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The Chrysler RBU Stereo-CD Stereo Head Unit From Alpine: Takeapart Guide

by Jeremy Schrag

In my last article, I mentioned that Chrysler, at the start of the new millennium, wanted to give us consumers a lot more options when it came to entertainment in our vehicles. In vehicle DVD players weren't that common yet, however, and yet people still asked for ways to keep the kids in back entertained on long trips without bothering Mom and Dad in the front seats.

A compromise was reached around the year 2002, when Alpine Electronics came up with a special version of the CD/cassette combo deck with the sales code "RBU." Today, I'm looking at this exact head unit. Featuring rear seat audio capabilities, this deck was often found in Chrysler minivans that did not have DVD players. As such, it wasn't that common a deck to find.

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Pictured above, we find the sales code for this deck in the exact same place we found it on the RAZ, a very similar looking deck. Indeed, most of the functions of this deck parallel that one, with only the rear seat audio function being different. This unit does provide CD changer control, RDS, and satellite radio functionality, just like that one.

Sharp eyes will have spotted a round black circle on the right side of the picture above the scan button. This is the infra-red sensor for the rear seat audio remote control, a very useful but not totally necessary component of this feature. Rear seat audio can be controlled by both the remote and the front panel controls, via the "rear" button you see in the picture. More on that later.

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Here's the top panel of my RBU sample deck. As you can see, the supplier code is 26777D, indicating Alpine as the OEM.

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On the bottom, we find something we've never seen before on a Chrysler head unit - an FCC compliance sticker. This is because this deck actually has a radio transmitter inside it, used to broadcast the rear seat audio signal to the wireless headphones that are an essential part of the system.

Now, while I was researching this deck, I hunted high and low through the jungles of Google for the manual so I could find out how the rear seat functions work. Thanks to this label, I learned that finding the manual is actually quite easy, once you explore the database of the FCC itself. See that FCC ID number? Well, if you take that number and go over to the FCC website and plug it into their database search, you will find that the owner's manual for this deck is stored on the FCC servers, free to download for anybody who wants it. The other data found there again confirms Alpine as the OEM.

This method of finding the owner's manual won't work for most other Chrysler decks, however, because most others don't have radio transmitters in them. As such, the FCC doesn't need to specially certify them.

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Here's the left side panel for the deck, all one big heatsink for the amplifier and voltage regulator sections of the deck. All screws are Philips #1, for future reference.

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The right side of the deck consists of the tuner module, just as in the Mitsubishi built RAZ deck I looked at.

Now that we've looked at the outside, let's get inside. I'll start by removing the EQ slider knobs, volume knob, and balance and fader knobs. Then, I'll remove the two screws holding on each side of the faceplate and pull the faceplate off.

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As you can see, this unit is not built the same way as the RAZ was. The PCB for the faceplate stays behind on this deck, whereas it was bolted to the faceplate in the RAZ.

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Once again, microlamps are used to illuminate this deck, and once again they are surface mount devices soldered down to the circuit board. These are quite a pain to replace, even for experienced technicians.

Removing this circuit board to facilitate disassembling the rest of the deck is almost as much of a pain. In the picture above, you see three red arrows. These point to three twist clamps that hold the board to the deck. These must first be de-soldered, and then you can twist them to release the board. After that, the board carefully pulls straight off, joined to the rest of the circuitry by two connectors and a co-axial antenna wire that's plugged into the back. Why is there an antenna wire? Well, see that blue circle above? That's the transmitting antenna for the rear seat audio, right there. It's a little thing, isn't it?

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Near the upper right corner of this shot, you can see the antenna connector. This is a miniature barrel connector that just pulls straight off.

Now, I'll remove the CD module so I can show you the pertinent details of cleaning the laser lens and adjusting the laser power, if needed.

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Four red arrows indicate the mounting screws for the CD module. Two of them are on the back panel of the unit, two are accessed through the holes indicated near the bottom of the picture. The module then lifts straight up and out.

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This deck is absurdly easy to clean the laser lens on. Why, you can even do it without removing the CD module at all. Above, you can see how the loading mechanism leaves a big slot in the top of the module. The laser lens can be access through here. Just pass a Q-Tip moistened with alcohol through there, and gently clean the lens. This might just fix your CD error issues right there, without having to get any deeper into it. But in case it doesn't, let me show you how to get at the laser sled to adjust the power.

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Here is the underside of the CD module. In the bottom left corner, you can see the connector that joins the module to the mainboard of the deck. This entire circuit board needs to come off to get at the laser power potentiometer.

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First, remove the screw indicated by the green arrow. This will release the board so it can be removed. Note the presence of the metal catch by the lower red arrow... the board slides upwards for release.

But before we release the board, we have two ribbon cables to disconnect. Indicated by the red arrows, these are disconnected by releasing the connector catches on each side and then sliding them out of the connectors.

The upper ribbon cable has something a mite more devious in store for us, though. It is actually soldered in place, where the yellow arrows are pointing. These must be de-soldered before the circuit board will come off. Simply touching your iron long enough to melt the solder while lifting gently on the cable should be enough to free it. Similarly, a quick touch with the iron should solder it back into place when you're done.

