humming sounds coming from setup?! should i worry?

**BigGuns** · 04-05-2004, 11:11 AM

hi all, i got my carputer installed a few days ago, but im having problems with power

Im using a shuttle pc, connected to an invertor, which is linked into the ingition of the car via the fuse box. When the power its run like this, there is a loud humming sound from the PSU. Should i worry about it?

The pc puts out about 300watts intotal, and the invertor is meant to be able to handle 300watt load with 600 peak.

when the pc is connected to the mains power, its fine everything works (i think this is the same for when the invertor is powered directly from the battery).

**Defiler** · 04-05-2004, 12:28 PM

You're just getting electrical noise. There are tons of threads started on this subject. Do a search and you will find multiple fixes.

**Mastero** · 04-05-2004, 01:36 PM

inverter should be always connected to the battery directly fused...

Mastero

**wizardPC** · 04-05-2004, 06:10 PM

see, I was gonna say that, but he says its his power supply humming--not a humming sound from his speakers.

**samc** · 04-05-2004, 06:35 PM

Did you try plugging in other things to the inverter ? I'd take it out if the PSU alone makes your inverter humm.

**starfox** · 04-06-2004, 04:35 AM

As said above, make sure that your PSU doesn't hum when plugged into the mains. If it doesn't, do you have a square wave inverter (most 12V to 110/240V AC inverters are square wave as it's a lot easier to produce a square wave)?

if you do, you might need to remove the AC RF filters and suppressor caps from the AC input stage.. Short out the inductors and desolder the capacitors. Be aware that you'll be fiddling with mains voltage circuits, so please be very very careful when you do this.

Also, check if your inverter actually grounds the power supply. If you have a floating inverter (there's no ground pin on the output AC socket, or the ground pin isn't connected), you might need to ground the PSU enclosure to the negative car battery terminal / car chassis (if your head unit / amplifiers don't have floating line level inputs)

**BigGuns** · 04-07-2004, 07:29 AM

hi, the pc works fine when plugged into the mains. Sadly i do not have a sqaure wave invertor, so i have no way of test this.

Since the wires were installed professionally, im going to take it back to them and tell them the problem.
What i have trouble understanding in the setup, is how they managed to install the invertor to the ingition, without connecting it directly to the battery? - I think they have just connected it to the fuse box under the steering wheel, with a 20 amp fuse or so.

Im almost 100% sure that the invertor isnt getting enough power, and the PSU is humming because its trying to draw more power. I'll test something smaller connected to the invertor to see if i get any more wierd results.

Do you think it worth buying a multimeter, and seeing how much voltage is being produced, also testing the amps?

**starfox** · 04-07-2004, 11:23 AM

You won't be able to measure the voltage and current coming out of the inverter without buying a mains measuring multimeter. Don't stick a normal lab multimeter across the mains voltage, you'll just fry the internal circuitry. Same with current, measuring AC current is very difficult, and measuring the current getting to your inverter is also going to be hard, as most multimeters won't be able to read 10+A for more than a few seconds.

Ask them if they used a switched relay to power the inverter from the ignition. I hope they didn't connect the inverter to the accessory line

**BigGuns** · 04-07-2004, 01:24 PM

http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=2211297650 - this is the item i bought, it uses enchanced square sin waves.

From the tests i done i found out that theres about 12.2-14.8v going into the invertor, but going out is 240v. I believe the ampage is the problem here

any good ideas on how it fix that?