# The RMT-200 Tear-Down and Modding Thread [40+ Pictures]



## bmwman91 (Jul 28, 2015)

This little project of mine started last year, and on a BMW E30 forum as well. A number of members there are also VW fans and they told me that the folks over here would get a kick out of this, so I figured that I would sign up and share my findings and such. Apparently the RMT-200 is sort of hard to find now that it is out of production...and the fact that BMW E30 and E34 enthusiasts are also after them probably isn't making them any easier to find. I am sure that everyone on here understands the appeal of a fully-featured head unit that looks OEM since most of the aftermarket stuff looks like alien spaceships. The RMT-200 is widely appealing for that reason, and as I will later show in this thread, it is pretty trivial to swap the faceplate LEDs out for orange ones so that this unit matches the BMW interior lighting. Anyway, forgive me for being an E30 enthusiast posting on a Dub forum...but I am pretty sure that the actual content of my posts will provide good times for all.

This starts sort of slow, but just keep scrolling...I probably took this further than you'd think.

The project's goals are the following:
- Get switched 12V output for a power antenna and amplifier turn-on purposes
- Orange faceplate backlighting to match the E30 interior (blasphemy!)
- Quality 4V pre-amp outputs pulled directly from the DSP chip's DAC outputs, removing the big power amp from the signal path
- Enable the rear AUX2 analog input so I don't have RCA cables plugging into my dash
- Enable the rear USB connections so I don't have USB-anything in my dash

So, I got the unit and gave it a once-over. Looks like an OEM single DIN unit to me.

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Nice and OEM looking. With a pile of features. No wonder this thing sold out so fast.

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Model information. This unit is manufactured by Clarion's OEM division as far as I can tell based on the manufacturer's PN.

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Time to start tearing into this baby. Tamper labels...where we're going we won't need tamper labels. But, just to prove how easy these are to bypass, some careful prying and a heat gun set to ~75 Celsius has it off momentarily.

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Besides the label, there are a few screws and the black felt strip (with adhesive backing) securing the top cover. Once it is off you get access to the CD transport.

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The CD transport lifts out pretty easily. Tip the front edge (faceplate side) up and slide it over the metal tabs in the rear of the chassis. The flex cable is easy to detach from the mainboard...just reach under the transport and pop the black latch out.

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OK, so now we can see the mainboard. What are the main goodies on there?

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This NXP chip is the main signal processing unit. It takes the various analog and digital audio streams and handles volume, balance, fade and EQ functions. There are 4 DAC outputs that run to the big amp IC in the rear of the unit (pictured later). I contacted NXP to try to get a datasheet for this, but it apparently requires me to be a certified customer and sign an NDA. Luckily, I have a full board schematic for a JVC head unit that uses the same chip, so I had plenty of info to go on for the mods I cooked up later.

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This IC handles Bluetooth, SD card and USB inputs as far as I am able to tell. The product brochure for it indicates that it has all sorts of entertainment system capabilities, but like the NXP chip I can't get the datasheet.

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SDRAM and Flash memory for the Telechips IC.

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Time to flip this over and get at the bottom. Remove the 4 screws and detach the felt strip to get the bottom cover off.

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How kind of them to perfectly label all of the connections on the main amp IC and the connector output board!

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Time to get the board free of the chassis. Just remove the leftmost and rightmost screws from the rear.

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Now just tilt the big heat sink backwards to disengage the locating pins and push down to separate the mainboard.

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The mainboard also engages the faceplate with these 2 connectors. Just keep pulling backwards once the board is free of the chassis prongs and such.

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So, with the mainboard out it is time to get a look at the big amp IC that makes the rear heat sink get pretty hot at all times.

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Not only are there some screws holding this metal bracket onto the IC, but it is also soldered into the mainboard at the sides.

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Not that the solder is an issue. Get out your soldering iron and desoldering tools. It'll be out of the way in no time. We can now get a look at the big heat-maker. It is an ST Micro TDF8555J. The full datasheet is in the link below, for those that are interested. Note that this chip is not only the power amplifier for the speaker outputs, but it also has many linear voltage regulators onboard and it is basically also regulating all of the board's voltage rails. No wonder it gets so hot!
http://www.nxp.com/documents/data_sheet/TDF8555J.pdf

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Anyway, on to the front faceplate. This is of interest to me since I want to swap in orange LEDs (605nm) so it will match the E30 interior lighting. That's probably some sort of blasphemy in here, but it is what it is lol. This is much easier with the mainboard out. Either way, all you need to do is pop the 6 perimeter clips off of the tabs on the chassis.

