Inverter / FM Modulator / Buzz

**ukchris** · 02-29-2004, 03:03 PM

Okay, I know this setup is far from ideal, but I'll not be buying an Opus for some time nor a new head unit, so this is what I have!

Now, when I listen to audio I get a nasty buzz... I have tried connecting the inverter directly to the battery and it was still there, although maybe reduced a bit.

If I power the PC from the house it goes away, so it seems to be grounding, correct?

Now... tell me if this is a real bad idea... heehee... if I connect the PC case to the black terminal on the Inverter it almost goes altogether. Is this a bad idea... should I ground the case to the car body instead?

Chris.

**TruckinMP3** · 02-29-2004, 03:39 PM

Yes the inverter and grounding is the issue.

The best it will get is grounding all components to the same ground point

Inverter
PC
head unit
and FM mod

Same ground connection for all of them.

**ukchris** · 02-29-2004, 04:12 PM

Originally Posted by TruckinMP3

Yes the inverter and grounding is the issue.

The best it will get is grounding all components to the same ground point

Inverter
PC
head unit
and FM mod

Same ground connection for all of them.

Is grounding the case to the -ive terminal on the Inverter ok? Nothing terrible going to happen..?

Thanks,

Chris.

**none** · 02-29-2004, 06:42 PM

Originally Posted by ukchris

Is grounding the case to the -ive terminal on the Inverter ok? Nothing terrible going to happen..?

Thanks,

Chris.

You SHOULD be doing this. Nothing bad will happen. These should both be grounded to the car as well. (I assume you are talking about the DC side of the inverter.)

**ukchris** · 02-29-2004, 07:00 PM

Originally Posted by none

You SHOULD be doing this. Nothing bad will happen. These should both be grounded to the car as well. (I assume you are talking about the DC side of the inverter.)

Yes the DC side and no, currently thry are just attached to each other, tomorrow I'll find a bit of car to ground them too though!

Thanks.

Chris.

**ares** · 03-11-2004, 07:29 PM

arg, bringing this thread back to life so I dont repeat the standard question.

I have a 300watt powersupply, powered by a tripplite inverter, along with a Inline FM modulator intended for XM satelite.

lastly is the stock headunit.

so long as the inverter is on, there is no stereo. period, no outside stations, no PC sound, I mean NONE. not static, not distorted, I just hear a hummm.

now the inverter is grounded to a 6gauge wire run directly from the battery. the powersupply is grounded to the inverter.... am I missing something here? the powersupply is plugged into the inverter, could someone expand on how I ground the powersupply to the same spot as the inverter? one is AC one is DC. or do you mean ground the power supply case?

in modulator is clearly an issue, as I grounded that to a ciggerette lighter. now both postive and neg are to the cig wires. can I leave the positive there, and switch the ground only? where would I switch it to? to the DC in line of the invertor? when you guys say "same place" do you mean like THE SAME PLACE, or just the same wire in general, I dont have to run everything its own line to the battery... do I?

and lastly the headunit... thats grounded to the stock location whereever that may be up in the dash, this is unacceptable? I need to cut its ground, and wire it back to the inverter so it can be grounded to the same 6gauge wire as the inverter?

please answer, Ive been working on this damn thing for a year getting one problem solved after another. dont feel like taking another 3 month hiatus while I sort another issue out.

**TruckinMP3** · 03-11-2004, 09:01 PM

It was working before you moved the ground?

I belive the answer is yes.

If so, undo the changes one at a time to find the one that is not right.

I know it is a pain, but one change at a time is the way to find it.

If you can ground everything to the 6 ga wire you have already.
The head unit ground I would leave for last, if line noise is still an problem try it.

Good luck and I hope that helps.

**ares** · 03-11-2004, 10:24 PM

I ran a 20gauge wire from the PSU case(a screw that goes through it and into the case) I ran another 20gauge wire from the inverter(again, a screw through the end, wired into that) and lastly I moved the ground for the inverter to the same place. twisted the 3 wires together and taped them into the negative side of the inverter line. right outside where the 12v comes in.

turn it on, nothing changed at all. not a damn thing.

so long as the inverter is on, its like a switch, on and the radio is gone, nothing comes through. doesnt really improve or worsen when the PC is turned on.

I guess what I should do is plug it all into an extension cord and make sure things work when theres no inverter involved. I havent tried that yet.

Im about to go try that then. but in the mean time, if this solves the issue, what do I do? the headunit not being grounded to that location cant be the entire source of the problem can it? cant keep it plugged into AC all the time.

**TruckinMP3** · 03-11-2004, 10:27 PM

Based on what you just said, you might not hace a grounding issue... but I am at a loss. post the results without the inverter. that may tell us something.

**ares** · 03-11-2004, 10:55 PM

ah this is great. well as you suggested I tried to isolate the problem started with hooking PC and screen up to AC power from the house. stereo still plays normal stations. good good, ignoring the fact that the inverter has the issue(you can turn the radio on and off with the inverter though, so thats still screwing up the regular radio stations.

so... try the PC sound, nothing that station is still a mix of hum and static.

alright test 1. plug earphones into the PC, got sound, good.

test 2. plug the modulator into an MP3 player. still that lovely humm.

so, narrowed it down, the modulator doesnt work. though there are other issues involving the noise with the inverter, taken out of the picture it still doesnt work.

go to the modulator box, it is a FM modulator from delphi for XM radio. it includes a 6volt out to power the XM station... it also says it turns on with the XM.

which leads me to beleive for the modulator to modulate, that 6volt cable has to be doing something, which its not.

looks like Im returning this bad boy. really too bad, cause it was perfect for the job, now I have to get a FM transmitter rather than an inline modulator.