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With the board gone, we can now get at the laser power adjustment, circled in yellow. As this is a sensitive adjustment, don't tweak it too far in one direction without re-assembling and testing. It doesn't take a lot to make a big difference in how well the unit reads certain discs.

Perhaps you need to replace the belt in the tape deck though. This requires, like the RAZ, taking the rest of the deck apart.

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Remove the screws from both side panels, and remove the big black heatsink from the left side. You should then see the above image. Before we can get the mainboard out, we need to release four twist tabs, indicated by the red arrows. And lucky us, they are soldered down. I do not envy you here, for these take a steady hand to de-solder and are quite a bit trickier to release than those we saw on the front panel PCB.

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Before the mainboard will come out, two modules need to be removed. The tuner module, seen above, has but one screw holding it on. Just pull it straight off - not much about this deck is easier.

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When the tuner comes off, you can see the cassette module hiding underneath the mainboard.

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Now, we need to remove the amplifier/voltage regulator module on the left side of the unit. With the big black heatsink removed, all you need to do here is remove one solitary screw on the back by the connectors. This module will then pull out, easy as you please.

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The other side of the amp module. Believe it or not, this unit uses the same power amplifier chip as the RAZ.

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Now that both side modules are out, we are almost ready to remove the mainboard. Before we can do that, we need to sort out that gray antenna wire that goes to the front panel PCB. Just make sure it's not going to get caught on the metal of the front panel when you gently pull out the mainboard.

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A quick look at the front panel before we pull out the mainboard. While you could remove the volume, balance, and fader control circuitry as well, there really is no need to.

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As you can see, the mainboard has been removed. You can see the big metal module at the back towering above the board - this is the RF transmitter for the rear audio headphones.

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If you thought dealing with the mainboard was hard, it's now time to mess around with the tape deck. This mechanism is quite a bit more complex than that found in the RAZ. To begin, remove the screws indicated by the blue arrows and pull the module up and out.

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This deck hides the tape belt inside a metal shield, which also holds various loading mechanism gears in place. Degree of difficulty is about to go from an 8 to a 20. Remove the four blue arrowed screws.

See that area circled in red? Pay special attention to the wires, there. When you reassemble the deck, leave those wires exactly as you found them. We don't want them pinched when the shield goes back on.

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This, as they say, is the hard part. You will not get the metal shield all the way off without de-soldering the ribbon cable for the reel sensors, which I did not do. The tape belt can be replaced without messing around with that. Just lift it up high enough to get in there and replace the belt.

And boy oh boy does the deck have a nightmare for you... now you have to put that shield back exactly as it was.

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And to do that, you need to line up the loading gears. See the gear arrowed in yellow? It has to mesh perfectly with the teeth on the sliding mechanism also indicated in yellow. Not only that, the rest of the gears need to line up with the gears below. This may take several attempts with a small slotted jeweler's screwdriver to do. The key is to bring a great deal of patience to the table the day you do this. I managed it just fine, but this is not a job for the faint of heart or those working on electronics for the first time. This part of the job was incredibly aggravating, let me tell you.

And don't forget to make sure those wires for the loading motor aren't pinched.

Now, re-assemble the deck. I hope you remember how things came apart!

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Before I go, here are some shots with the unit operating.

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To use the rear audio function, you can activate it in one of two ways - the front panel and the remote, assuming you have the remote.

To turn it on via the front panel, first select your desired operating mode for the front speakers. Then, hit the "rear" button. A headphone icon will flash in the display. While it is flashing, select the desired operating mode for the rear headphones. The rear speakers will automatically cut out. Volume is controlled directly on the rear headphones themselves - no need to worry about that. The headphone icon will show in the display as long as the feature is in use.

Setting it up via the remote isn't hard either. Hit "power" on the remote to enable the rear audio, then hit "mode." One press of the mode button just shows you what mode the rear audio is on currently. Press it two or more times to cycle between CD, tape, changer, or what have you.

Getting interference on the headphones? You may need to go to an alternate transmitting channel. To do that via the front panel, press and hold the "rear" button for about two seconds. The display will show what channel it's on. The remote has a "channel" button to access this same functionality.

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RDS (radio data system) functions are identical to the RAZ unit I looked at before. FM mode only, of course. When present, the transmitted data cycles through the display where it says "Adlt Hit" in the above picture.

To seek or scan for RDS stations, hit the "PTY" button once and then seek or scan. Hit that button more than once, and then seek or scan, to go looking for specific genres.

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One last paragraph before I call this an article. You can indeed check the vehicle's Sirius ID number if so equipped with this head unit, just as you can with the RAZ deck. It is done in the very same way - turn the deck off, and with the key in the accessory position; hold the time and CD eject buttons simultaneously until the data comes up in the display. Then, you can call in and get the satellite radio stuff activated.

Missing the headphones for rear seat audio? Seek out part number 05082012AD or 4685923AA for the full headphone kit, or part number 04685936AD for individual headphones. These will cost you, but they are currently available at places around the Internet.

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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