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The board is easy to detach from the assembly. Take the screws out and free the end of the flex cable.

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Also remove the volume knob. It takes a heck of a pull to get it off of the quadrature dial.

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It is actually pretty easy to completely disassemble the entire faceplate, which is good since I am considering painting it matte black to better match the E30 dashboard. More blasphemy, I know.

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As for the PCB, just pop the rubber bits out and it's all yours for LED modding. Note that removing the LCD module requires a little desoldering as well. The metal frame around the LCD module is soldered onto the PCB in 4 places, so you need to undo that and bend the tabs a little to pop it off. You have to do that to get at the LCD backlighting LEDs.

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Also, the connector pins on the faceplate PCB are nicely labeled. I don't have any plans for this, but it's here for reference.

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LED mods done. Mmmmm. E30-licious.

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As far as integrating this thing into the car, the rear connections would need to be available. The SAFE connection needed to be jumped, so initially I just stuffed a scrap of wire in there to make the connection.

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But, that was hokey so I just jumped the pins on the mainboard with some 30GA wire. The E30 has no SAFE system in it, so there's no point in enabling that functionality. And YES, if you are thinking that the pads look torn-up, you are right. I actually removed the entire connector sub-board to check some stuff and things got a little messed up. Thankfully everything works fine so it's just cosmetic.

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Here are the nicely labeled pins for the output connector board (mini ISO on top, quadlock below). The keen observer will notice that some are labeled as being AUX inputs and USB...you don't say. Well, I have plans for those lonely, unused pins.

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*MAY BE OF DIRECT INTEREST TO DUB OWNERS!*
What WAS I doing back there? I was installing a ferrite chip in the empty spot for HB502. Doing this enables the switched 12V output on the rear ISO connector. This is sort of important if you have a power antenna or external amplifiers that need a switched 12V signal. This little chip is available on Digikey for $0.11 and is PN 445-1557-1-ND.

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*OK, this is all good and well, but that's all strictly amateur-hour stuff. Let's have some REAL fun!*



Remember my list of goals at the top of the thread? Well it is time to go after the last 3. Enabling the additional rear connections was fairly simple since it just required me to get some TE Micro Timer II terminals from Mouser. I'll post photos of the results a little later. They contain "spoilers" though, so I'll get to the REAL fun first...hi-fi pre-amp outputs.

So, as almost anyone that has dealt with car audio knows, tapping into speaker-level outputs to feed an amplifier's input often sucks and introduces unwanted distortion and noise. This unit leaves you with no choice though...no pre-amp outputs to be found here. Well, to hell with that I say. I see you there, DAC outputs. That's right, I am looking at you, HB202, HB203, HB204 and HB205 (the top 2 and bottom 2 gray things in the column of 6 gray things). Based on the JVC schematic I acquired, again which uses the same DSP chip, I knew that these ferrites were RF suppressors on the outputs of the DSP's DAC channels. That is the cleanest pre-amp signal you are going to get access to in here (not THE cleanest in an absolute sense, but the best you can get in this unit).

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So, just get some RCA cables, cut an end off and solder them straight in, right? WRONG. First, that would be a recipe for destroying the DSP chip's DAC outputs with ESD (electrostatic discharge). Second, the DSP chip runs on a 3.3V supply, and the maximum output voltage swing of the DAC is about 3V (2.1V-RMS) which I verified with an oscilloscope.

That is weak sauce, and a 4V-RMS pre-amp signal sounds a lot better to me (5.7V peak-peak) both figuratively and literally. But bmwman91, how are you going to do that? My first thought was to dribble some Four Loko onto the chip and hope for the best, but if that stuff isn't fit for humans then it probably isn't fit for electronics either. So, plan B was launched.

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Yes, plan B was some impressionist art. I call this one "Map Of Subway In The Mind's Eye". And yes, I cracked a beer open about 5 minutes ago while typing this...I am retyping 9 months' worth of posts down into one monster post for everyone's enjoyment here. No copypasta here, it's all fresh since copypasta is lame. Anyway, I'll leave the humor to the professionals and get back to the modding coverage.

I ordered up some prototypes of my pre-amp board design. The price difference between 2 and 25 was like $10, so I figured I might as well get some spares in case I goofed up or needed to level a table or something. Not quite big enough for beer coasters, sadly.

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Test-fitting them. They fit perfectly!

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Here's my little home electronics lab where I assembled my board and modded the RMT-200.

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Here's the result. The big beige things are relays. Finding small enough ones so that this would clear the CD transport was a bit of a challenge. Why relays? To protect the electronics from ESD when I am plugging audio plugs in, and to eliminate pops/clicks/noises as this board powers on/off. Basically, they act as output muting switches which ground the final output stage on the board. The relays keep the outputs of my board grounded for 2 seconds after the unit is powered on, and they ground the outputs ~40 milliseconds before the unit's main power rail goes down. Why? As power is applied and removed from the opamps on my board, they will make silly noises (pops/clicks/thumps) and I don't want that getting to my amplifiers. With this setup, I don't hear a single noise as power is applied and removed!

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Here it is installed (without the wiring harnesses connecting it to the DSP outputs and power). Nice fit! Plenty of clearance to the CD transport too.

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The opamps I chose, TI model OPA1654, are well regarded in the audio world. They perform very very well while not getting into esoteric-pricing by any means. They are also stout enough to drive headphones to a respectable level, so it was easy to test the board once I had it wired in. I also used a razor knife to physically chop the traces that connect the DSP's DAC outputs to the amp IC, just in case any noise was making out of the amp IC's inputs and into the DAC signals. May the unit's speaker-level outputs forever remain silent lol. The only thing connected to those DAC outputs is my pre-amp board.

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OK, so that's the pre-amp board. Mission accomplished there. It sounds fantastic and should provide a nice clean signal to my active crossover (which feeds the amplifier).

Last but not least are the additional rear inputs. The AUX input was super easy. There are 4 connections involved. Audio left, audio right, ground and detect. The detect signal basically just needs to be connected to ground and that will signal the DSP chip that AUX2 input is available. I just opted to make a wire harness and permanently connect the detect signal to ground since I wanted to use some pro-audio grade signal cable and plugs, and there's no such thing as a pro-grade 3.5mm TRRS (4 position) female receptacle which is what I would have needed to make the detect work properly. Besides, I would have then needed a male-to-male adapter to actually connect to my phone, and that's too much clutter. Blah blah blah. The short story is that the rear AUX2 input works fine and it is always enabled whether anything is plugged in or not. That's the trade-off for using pro-grade shielded signal cable (and using a shielded signal cable is of the utmost importance if you don't like ignition noise in your music).

The rear USB was not as straightforward. USB has 4 connections: 5V, ground, data+ and data-. The 2 data lines are actually shared between the front and rear USB inputs, with a couple of components missing for the rear connections. What this means is that you can only use one OR the other for data, not both (I could have switched some components off of the faceplate PCB and onto the mainboard to make the rear USB data work while disabling the front USB). BUT, you can get 5V power off of both without any trouble, so I made a charging harness that connects to the rear so that a phone charging cable (along with the AUX2 cable) can be routed through the dash and into the glovebox so they are out of the way when not in use.

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So, that's the current state of things. I have not yet installed this into my car. The dashboard that is in there now is all cracked to hell, and I have a nice crack-free spare in my garage. The RMT-200 will be installed as part of the dashboard swap, as well as some other maintenance items like replacing the on-board computer and fixing the leaking heater core. Life is sort of busy at the moment, and I prefer to wrench in the fall when it cools off a little so it will be a little while until I have a chance to really enjoy the fruits of my labor.

I hope everyone has enjoyed this gigantic post. Some of these mods are easy enough to do yourself so if you want 12V output or extra rear connections, you can have them if you own a soldering iron and some open-barrel terminal crimpers! The pre-amp outputs...obviously not simple DIY stuff you'd knock out in a weekend!


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## TypeSC2 (Sep 16, 2014)

That looks seriously intense, but also looks incredibly fun. I have been trying to figure out a way to add a sub and amp to my car without breaking the bank. How much do you think this stuff cost to do in the end?

James


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## bmwman91 (Jul 28, 2015)

TypeSC2 said:


> That looks seriously intense, but also looks incredibly fun. I have been trying to figure out a way to add a sub and amp to my car without breaking the bank. How much do you think this stuff cost to do in the end?
> 
> James


Parts and materials were in the neighborhood of $150 for one of these. The head unit itself was $250, although it looks like the price on that has gone up a LOT since last year. It worked out OK though since I had some spare parts and sold a couple of the boards to E30 guys...so my mods were not quite free considering the time I put into it, but it was close enough!

