1999 Dodge Ram 1500 Premium Radio Choke Circuit

by Jeremy Schrag

1. 1999 Dodge Ram 1500 Sport

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This guide is for Chrysler/Infinity stereo systems from 1987 until roughly 1999, when they began to evolve into something more sophisticated, which I haven’t studied in depth yet.

Some Chrysler/Infinity speakers are shown above: from left to right, one 6x9” from a 1990 New Yorker, one 5.25” door speaker from a 1988 New Yorker, one 3.5” dashboard main speaker from a 1994 Concorde, a 5x7” rear speaker from an early Daytona, a 5.25” dash speaker from a 1989 Caravan, and finally a 5x7” door speaker from a 1992 Caravan.

Except for the Concorde’s dash speaker, all were built using polypropylene woofer cones; but some are more robust than others. The Daytona speaker and the one to the right use small woofer magnets in a doughnut shaped amp, making bass sound rather sloppy. These also have half-inch voice coils, where the larger magnet models typically used one-inch voice coils.

The onboard amplifiers all use NEC PC1230H2 amplifier chips, giving them 20W RMS of useable power. They also have various levels of attenuation and equalization built in, to tailor the sound to each car.

The Infinity RS system was used in the 1991 and later Imperial, New Yorker, and Dynasty; it used an enhanced speaker system with stronger bass output, concert-hall imaging, and smoother response. The system used ten speakers in six locations — woofers in the front doors, co-ax midrange and tweeters in the instrument panel, two-way speakers in the rear shelf panel, and a central 120 watt amplifier in the trunk.

A Word About Tweeters

The tweeters varied from excellent sound quality to mediocre. Here’s my order of preference:

1. EMIT (ElectroMagnetic Induction Tweeter). These were offered on only two vehicles to my knowledge: 1988-1989 minivans (dashboard), and early LeBaron convertibles (rear). The LeBaron models are quite beefy due to the need for more powerful bass, with larger woofer voice coils and magnets, and the tweeter itself isn't as attenuated as the minivans.
2. Soft dome tweeter. These tend to blow if you beat on them, but for the most part hold up well and sound good. They were the most common tweeters in these systems, and were often used in the dashboards with the amplified woofers down in the doors (like my 1988 New Yorker). Most rear speakers also had these tweeters.
3. Mylar cone tweeter. I don’t like these; sound quality is lackluster compared to the previous two entries, and they blow with appalling ease. Fortunately, they were only used for a year or two starting in 1990 as a bridge between the EMIT tweeter (which was likely too costly and/or quiet to use) and the smaller soft dome tweeters (which weren't around yet). They can most often be found in the doors of P body (Sundance, Shadow) cars and the dashboards of the minivans. In around 1993, fabric replaced the mylar and the tweeters were then used in the dashboards of LH body cars, where they still blow easily, but are also the easiest to repair.
4. Paper cone tweeter. Most commonly found in the back seats of third generation minivans and in the rear speakers of LH body cars, these tweeters just don't sound good to me. They don't, in my opinion, belong in an “upscale” factory audio system at all.

EMIT ribbon tweeter in its natural habitat. I have a rather sophisticated system for checking for these at the boneyards – I pop the dash grilles off the minivans, whichever side I can reach better, and feel for those four screws in a rectangular formation. When I find them, I giggle with glee and pull the speakers out to be added to my ever expanding collection.

Here's a soft dome tweeter in a 1993 Caravan dashboard speaker. These too are pretty easy to spot – just look at them in good light and see if you can spot that little white circle. If you see no white circle, but can still feel a round tweeter through the dust cloth, what you have there is a mylar cone tweeter.

