M1-ATX Grounding

aeroanderz · 04-01-2008, 04:26 AM

I now have one M1-ATX in the dash powering LCD and HQCT. Before, I had only a voltage regulator fixing +5 an +12 volts, but that wasn't very good during cranking.. :/

Now with the M1, i'm getting engine whine in the speakers. This is porbaly due to the fact that the ground used for the HQCT is from the M1 and audio signals are grounded to the chassis.

So, my question is: Is it OK to connect M1-ATX GND output to chassis? (having the same ground potential on both input and output ground)

DarquePervert · 04-01-2008, 08:12 AM

Yes you can ground your M1 to the chassis.

NotYou · 04-01-2008, 12:04 PM

Where do you currently have the m1-atx grounded too?

It should be grounded directly to the chassis, as DarquePervert indicated. Make sure you use the same size wire as you used for the power to the m1-atx, and you have attached it to a solid ground. This means directly to the chassis (or car frame), not something that is connected to the car frame. (for example, the bolts holding the seats to the car). Make sure the ground conenction is BARE metal as well.

aeroanderz · 04-07-2008, 02:21 AM

The M1 is currently connected to the stock ISO adapter in the car. IGN, ACC and GND. This is the supplied wires on the INPUT side. On the output side, it drives my HQCT. The input signals to the HQCT are grounded to the radio frame/chassis. This is were i suspect the problem is. It must be that the ground level/noise is different on the HQCT output side than on the input side (all the logic in between). So if i gound BOTH SIDES of the M1-atx to same place (GND connection on ISO adapter which is connected to the radio frame/chassis) It should solve the problem.. This means connecting a black ATX cable to the GND connection...

I just don't want to fry the M1, so.. I'll give it a try this week!

MindDrive · 04-07-2008, 03:30 AM

i had a whine/hiss in my audio output much like the altinator noise, come to find out i had an open ground in one of my RCA audio inputs on my amplifier, a quick solder job would have fixed it, but come to find out the circuit board of the amplifier by where the RCA terminal block mounts to the board was cracked, so what i did was make up a dummy RCA terminal with just the outter part of plug (ground) and ran a wire to the casing of the amplifier which cleaned up the audio greatly resulting in no more whine/hiss... might wanna check your audio plugs as well as adjusting your ground location

aeroanderz · 04-07-2008, 04:19 AM

I'm quite sure all connections are in order. I switched from a voltage regulator to the M1 so the only thing that changes was the power supply to my HQCT.

NotYou · 04-07-2008, 01:08 PM

Sounds like you got a plan to try... worst that that could happen is stuff just doesn't power on 'cause it isn't connected to a ground.

Honestly, though, I would recommend running your own ground wire instead of the one in the harness. The harnesses are generally an 18gauge or thinner wire, and then there's also the factory wiring which will 18gauge at the most -- most likely thinner.

For a high-current device like the m1, I would have it's own ground that you make -- preferrably with 14guage or thicker wire. Same goes for the power cable. It might work fine now, but there may be a day when the m1 draws more current then the wire can carry, and that'll melt the wire/possibly catch fire.

aeroanderz · 04-08-2008, 01:49 AM

Since I'm powering ONLY my lilli screen and one HQCT, power consumption is really low. I do however intend to put a 2-5 amp fuse before the M1 just in case.

The problem with having new wires is that I have mounted the M1, The Lilli screen and the HQCT inside of the Stock Radio 2-Din shell. So the only connection to the car is the stock harness (and 2xRCA + USB + VGA). This makes the unit easily switchable. No changes are made to the car.

Schematic picture of install: