Has anyone done the line in stereo mod?

wrybread · Post by **wrybread** » 29 Apr 2019, 13:19

I'm using these instructions to try to add a line in jack on my s70:

https://www.matthewsvolvosite.com/free- ... o.html/amp

It's not really making sense though. I have the unit apart and I'm not seeing the connections they're referring to. Pics attached.

It says "Unscrew the four screws on the top of the head unit and remove the top cover. The tape unit will be visible.". When I remove the top cover I see the CD player.

Where the tape unit connected towards the back of the head unit is a little circuit card which connects the tape unit to the amplifier/controller. It is seated into the lower unit via a slip-on slip-off connector. Reach under the edge of this little connector card, which sticks straight up, and ease it out of its seat and out of the unit. This card is just a connector, and has no electronics on it. The card is labeled on one side, and labeled pins 3 – 5 should be, reading from the bottom of the card, GROUND, L, R

I have the card out, but don't see any labels.

I get ground on pin 5 (reading from right to left from the back of the card, which is the most zoomed in attached pic) on the connector jack with fewer (10 instead of 11) connections, so I wonder if that's it.

Alternatively is there some clever way to get the CD changer line in working, without spending over $100?

Post by **RickHaleParker** » 29 Apr 2019, 16:10

Locate the Tape Head and follow the wires.
The Tape Head has a Left channel (L), a Right channel (R) and a Ground (G).
Stereo audio has a Left channel (L), a Right channel (R) and a Ground (G).

wrybread · Post by **wrybread** » 29 Apr 2019, 16:59

There aren't any wires, just traces. And if anyone has any clues about which ones to follow, I'm all ears.

In other news I found this interesting video:

He gives a few clues but no source code or even links. I'll research the protocol he mentions later.

Edit: found this:

http://gizmosnack.blogspot.com/2015/11/ ... o.html?m=1

Post by **abscate** » 29 Apr 2019, 17:24

I think Volvo Mitsubishi Bus code is open source.

wrybread · Post by **wrybread** » 01 May 2019, 20:37

Well I built the Arduino-based CD changer emulator described here:

https://gizmosnack.blogspot.com/2015/11 ... o.html?m=1

I had the cable he used (8 pin DIN) on hand, and my car was parked a few blocks away, so I just built the thing without first confirming that it's the correct cable for my head unit. Here it is before testing (heat shrink not yet shrunk, wanted to test first):

But oops, my head unit, which I now know to be the SC-816, doesn't have an 8 pin DIN socket for the CD changer, it has some sort of 8 pin mini DIN, that doesn't appear to be a standard cable?

Hmm.

I'm assuming they're functionally the same, but I can't find a pinout for that socket, or even a cable for it. Here's the pinout for the 8-pin large DIN:

I don't imagine anyone has any leads?

I wonder if I can simply use a DIN to Volvo min-DIN adaptor, which I assume exists, but so far I haven't been able to find.

Does anyone know the process for connecting this to a CD changer? Does it only work with special changers? If not, it *should* be a readily available cable, and a standard pinout. But so far I'm not finding anything.

Thinking aloud, the pins I need are:

- melbus busy
- melbus data
- melbus clock
- left +
- right +
- common signal ground
- 12v + (also called "melbus run")

WhatAmIDoing · Post by **WhatAmIDoing** » 03 May 2019, 08:01

wrybread wrote: ↑01 May 2019, 20:37 Well I built the Arduino-based CD changer emulator described here:
...

Wow, now this sparked the nerd in me. Definitely keep us posted on this. I'm going to have to try this one myself.

Post by **abscate** » 03 May 2019, 08:30

Maybe your model is different but I followed the traces from the tape head to a solder point, then just attached the feeds there. L R GND are needed of course.

Post by **Goupil** » 03 May 2019, 11:25

WhatAmIDoing wrote: ↑03 May 2019, 08:01 Wow, now this sparked the nerd in me. Definitely keep us posted on this. I'm going to have to try this one myself.

Same, I haven't seen anyone that did this mod to a SC head unit, but still ordered the required parts

I don't mind a little bit of fiddling around to get it to work, as long as it saves me from spending 90$ in a Yatour !

wrybread · Post by **wrybread** » 03 May 2019, 11:51

Looking around a bit more, I think it might be a completely different protocol than the HU-XXX head units. I found this thread, which is interesting mostly because of all the links in it:

https://forum.arduino.cc/index.php?topic=510006.0

And this:

viewtopic.php?t=71911

Personally I don't really care if the head unit can control my phone or whatever, I just want the line-in.

configsys · Post by **configsys** » 04 May 2019, 06:38

I've been using one of the Grom-USA units in my V70R for years now. Impressed with the sound quality. Actually.much better than the FM radio stations. Can also take calls and listen to all your media from your phone.