As for your plans, what kind of head unit & speakers do you have currently? A sub is usually really easy to add since you just need a single channel amp with speaker-level inputs...tap that into a rear woofer's wires as a source and you are usually good to go.


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## sdezego (Apr 23, 2004)

> ..but I am pretty sure that the actual content of my posts will provide good times for all.


Indeed! This is brilliant. 

You are correct in that there are a number of VW enthusiasts looking for a decent looking HU that appears Stock'ish but has all of the bells and whistles.

Nice work!


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## bmwman91 (Jul 28, 2015)

A few months ago I FINALLY got mine installed, and obviously I just now got around to posting the rest of the project's details on here. The big delay was mostly due to me combining the installation with a crack-free dash swap, and ordering all of the various HVAC gaskets and other special-order odds and ends that you find when removing the dash. Here's the old dash...it was getting a little ugly.










Initially there were some serious issues with alternator whine and ignition noise.

I ended up building a custom radio power harness so that the RMT-200 would be grounded on the big chassis lug in the trunk next to the battery (where my crossover and amp are grounded), and the constant 12V power for the RMT-200 also comes from the battery's positive terminal (with a 5A fuse about 8" from the terminal). That helped reduce the alternator whine a lot, but it was still audible and not acceptable to me. The harness was constructed from red & black 14ga stranded wire, tightly twisted with a drill and then fed into a heavy vinyl sheath for extra protection against damage. I ran it behind the HVAC controls and then down the center console/under the tranny tunnel carpet, under the rear seat and then up the rear bulkhead with the bundle of factory harnesses on the driver's side.

After consulting our resident expert, Luke, via PM he reminded me that my crossover (Audiocontrol 6XS) has an internal jumper for different ground isolation settings. So I popped it open and changed the jumper from "Ground" to "Isolated". Voila! No more bad noises, whatsoever! Maybe my custom power harness is not needed after all, but it sounds like the stock E30 radio power & ground connections aren't all that great so maybe I will leave it.

Here's how the deck looks in the car. It took a lot of trimming and test-fitting to get it flush in the HVAC panel!














































Also, to properly support the back end you will need to make a spacer for the metal bracket in the rear. The main part of it is 9.5mm thick, and then the little extra piece is 1mm thick. This will ensure that the the RMT-200 is properly supported so that it does not put torsional stress on the parts of the HVAC panel that you need to glue additional material to, and so that the bottom of the radio doesn't stick out of the panel. You need the little extra 1mm piece because of how the RMT-200's bottom cover sheet metal is stamped.



















I am working on acquiring another clean HVAC panel since I banged this one up a bit while modifying it. The defects are minor and I am probably the only one that will notice, but I still want to do a better one. When I do get the spare, I will document the modifications in here so that others can do the same if they want.

Also, I re-did all of the speaker and signal wiring. The speaker wires I had in there before were 12ga zip-cord. Those are out, and I made my own twisted-pair conductors from Belden 18ga wire (the black and white wires you see).

The RCA cables were also custom-made since just about every off-the-shelf cable I have seen is total crap in terms of shielding (either inadequate, or non-existent). So, I ordered up some Canare shielded 2-conductor microphone cable and Canare plugs (3.5mm TRS for connecting to the RMT-200, RCA for the 6XS). I trimmed everything to the perfect length and installed it. The Canare cable is burly as hell, and the braided copper shielding has 95%+ optical coverage (which is a very good thing). The plugs are also stout and have beefy strain reliefs. You can see the pre-amp signal cables running down the top of the tranny tunnel and under the rear seat. Since that is an area that can be stepped on and sat on, that is why I went with the Canare mic cable since it is designed for use on stages where rockers on 5-day coke binges are stomping around.




























I also trimmed the RCA cables between the 6XS and amplifier to be the perfect length so that there is no slack or slop to deal with back there (I'll try to get a couple of pics tomorrow). Man, this RMT-200 mods thread is starting to turn into my audio-overhaul 2.0 thread!

