Hack OEM Stereo for GROM to AUX

I couldn't find where this is covered anywhere else, and I looked everywhere. In my search I've concluded that there are no straightforward GROM AUX adapters for factory install stereos as old as our 2nd gens... So I might have to make one myself.

 

A few things.

• I want a clean factory look, OEM spec.
  
• I don't care about CD's or anything other than a basic stereo and 3.5 AUX
  
• I have three donor stereos to get it right
  

 

I noticed that with or without CD player, the factory stereos for the second gen Legacy has GROM input. I have no idea and was unable to determine if it's a straightforward hack.

 

I have three stereos and two with the CD player and that's where I think it might be possible to take the innards of a CD GROM out and fit for AUX to GROM in on the standard head unit.

 

Here's a photo of the CD GROM and it's wiring into the CD unit along with a photo of ht GROM male and female plugs.

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130927-190814.jpg

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130927-191020.jpg

 

I hope someone can assist with this!

If you've got donors, just find the L & R channel wires, drill a hole in the back plate, and tap the wires... SHAZAM! CD now equals AUX...

 

Or is GROM circuitry more complicated?

I think you're dead on djfunk! I've spent the better part of the last two hours digging around to no avail. I ripped the guts out of the cassette player but I'm faced with figuring out which switches have to be active for the player to recognize there's a cassette present.

 

So I flipped over the circuit board of the CD player and yes! There's clearly labeled solder points directly associated with the wires, but I'm not sure what is what and how to make it work.

 

Here's the circuit board where the GROM wires up. It's the 8 pin (with only 7 present) as shown in the photo above of the circuit board and GROM.

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130927-214146.jpg

 

Here's the alternative...

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130927-214133.jpg

at the alternative pic.

 

For the cassette player, there should be a reed switch that closes the circuit. I have one from my former 99 OBS. I can take a peek if you need me to. In your picture, lower left corner of the "main board", that black plastic lever looks similar to most of the actuator arms I've seen on cassette decks which activate aforementioned reed switches.

Ok, interest peaked. I'll have no way of testing anything, but I'm cracking open the beast.... (i'm a sucker for "impossible")

Here's the many switches...

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130927-220310-624x832.jpg

It would be preferable to go the GROM route IMO. But I will take either, or BOTH would be awesome! I could do all kinds of shit me thinks lol

Here's where I am with the GROM.

 

8 pin lead with 7 pin present:

• in - left
  
• in - right
  
• out - right
  
• out - left
  
• ground
  
• remote in
  
• remote out
  

 

4 pin lead with 3 pin present:

• ground
  
• accessory
  
• built-in (remote?)
  

 

Seems straight forward. I noticed the HU doesn't have a CD button which leads me to believe the unit recognizes if a CD is entered? I'm not sure how these work.

Here's a similar break down with the cassette player.

 

7 pin ribbon of which I can only account for 6:

• ENDB (side b)
  
• ENDA (side a)
  
• ground
  
• 5v
  
• T.PLAY
  
• EQ
  

 

This ribbon goes into a board with two motors, and two sets of 6 wires going out. One set of six goes to the board with three switches and the tape reader, and the other set to a board with the smaller switches labeled EQ and TPLAY with all the gears, where the cassette is held in place.

 

The 3 pin ribbon which I have no idea about, goes into the board with the three large switches / tape reader and appears to go out to each switch separately and each switch leads to where the 6 wired leads enter that board.

 

GROM seems so much easier to work with if I just knew what the hell to do lol

NASIOC actually comes in handy some times...

 

http://forums.nasioc.com/forums/showpost.php?p=9457037&postcount=6

So close... 1) I'm not using a changer. It's the second half of a single DIN HU that is "bundled" together making a double DIN. 2) I have a 10 pin connector.

 

Looking through that thread (great find BTW), the 13 pin diagram looks far more involved than the 10 pin. There must be a way to just wire into it.

