HU-613 AUX input mod!

[crimsonv70]

Hey everybody,
Seeing as nobody has done this yet (without needing to purchase the CD changer or other expensive gear), I am excited to post my personal hack of the HU-613 unit for AUX input. I got really tired of using the tape deck sound quality and have been wanting to input my MP3 player for some time. The hack is fairly easy and should only take a couple hours (not including reinstalling the deck, which is a bit of a pain but there is a great youtube video by erievolvo that is step by step).

How it works: The main Audio control IC is an SN761026. It accepts all the audio signals and converts them to rear + front outputs, adds EQ controls, and the like. The inputs are switched via I2C controls so my goal was to figure out the tape deck input so I could just disable the deck and input my own audio source through there after selecting "tape" as the source on the unit.
Pins 2-5 are the Audio L inputs and Pins 47-44 are the Audio R inputs.
They correspond to each other and the input (for one side, L) is as follows:

Pin 2 = Tape Deck
Pin 3 = CD Changer AUX
Pin 4 = CD Player
Pin 5 = Radio



So, looking at the tape deck (it removes easily on its own) and tracing the signals, I found that the tape deck IC outputs to pins 2 and 47 respectively. The tape deck audio signal processor IC is an HA12216F. It converts the tape level audio to line level, reduces noise, and other stuff. Inputting a signal directly after that chip results in a nice balanced clean audio.

You can choose to either cut out the tape audio completely (who uses tape players anyway?) or, wire it up to a switching input stereo audio jack (that has 5 pins instead of 3) so when you plug in your MP3 player/phone/whatever it disconnects the tape deck audio. The only downside to the later option is that the soldering is a little bit tricker. The tape deck audio L out is along one tiny trace and requires some pretty good soldering skills. The first option can easily be done by a beginner.

The picture description:



HOW TO:

1) undo 2 screws at the top of the unit


2) undo one screw in the back (note: pic was taken after cover removed).
3) remove top metal cover
4) unplug CD player ribbon cable


5) unscrew 2 recessed screws that mount CD player module


6) unscrew 2 side screws that mount CD player module
7) pull out CD player module



8) feed audio wire (3 conductor or 6 if you want tape output) through one of the holes closest to the face of the deck. This is important because the metal mounting plate needs to squeeze over the entire deck later.

9) solder your wires
10) re-assmble everything


11) drill a small hole in the faceplate and screw in your audio jack (note, you can buy these threaded audio jacks with nuts at jameco.com or other places like mouser.)
12) you're done! I also recommend a zip tie to hold the cable in neatly.
13) install deck back into your car, put a tape inside (any old tape will do, this is just to activate the input) and plug in your MP3 player

Happy Hacking!

[crimsonv70]

Forgot to add, for those interested, the deck powers 2x LA4708N amps. the amp board plugs into the main board and is removed easily, with the CD audio outputs (post preamp) clearly labelled! So thats another alternative to the tape deck mod (maybe useful if your CD player is broken?):


Amp

Amp Board

Labelled pinout

EDIT: I was surprised that none of the amps have thermal paste for heat dissipation. I recommend putting a little on and it's really easy to do. Just unscrew the screws on the back plate, pull it off, and then you have access to the amps.

[vtl]

xcarlink is $80 or less, works fine with HU-613, installation time is only a fraction of your mod, does not require soldering iron. And you've got mp3. And steering wheel controls work too.

But, hey, who can stop inclined person?

[swimNdrive]

If using the CD output, do you need to put in a CD in the drive to activate the CD? Can you let me know the part number for the AUX plug?

This is a very good hack. The only thing I may do differently is to get the AUX plug install somewhere else. I would like to keep the cable away from the front.

The parts cost for this mode should be less than $10. For someone wants to have fun with electronic stuff, spend a few hours of time in a weekend is fun.

[Pennhaven]

Nice work! If someone had come up with the idea five years ago, I would have taken this route instead of buying the USA Spec I/F. This is cleaner, there's no need to find a place to mount the external interface and figure out how to route cables to and from, no potential for introducing hum from a poor interface ground, and of course it's less expensive. Yes, it takes some soldering work, but that's performed on a comfortable work bench, as opposed to mounting and wiring under the dash, and with the bench work comes the satisfaction of modding it all by yourself! And one other thing, there is no external interface to potentially fail.

Of course an external interface would still be the way to go though if you want to control an iPod with the vehicle's audio controls. But for a Sansa like I use or another generic DAP or smart phone this is a sweet solution.

[mapper]

Wow, nice work. Love when a person has skills and shares. If we had a "post of the year", I'd nominate this one for 2014 already.

[crimsonv70]

If using the CD output, do you need to put in a CD in the drive to activate the CD? Can you let me know the part number for the AUX plug?

This is a very good hack. The only thing I may do differently is to get the AUX plug install somewhere else. I would like to keep the cable away from the front.

The parts cost for this mode should be less than $10. For someone wants to have fun with electronic stuff, spend a few hours of time in a weekend is fun.

The audio jack can be found over here: http://www.jameco.com/webapp/wcs/sto...gDrillDownView

I took a look at my broken CD deck today and found a microswitch on the other side of the motherboard. I have a strong belief this is the switch that tells the unit to switch to CD audio. I circled the pins you would need to short in yellow (pic attached to this post). Without doing this you would need a CD in the drive to use the CD audio outs for AUX INPUT (sadly the HU-613 does not switch audio sources with the turn of the "source" dial. It needs a switch pressed for tape and CD to tell it to switch audio).

xcarlink is $80 or less

Thats a lot of money to me, in fact I bought this replacement deck shipped with the cupholder for <$60. I also didnt want to reroute cables into my glovebox or wherever, and then have to route another cable to MP3 player. I live in a major city where any exposed cables means "brake my windows I have an ipod."

Of course an external interface would still be the way to go though if you want to control an iPod with the vehicle's audio controls. But for a Sansa like I use or another generic DAP or smart phone this is a sweet solution.

I have a sansa so that is why I did this. Controlling an iPod with vehicle controls doesnt seem that great to me unless you make playlists and such. I always end up needing to look at the screen to select a song/folder anyway. Plus, knowing apple they will find a way to make newer units incompatible in the future (like the friggin video out 'security' chip needed for an ipod dock now).

Wow, nice work. Love when a person has skills and shares. If we had a "post of the year", I'd nominate this one for 2014 already.

Thanks it took quite some time to take all this pics and do the write-up, so I hope some people out there find this useful.

[frusterated]

Thanks it took quite some time to take all this pics and do the write-up, so I hope some people out there find this useful.

Nice guide! How's the sound quality and volume levels? I was looking around for something like this modification and saw some other radio models have some issues with static in the audio and/or low volume levels.

[Swagger XC]

Can I do this to an 803 or is this mod not compatible with the dolby system. I'm assuming it is.

[db130]

This is a great thread, thank you. I just did this to my HU-613 tonight. I went with a simple 3-terminal headphone jack instead of a 5-pin(I haven't listened to tapes in a loooooooooong time and I was perfectly OK with cutting the traces for the tape output). It was $3.49 at Radio Shack for a pack of 2.

The sound quality is surprisingly good!