General Speaker Notes

• If you're looking for bass, most Chrysler/Infinity 6x9s are capable of more of it than many similar-sized aftermarket speakers. The rear speakers from the minivans can be quite surprising, as the onboard amps are equalized and attenuated for the larger interiors in those vehicles. Remove the amps, and it is possible to get useable output below 30Hz. With the amps, they will give you significant output down to 32Hz or so but will be attenuated below that to prevent damage to the speaker.
• My collection's best sounding speakers – 1989 LeBaron Convertible rear speakers with EMIT tweeters.
• Most unreliable in the collection – 4 of my 5 LH body dash speakers needed blown tweeters repaired.
• Speaking of LH body dash speakers, they are able to drop into the dashboards of M body cars with very little modification. Just cut a small notch in the dash for the terminals, and they'll drop in and bolt up like they were made for the car.
• The most unreliable amps are any door speaker with an amplifier filled with potting compound.
• The most reliable Chrysler/Infinity speakers are any of the 6x9s. On rare occasions I'll find one with a blown woofer voice coil, but the amp has always turned out as good. The dome tweeters are usually a weak point, though. Second generation minivans seem to be best for having good tweeters.
• Can often present too much bass with the Chrysler CD/cassette combo deck for some people's tastes, due to the auto loudness circuit incorporated in those radios. Some other later model Mitsubishi made Chrysler head units, like the changer control cassette deck, have the same auto loudness circuit. To get around this in a factory CD deck, try the Infinity IV single CD deck with the supplier code 26777 (Alpine made). These use the same Toshiba 15W x2 RMS amp chips the combo decks do, but they don't have the aggressive loudness circuit.
• Certain early minivan 6x9” speakers were made with tweeter mounts too weak to handle liftgate slamming, resulting in breakage of the mount. There's a TSB (D-89-24) out there for that problem.
• LH body cars with the spatial imaging system use a third dashboard speaker in the center. It is little more than a paper cone full range speaker wired between the two positive leads of the main dashboard speakers.
• Some early cars also got rear headphone jacks when equipped with the Infinity systems. These not only cut off the audio to the rear speakers when used, they also cut off the power to the onboard amps on the rear speakers.
• Most cars using onboard amplified speakers were pre-wired for the Infinity systems at the factory, whether they got it or not. On Dynastys, for example, the relay location above the glove box was left open while the tweeter wires are taped to the dash harness. Amp relay ground wire is usually taped to the harness behind the radio. Dash tweeter locations were plugged by a black piece of cardboard with a foam backing. Door and rear speaker locations got the proper connectors with all four wires present – the non-Infinity speakers just used the center (speaker level) wires only. I have retrofitted Infinity into a 1988 New Yorker successfully – all I needed to do was put the relay in, connect the relay ground wire, and install the Infinity speakers. There is another component, a choke that often goes under the dash somewhere to filter interference from the amplifier power feed, but this does not need to be installed to get the system working. Some early Infinity speakers even had their own choke attached to the speaker basket.
• The relay used to power up the amps is shared with the power antenna (if equipped). It is often called the NBS (or name brand speaker) relay in factory literature. Its location varies depending on the vehicle.
• Rear speakers of LH body cars do not have a crossover for the tweeter – they depend on the amplifier module for this.

Wiring and connectors

Another common question I see in the forums is which wire does what on the amplified speakers. This is easy, as all of these speakers use the same pinout from a 1987 New Yorker to a 1996 Grand Caravan. Connectors on these are either a four pin square affair used in dashboards and rear speakers, or a smaller rounded weathertight connector used most often in doors. On each of these, one can easily determine what wire does what using the following color code on the speaker itself.

Red – amplifier 12V input
Green – speaker level audio input from head unit, positive
Black – speaker level audio input from head unit, negative
Gray – amplifier ground

On the co-axial models, a second set of green and black wires goes to one set of terminals, while a blue and white wire from the amp goes to another set. The green and black wire carries the speaker level signal to the tweeter, which has a crossover capacitor and attenuation resistor mounted underneath it, while the white and black wires are the connection from the amp's output to the woofer. The amplifier only contains crossover circuitry for the woofer – the tweeters are left to fend for themselves, in other words.

Some of you may be asking what the black box is on the bottom of your second generation minivan dash speakers. These are crossovers for the woofer on these (the tweeters again get their own, mounted to the tweeter itself), commonly called bass blockers, used to keep these speakers from playing notes the door speakers were put there for instead. These are a common failure point on these – I'll address them in the repair section.