Here's the Canare mic cable that I used:
http://www.performanceaudio.com/item/canare-l-2t2s-2-conductor-microphone-cable-black-/19004/

The Canare 3.5mm plugs:
http://www.performanceaudio.com/item/canare-f-12-stereo-1-8-3-5mm-mini-phone-plug-trs-/441/

The Canare RCA plugs:
http://www.performanceaudio.com/item/canare-f-10-deluxe-clamp-rca-plug/437/

The Belden 18ga wire was acquired at a local surplus electronics store. It's legit stuff, rated for 300V and 105 Celsius operation. While that may seem "thin", it is plenty heavy enough for the mids and tweeters that is connects to the Amplifier. The subwoofer still uses 12ga zip cord since it is about 14" away from the amplifier in the trunk.

Time for more pics and info. Since some folks are interested in buying the remaining spare boards that I have laying around and they want to do the installation themselves, this post will serve as the how-to for soldering things into the correct places and other installation-related topics.

First off, none of the soldering involved is terribly challenging for anyone with prior soldering experience. The smallest component involved is an 0805 chip ferrite, and there are some 24ga wires as well (which are probably the bigger challenge). However, a couple of the places you will be soldering to are connected to big ground planes, which require a lot more heat than signal pads, and of course this thing is made with lead-free solder which is the bane of everyone that owns a soldering iron.

Do not let this be your first soldering experience. If you have not soldered before, either find someone that has, or practice with scraps first. You can get little prototyping boards very cheaply at local electronics stores like Radio Shack. Buy one of those, and some 24ga stranded wire, and maybe some other miscellaneous components. Practice soldering them to the proto board first to get a feel for how the solder flows and fills. Also watch an hour's worth of Youtube videos on how to solder surface mount components. "Winging it" is not worth messing up your expensive radio, so study up and practice.

Here are the tools and materials that you will need:
1) 15W soldering iron, 25W is better
2) (optional) A second soldering iron, 15W or 25W. Removing one of the surface mounted electrolytic caps will make installing the 24ga signal wires a LOT easier, and using 2 irons greatly reduces your chances of ripping pads off of the board (and repairing that sort of thing suuuuucks). Dual wielding brah!
3) Precision tweezers
4) Rosin-core solder (I like Kester SN63PB37 #66/285), 0.031" diameter. Just about anything will be fine though.
5) Liquid flux or flux paste (no-clean type preferred)
6) Digital multimeter for checking continuity (beep beep)

Start by removing the main board from the RMT-200. See my first post for info on this.

If you are installing the chip ferrite to enable switched 12V output, install the ferrite in the location shown (circled in red, already installed). Try not to hit the big capacitor with the iron since that kind of heat is bad for it. Yes, the power wires are already installed in this image...BUT, install the ferrite first because those power wires will be in the way otherwise!









Proceed by connecting the power lines. Here's where each of the 3 wires goes. For these 3 (and the next 4), heat up the existing pad to melt the existing solder, and then add a little bit more of your own solder. Apply some flux to the exposed metal of the wires, re-melt the new solder blob you made and stick the flux'ed wire in. Note that wires' the insulation will probably melt a bit near the end where you are soldering.









Here are the wires installed. Note that I encased them in hot glue. This is probably unnecessary, but I really don't like to have solder joints carrying fatigue stress from vibration. If you want to do the glue step, don't do it until after you are completely done and have tested this thing out. Pulling the glue off could damage components it is stuck to, so consider it permanent if you use it.









Next, connect the 4 signal lines. I highly recommend removing the capacitor that is circled toward the top of this image. Doing so makes it a LOT easier to get the signal lines in place. This is also why I recommend having 2 irons. Also, when you put the cap back in place, make sure it is oriented the same way because this one is polarized (has + and - terminals). Nag nag nag...don't forget to put that cap back!









Again, here's the finished product. Same story with the glue.









After this, use your multimeter to make sure that none of the signal lines are shorted to each other, adjacent components, or ground. Also make sure that the white and gray wires are not shorted to ground (the black wire).

Now it is time to mount the board into the chassis. This should be very self explanatory.









Don't forget the nylon washers between the PCB and chassis.









When tightening the nylock nuts, do not go too crazy. You don't want them so tight that they mash up the washers between the PCB and chassis. Tighten them enough so that you can be sure that the PCB cannot move around, but don't go nuts (bad pun).