Another one from NASIOC - supports my theory as this 10 pin has no TXD / RXD pin labels.

 

http://forums.nasioc.com/forums/showthread.php?t=502568

You still have the 13-pin connector. It's just that there are only 10 pins used. 2 pins are labeled as "NC" for "No Contact/Connector".

 

http://www.surrealmirage.com/vrg3/bcstereo/

This shows that the pre PBUS units used a 4 pin setup, that could be bypassed.

lol - duh.

 

Wow that's a gem. This is what I need to get started on my hack. Thanks so much for your help, so far! If you have suggestions pass them along. Also, now that I have all this spare room in the HU light a cassette player, what to do?!?

 

btw I have two Panasonic and one Clarion - going with the pan for sure. It says Subaru on it

damn I just realized the CD player with the GROM I want to use is from the Clarion and it's a little different...

Ok, I must need to get to bed I'm not making sense to my self anymore lol. Loopy.

 

Since I am scrapping the CD player and I'm using a Panasonic I can just adapt the GROM for my needs?

 

In the diagram you provided that shows the 13 pin GROM and outlines COM, TRG, L, R - all I have to wire up is the L and R and trigger the HU to accept it's input, correct?

 

"TRG is the trigger line; to switch the radio from radio mode to external-input mode, apply +12v to this line" - I would need to create a switch that relays 12v for the TRG

 

"COM is the common line shared by the left and right inputs, and L and R are the line-level inputs."

 

I have no idea what a COM line would be for.

COM is short for "common". Its the ground wire. It is usually a black wire, where the line-level (or positive) is a red wire.

Ah. So the TRG and COM is where I create my switch.

 

Once I trigger the common wire that left and right share with 12 volts my music will play?

No. The switch will go on the TRG line. 12 volt input to switch the radio to "CD". EDIT: I would use a regulated source from inside the car. You could maybe tap a power source inside the radio itself... You'll also have to find a ground to complete switch circuit, unless the connector is already grounded to the radio. Hard for me to make that call without seeing the thing in person.

 

The COM line will get connected to the left and right ground wires from 3.5mm cable. The ground will be the bare strands once the first insulation layer is stripped from the cable.

 

The L and R pins will get connected to the positive wires from the 3.5mm cable. They'll be inside the other, insulated wire (once past the first insulation layer). EDIT: The inner insulated wires may be color coded for L (white) and R (red). Sometimes you get lucky, sometimes not.

 

Here is a really quick, and ugly/confusing, schematic...

I'm getting it, slowly lol. Here's where I am with my wires for tonight.

 

Here's the Clarions CD player (single-disc) DIN GROM

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130928-000638.jpg

 

And here it is prepped for whatever this entails.

 

http://2nd-gen-legacy.allthedeets.com/wp-content/blogs.dir/93/files/2013/09/20130928-000647.jpg

 

I had to break out the soldering iron to loosen the metal shroud covering.

Here's where I'm headed. Obviously I want aux using the OEM HU, but I have already wired up my dash with extra hidden 12v outlets including a hard wired phone charger, with the cassette tape player deleted, I can install the chip with two powered USB and audio in / out. Audio in for a travel mates iPod or my sons portable DVD player and audio out for travel stereo or something used external to the car but including the cars audio system. Lol. I will get carried away. I also have a small inverter under the dash but I'm experiencing some issues with it. I think it's the inverter...http://img.tapatalk.com/d/13/09/28/yve7epag.jpg

http://img.tapatalk.com/d/13/09/28/e9ahy3u9.jpg

 

 

"The only reason I look at other peoples cars is so I can see my Subie in the reflection." -Carver Snell

 

Sent from my stupidphone.

Nice!

 

Are those LM317s?

 

I was going to use those originally, but my project would be better protected with switched power so I'm using Dimension Engineering DCDC converters (DE-SW050).

No, d2012s and they are factory to the CD player's board lol. I don't plan to do anything fancy except wire the USB for 12v with car ignition pos on.