Speaker/Amplifier Repairs

Buzzing and Rattling Noises

Some of these speakers over time tend to have the glue dry out on the plastic brackets used to hold the tweeters in place. I have had minivan 6x9s that have literally fallen apart on removal thanks to this. When this happens, carefully look at the woofer cone and tinsel leads (the wires that go to and through the woofer cone for the tweeter and woofer voice coil) to make sure no damage has taken place, glue any loose tinsel leads back down, and glue the bracket back down. Buzzing noises are also another symptom of amp issues. If the speaker is not literally falling apart, first check all the tinsel leads (sometimes they work their way loose) before suspecting the amp.

Heavy Distortion, Too Much Bass at Low Volumes, Static, Low or No Sound from Woofer

You likely have amp problems. However, 95% of the time this is a fixable problem. I find that all amp problems more or less come down to bad soldering joints in the amp itself, which as you know is bolted to the back of the speaker (or in a big black box if you have an LH or later AC body car). To repair these, you must first remove the cover, which is both clipped and glued down, gently pull out the amp, and use a low powered iron to re-solder all joints in the amp. Most of the time you'll find that upon putting the amp back together it now works properly. Don't worry about breaking the cover clips – my usual MO is to glue the cover back on when finished anyway.

1999 Dodge Ram 1500 Sport

But what if you have a door speaker with an amp full of potting compound that's acting up? Well, most of the time these are even more susceptible to bad solder joints than the non-potted models. The trick is to first get the cover off the amp (which is often easier said than done), then get the amp out of its enclosure, and then remove the potting compound from the underside of the amp circuit board so you can solder.

My usual plan of attack for these ornery door speakers involves a pair of small jeweler's screwdrivers to pry the cover off and amp out. The cover has four cylindrical holding tabs that go down through the potting compound to the PCB itself – these are often a bear to loosen up, and sometimes break. Once I have the amp out, I use my 60 watt soldering iron to melt straight through the potting compound (in a well ventilated area) and heat up some of the larger PCB traces on the amp. This often heats up the compound enough that you can get a small screwdriver underneath it and peel it off the underside of the amp. Be careful though, as this compound can get quite brittle at times – watch your fingers and take your time as you scrape that stuff off. Reheat the PCB traces as necessary. If you get real lucky, you'll be able to peel it off the entire underside in one go.

This is one repair where impatience can get you a nice screwdriver shaped gash in your thumb if you're not careful. When I do manage to get that stuff off, I switch to my 25 watt iron to do the re-soldering; as the potting compound from above the PCB tends to make the solder bubble as you work if you use too much heat. When finished the repair, I always place the amp back in the case and test them a while on the bench before gluing and/or melting (if the case has been damaged during removal) the cover back on.

I am pleased to report, however, that I have not yet had a potted amp that I couldn't fix just by re-soldering it. I've fixed ten AC body door speakers and two minivan door speakers this way.

Above, you can see two examples of Chrysler/Infinity onboard amps. The bottom one came from a 6x9” speaker with a blown woofer voice coil, while the top one is potted and came from a 5.25” door speaker. These are quite simple but reliable amplifiers, and are identical in circuit design. The large chip sticking up from the bottom of both amps is the power amp chip (the NEC PC1230H2 itself), and is the only part mounted to the speaker's heatsink. On the far right, you can see the preamp chip near the black and green audio input wires. When your speaker is giving you static or distortion, it is the preamp section that likely needs the soldering iron's touch. Often, the power amp chip will need it done too. On the left you can see the voltage regulation section – look here first if it's totally dead. But, you know what they say about an ounce of prevention – it is best to re-solder the whole amp while you have it apart because, at least in the case of the potted models, you're not going to want to take it apart ever again when you're done.

Blown Tweeters

This is going to be a short section, quite frankly, as I have had little luck fixing these. However, it is possible on the LH dash speakers, so I thought I should discuss it. The dome tweeters are very prone to blowing anywhere in the voice coil they can get away with it. The only time I've ever fixed a blown dome tweeter was when the break in the wire was near the edge of the diaphragm, and it only stayed working for fifteen minutes before it blew again. So, forget about the dome tweeters. Also, forget about the mylar tweeters – when these blow, they tend to melt the cone around the wire making it impossible to repair them.