OK, your pre-amp board is now in place. Before reassembling things (you don't need to put the CD transport back in yet, but when you do, make sure that it isn't mashing any of the wires you soldered), connect the radio to the harness in the car and make sure that the 3.5mm TRS outputs are working and sound good. You can connect headphones to the 3.5mm connectors to test this. Also, you should hear the relays click ON about 2 seconds after the radio powers on, and they should click OFF at the same instant as the radio turns off (either with the power button or by turning the ignition key off). There should be no audible pops or thumps at power on or power off except in one case: when power is lost because you unplugged the radio while it was on (or disconnected the battery). For that last case...obviously don't do that, for lots of reasons.

The final step is to cut the sheetmetal top cover a little bit so that the two 3.5mm connectors' wires will fit through. You can do this with a Dremel or tin snips. Just make sure to file the sharp edges off (far away from the radio so you don't get metal shavings in there!). Once you have a nice clean cutout, zip tie the output wires into place as shown in the image above, reassemble the unit. Good to go!

If you also bought the switched 12V pigtail, here's the deal with installing it into the rear connector. To insert the terminal, just pop the little yellow lock strip out with a tiny flat blade screwdriver. Put the terminal into position #2, facing the same way as the other terminals on the bottom row. Once it is seated, put the yellow lock strip back in. Now you have 12V switched output for remote turn-on (this will only work if you installed the chip ferrite in the first step).




























And finally, for those that want to build their own high quality RCA cables, I made a quick little hand drawing showing what I did when I built mine. These work great, and I sleep well knowing that the shielding is excellent. I bought a number of retail RCA cables of varying prices and brands to chop up and inspect, and they were basically all garbage with lousy shielding. The cable that I am using is stage-grade microphone cable, so not only can it take a real beating, but it has an actual spec sheet and guarantees that the shield has at least 95% optical coverage in the braid (and braid is much better than spiral wrap). In a car environment where ignition noise and EMI are huge issues, you can't afford to use cables with ****ty shields around a single-ended signal like this.

Also, yes, I am running left and right signals through a single cable. No, this is not a problem and you will not have cross-talk issues. There is nowhere near enough current, or high enough frequencies, involved in this application to make crosstalk a concern. All connections in this are done with solder. See my post slightly above this one (#95 in this thread) for an example of one of the plugs, as well as links to the plugs and cable that I used. The total cost of the 2 3.5mm plugs, 4 RCA plugs and ~40ft of mic cable was less than one 12' Monster RCA cable, and the quality is vastly better. These will also be the perfect length for your car since you can measure and cut them to fit exactly right.

Once you have soldered the wires to the plugs, use your multimeter to make sure that none of the wires are shorted to ground or each other (the wires have very fine stranding and one could be sticking out as a "whisker"). Also make sure that the segments of the 3.5mm plug have continuity to the proper parts of the RCA plugs.


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## bm9703a (Mar 10, 2006)

To change the color to orange, are you actually soldering on new LEDs?


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## bmwman91 (Jul 28, 2015)

Correct, the surface mount LEDs were swapped for ones of a different color.


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## E Coded (Aug 28, 2000)

I would give my first born for this. :thumbup:


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## vwpeacewagon (Sep 29, 2016)

*switched power coneector*

Which one is ISO connector for the switched power? Is it the top left yellow Connector?


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## MCPaudiTT (Nov 26, 2006)

*OP, If you are still out there...*

Can I buy one of the PCB's, and do you have a parts list for the components? Or can I buy a populated PCB?

Please email me at mmphill -at - gmail (dot) com


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## IFlyGTI (Feb 26, 2001)

MCPaudiTT said:


> Can I buy one of the PCB's, and do you have a parts list for the components? Or can I buy a populated PCB?


Ditto. I always feel a little giddy when I see certain threads pop to the top of my subscription list with updates & yours is definitely one of them. Giving this some serious thought as a replacement for the Kenwood deck in my Mk3 & since I'm streaming more & more from my phone as of late...


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## bmwman91 (Jul 28, 2015)

Wow, a blast from the past.

MCPaudiTT and I are corresponding via email. IFlyGTI, I will shoot you a PM.

There is one thing that maybe you guys can help me with. The FM radio reception is terrible in my car. I assume that this is because the RMT-200 was designed to work with an amplified antenna. Do any of you have a link or image of the wiring diagram for the cars that these head units were used in? I would like to see how the factory antenna wiring network was designed. Thanks!


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## IFlyGTI (Feb 26, 2001)

That's gonna be a tough one given that it was never used here in the States & I doubt an overseas VIN would bring anything up in Elsa. Have to see if my source on the deck can track anything down on that.


