More Wiring Mystery

"MM54" (mm54mk2) 04/06/2018 at 23:31 • Filed to: FB RX7

3

8

Having finished up putting the stereo wiring in the RX7 back to stock, I went to put the radio back in and immediately realized that the DIN connector that goes to the amps had more pins than the socket. This makes sense, since there are L and R outputs on the radio and it is a single cable.

After scratching my head for a while (the factory service manual seems to totally gloss over the whole “there are two 6-pin sockets and a single 8-pin cable” thing), and searching the forums, it was revealed that, as suspected, there is a Y-cable which goes here. Naturally, I don’t have that.

I began to wonder - how do they have +12V, ground, and four speakers worth of signal “+” and “-” (which is 10 signals) in an 8-conductor cable? After not finding any usable information, I figured I’d just ring out the 6-pin plugs at the amps back to the 8-pin. It turns out (see below) that all the signal “-”s are bussed in-cable, as is the +12V and ground to the amps! This is strange, but it does mean that they only need 7 conductors for the formerly-10 signals.

Where does this leave me? It looks like (fortunately) the 6-pin connector to the amps matches up with the 6-pin sockets on the radio (which do have a pinout in the service manual). This means from the diagram I scribbled up below (yes the 8-pin is numbered backwards) I can make the missing Y-cable.

Sometimes having an electrical engineering degree and spending a lot of time at work tracing out undocumented wiring comes in handy

The downside is that I had to order the connectors (of all the crap I have laying around, 8- and 6-pin DIN plugs are not included) so the whole “put the stereo back together/in” thing will be delayed until at least Monday.

AestheticsInMotion > MM54 04/06/2018 at 23:55

2

My brain hurts.

But... Uh. Congrats on the impending stereo repair!

MM54 > AestheticsInMotion 04/06/2018 at 23:57

2

It will have to come out!

Akio Ohtori - RIP Oppo > MM54 04/07/2018 at 12:36

1

If it makes you feel any better, I get to spend today determining what the hell I was thinking when I designed this last year and then adapting it to a new project.

MM54 > Akio Ohtori - RIP Oppo 04/07/2018 at 12:38

1

Makes sense to me, the upper bus determines which color/LED and the lower determines which grouping you’re turning it on. Not sure what you’re doing with it, but looks like a good design, at least for the addressing.

MINIGTI > MM54 04/07/2018 at 13:34

0

Someone gave me a ride in an RX7 in the early 90’s when I was about 13. Main thing I remembered was the Audio joystick ha.

Akio Ohtori - RIP Oppo > MM54 04/07/2018 at 13:59

1

Thanks! Probably my cleanest design by far. I do blinky lights as a side gig.

MM54 > MINIGTI 04/07/2018 at 14:10

0

Nice, that would have been a GSL-SE (top trim level) to get the joystick! Having a base model (which I will probably retrofit the -SE stereo into at some point, I need that graphic EQ!) I have a jumper in place where the joystick would plug in. As neat as it is, I’ll probably leave it out since they’re hard to come by and really not that useful.

MINIGTI > MM54 04/08/2018 at 00:20

1

Completely agree it’s a preposterous design but so unique!