Blown EMIT tweeter? Send me a picture, because I've never seen a dead Chrysler/Infinity EMIT, and I have five pairs of them.

The LH dash speakers are another matter. After buying four of them with blown tweeters, I was able to repair all four. This is because they tend to blow at the tweeter terminals, and one can solder in a small piece of wire to repair them. Getting to those terminals is not easy, however. First, you have to disconnect the speaker from the wiring harness, which often results in the speaker's main terminals being damaged due to absurdly tight connectors. Then, you have to very carefully use a razor knife and jeweler's screwdrivers to pry up the tweeter ring. Only then can you access the tweeter terminals. Some pictures are in order here.

Here you can see the tweeter ring removed with the terminals exposed. As you can see from the thicker wire, I was running a signal to the tweeter terminals at the time to determine where the break in the voice coil wire was, and where to solder .

This is about as close a shot as I can take, and yet you still can't make out the voice coil wires too well – they are that small. The thick silver colored “wires” you see in the picture soldered to the terminals are actually small lengths of capacitor lead. When soldered to the terminals, these are easy to bend in a direction where you can more easily solder the voice coil wires to them.

How does one find the voice coil wires? With great difficulty. They are glued down into a small trough on a slope that starts at the terminals and disappear into slits in the black plastic about as far up as my capacitor lead segments go in the above picture. I use a pin or sewing needle to carefully dig into the glue and pry out the coil wire, which is so small you need very good light and good eyesight to even see it. It's about the size of a human hair. Fortunately, because they are so small, you can pre-tin your capacitor lead segments and a mere touch with a low powered soldering iron to the coil wire will solder it right up. So far, though it is a job and a half to do it, I have a 100% success rate in fixing these tweeters.

With all this being said, the most common place those voice coil wires break is right at the tweeter terminal. With luck, you won't have to do much digging to get at them.

Intermittent Minivan Dashboard Speakers

A few times, I've seen complaints among owners of second and third generation Chrysler minivans that the dash speakers were going on strike. Then, when the radio was turned up, the dash speakers would suddenly pop in and work. The problem here isn't the speaker itself, but the woofer crossover (bass blocker) on the back. These just love to go all flaky at times for some reason. The solution is to bypass the bass blocker. I like to connect jumper wires between the tweeter terminals and woofer terminals to do the bypass, as the tweeter terminals get a full range signal (their crossover is attached to the tweeter itself).

Here's a bad picture of one of my 1991 minivan dash speakers with mylar tweeters. Just cut the blue and white wires, connect jumper wires between blue and green, and black and white, and you're good to go. If that doesn't do the trick, cut the red and black wires where they go into the bass blocker at the main connector, remove the main connector from its holding tab, and solder these wires to the tweeter terminals too – red to green, black to black. A side effect of this operation is that these speakers will now be trying to help the door speakers with the bass, but I find these to be rather capable little speakers. They can take it.

Co-axial Dome Tweeter Replacement

I mentioned that I've had mixed success in finding the 6x9” co-axial Chrysler/Infinity speakers with working dome tweeters. Often, what I will do is look for working dashboard tweeters from an early AC or J body car (use a multimeter at the yard to check for continuity across the tweeter voice coil), and then use that tweeter to fix the co-axial speaker. This, however, is not too small a job. First, one has to remove the dash tweeter and attached PCB from its mounting plate (there are three screws up top holding it on), leaving the capacitor and resistor there (use the one from the co-axial). Then, I carefully peel back the dust cloth on the co-axial until I can see the tweeter and de-solder the tweeter tinsel leads (they'll be on the side of the speaker with the black and green wired terminals).

Once the tinsel leads are de-soldered, I then carefully pry up and remove the plastic tweeter bracket, replace the tweeter using the existing crossover capacitor and resistor, glue the bracket down again, re-solder the tweeter tinsel leads back in place, and finally glue the dust cloth back down. I've successfully repaired two 6x9” co-axials this way.