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## bmwman91 (Jul 28, 2015)

Got it. Well, in that case I will just have to rely on US VW owners with the RMT-200 to tell me how their radio reception is and then maybe I can look up the wiring for those cars that seem OK.

I have been looking at the antenna base for the MK4 Jetta since it sounds like the OEM ones are in fact amplified and intended to be powered by 12V provided over the signal wire in the antenna coax. I went out and measured the RF signal wire (central wire in the long coax cable between the head unit and antenna base) and the RMT-200 does in fact supply 12V over this wire when it is on. The car currently has a 1999 Z3 stubby antenna and base installed, and this base is also powered / amplified. However it has a dedicated 12V input on a separate terminal, and my suspicion is that having 12V applied to the RF signal line is either no good for reception, or maybe it even fried the base. Anyway, this explains why the RMT-200 did not have the auxiliary 12V ANT signal enabled, since that signal was provided to the antenna base via the RF signal wire. The other option would be for me to do some more work on the RMT-200 to see if I can find and remove a transistor which applies the 12V to the RF signal line, and retain the BMW antenna base.

Part #2 is what I am thinking of modifying to fit into the trunk / rear fender of my E30 so that I can retain the original antenna mount location. These are cheap enough that I might just buy one to disassemble and confirm that it is what I need. Also, it is like 1/3 the cost of the BMW Z3 base, which is also out of production!
http://www.antennamastsrus.com/VW/VW Jetta 1999-2005.htm


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## bmwman91 (Jul 28, 2015)

Quick update. I am going to try my luck with these items.
https://www.ebay.com/itm/OE-Volkswagen-PASSAT-Antenna-BASE-MAST-1998-2005-FUBA-VW/331991011241 (will not be using the included stubby mast since I have a 16" one already)
https://www.ebay.com/itm/Antenna-Ca...Jetta-Golf-GTI-MK4-1J5-971-650-B/352560515404

The base, which I am going to have to disassemble and make a custom enclosure for, should be pretty easy to get into the right spot in the trunk and connect to the mast through the grommet. I have access to a network analyzer at work, and I am tempted to run some RF sweeps on this to see if it actually does anything lol.

Thankfully, a simple ebay search for "jetta antenna cable" brought me right to the second item. It looks to have exactly the connectors which are needed for this antenna base and head unit, and those cars all use the signal-line-powered amplifier bases, so I think that things should work out nicely. I am not sure how long the cable is, but if it is at least 4.8 meters then I can route it in the factory path. If if is shorter than that but more than ~3 meters, I can just run it down the center of the transmission tunnel with my RCA cables. The DC resistance of my stock BMW signal cable is ~6 Ohms (the conductor is 30 or 33 gauge...SMALL) which may be a problem if that wire is also intended to supply current to the amplifier. Maybe this one is the same, but for $30 I am willing to take my chances to see if it was designed to work better with this base.



Lastly, and feel free to remove this part if it violates forum rules, I have 5 of these pre-amp boards left. I am not a commercial entity and will not be producing more of these ever, so feel free to PM me if you are interested. I made extras mostly for other RMT-200 owners out there since (back when they were still available anyway) people really wanted pre-amp outputs and electronics are a hobby of mine.


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## sdezego (Apr 23, 2004)

You may have already found this out, but starting with the early 16v VWs (late 80's), VW started using the Fuba Beta D roof mounted Antenna. This was indeed amplified and in the same genre as your E30. In fact, didn't the E30 come with a front roof mounted Fuba? I thought I recalled that and even crafted my Old Scirocco in that fashion. stretching brain cells tho...

Anyway, the Corrado used the Fuba as well. The harness has the small Coax, but also carries a separate wire for the Antenna Amp which it was indeed powered by 12v. I can get some pictures if this helps. and I very well likely have an old harness laying around (possibly a Fuba base). 
Send me a PM if this is of interest. If I have what you need, you can have it for free in support of this amazing work.


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## 'Hassan' (May 27, 2002)

*Great Write Up!*

Just found this thread via Google search, as I wanted more information on how to rig the wiring harness. Wish we had meet at the right time, I would've traded my orange display for your white one  (just nabbed a new RMT 200 unit on Ebay). 

There's one left!!! https://www.ebay.com/itm/153445132596 :thumbup:

I'm currently searching for a PNP harness that will accommodate a simple 4-6 speaker setup... not interested in running any subs, amps or such.


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