the arrow, as you fit the PCB back into place. This is because there is a micro switch just below that square hole in the PCB. Normally, the white lever presses on a spring loaded plunger on the switch. But, once you remove the board that plunger will no longer allow the board to just drop back in place. We need to either move the lever just far enough to clear the plunger, as indicated, or depress the plunger through the square hole to allow the board to go back on properly. Not doing so will cause problems with the disc loading mechanism, not to mention keep you from screwing the PCB back down.

Once the board is back in place, resolder the two disconnected wires down and replace the felt tape. We're done with this part. Let's move on to the main PCB itself.

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Before I show you the main PCB, this is the bottom cover. As I mentioned earlier, this cover will try to bring the main PCB with it when you pry it off. You can see why in this picture - those two black block looking things are thermally conductive pads. They stick to the bottom cover and the underside of the main PCB, and are located directly under the main amplifier chip and the voltage regulator chip. This allows the bottom cover to help cool these devices.

Again, be very careful removing this cover. Hold the PCB in place as you pry the cover off slowly. We do not want to damage anything attached to the main PCB. The thermal pads aren't superglued down, but they stick well enough to flex the main PCB if you don't hold it in place.

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Once the bottom cover is off, the main PCB comes off after removing a few more screws. As you can see, most of the circuitry is made up of surface mount devices - almost impossible to repair should it ever need to be, unless you are a very experienced technician. The chip in the upper left corner is the voltage regulator module, a TDA3683SDC part. This provides all the voltages the deck requires for operation.

On the bottom right is the amplifier IC, a TDA7563AH. This is a fairly advanced device, featuring two ohm stability on all channels, full short protection on all outputs, and is able to provide diagnostic information to the rest of the deck. Rated power is 28 watts into all four channels at four ohms with 14.4 volts in.

And so we've come to the end of our look at the more basic of the two Chrysler RES head units. I hope I remember where I left all the screws.

General Chrysler-related radio and stereo articles at Allpar:
CD and DVD systems (stereos have a three-letter code on the face plate)
Tape and tape/CD systems
From here to Infinity
CD changers
Classic systems (before tape decks)

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