Invertor causing a "buzz" sound

**fireball106** · 01-14-2005, 12:27 PM

Hello!

I just installed my CarPC: a lilliput 7" screen, Shuttle bardbone PC (200w PSU), and a 400W power invertor to power the PC. The PC has an Audigy2 card which is connected to a Rockford Amplifier. The lilliput is connected to the cig lighter.

I noticed the following thing: when I connect my CarPC to a regular power-socket (on the wall) - everything is fine.
When I connect my CarPC to the invertor, several things happen:

1. Many times the computer does NOT start. It starts only for a split of a second (I can see the LED) and immediately turns off. It takes several tries of pressing the PC power button until the computer really turns on.

2. When I connect the cable from the intertor to the PC (even without STARTING the PC) - I get a buzz sound from the PC. Attention, the PC is not started, and even though, I get a weird "electrical" buzz sound from the PSU.

3. At the same time, I get a horrible buzz sound (electrical buzz-clicks sound) from the tweeters. This sound does not change if I start/shut the computer, and does not change when I rev the engine.

4. However (a good suprise!), I am able to start the car engine and stop the car engine and my computer does not reboot (Means: I'm using Intertor and my CarPC survives the cranking).

Any ideas what could be the cause of these problems?

**tech013** · 01-14-2005, 12:41 PM

you have too much EMI interference coming out of the inverter

get a a/c power strip that has EMI filter that should help with the noise and

carputer not starting all the time also ground the computer ,inverter and lcd

to 1 single point on your car

**ColdPhreze** · 01-14-2005, 01:48 PM

it does not need to be grounded to the same point. The thing to do is experiment with different grounding points for each of thoes items and try to see if the noise goes away.

Also, it sound as if the inverter does not have sufficient gauge power wire, or maybe the ground to it is not good enough (did you scrape the paint off the metal where you attached the ground?).

ColdPhreze

**crazymadbastard** · 01-14-2005, 02:35 PM

Originally Posted by ColdPhreze

it does not need to be grounded to the same point. The thing to do is experiment with different grounding points for each of thoes items and try to see if the noise goes away.

Also, it sound as if the inverter does not have sufficient gauge power wire, or maybe the ground to it is not good enough (did you scrape the paint off the metal where you attached the ground?).

ColdPhreze

By grounding the 120v, does this mean the 3rd prong on the mains line on the inverter?

thnx

**KyferEz** · 01-14-2005, 06:20 PM

crazymadbastard, you are correct (usually). However, to make sure the inverter is not wired funny, make sure the ground pin and the case of the inverter are common using a multimeter on either resistance or continuity test. Most are, it's just best to be careful with 120v.

Also, the PC's power supply should be grounded. If the PC is in a metal case, simply ground the case.

KyferEz

**bazmangr** · 01-15-2005, 05:11 PM

I had the same problem with you,
I have a 600W inverter with a suttle PSU 250w. The problem is the PSU. I change it and I use a vary cheap noname PSU 300w. My pc now is working fine. But I had a other problem I have noise on the sound output (on board). I try some filters and now is perfect.

**fireball106** · 01-15-2005, 06:29 PM

bazmangr, this sounds VERY weird...
Can anyone confirm this? Suttle PSUs generating awful noise?

I have a Creative Slix case (which is actually a Shuttle case)

I noticed I hear sound on the speaker when the hard-disk seeks, I have induction from the computer components.

**malcom2073** · 01-15-2005, 08:13 PM

Alot of inverters will not run or go into overload mode if your battery voltage drops down too far. My car cannot idle and run my car-pc because the battery voltage drops too far. Inverters are horribly ineffecient things like that.

**fireball106** · 01-17-2005, 08:00 PM

Bump!

Has anyone encountered buzz noise, which was caused by the PC power supply? (this is a shuttle 200w power supply)

It's important for me to know, before I take my entire CarPC apart...

**KyferEz** · 01-17-2005, 08:22 PM

malcom, the cheap inverters _may_ have the problem you mentioned, however, I have used many different inverters and have never experienced any trouble such as you mentioned.

Trouble like you mention is likely caused by too small of a gauge wire to the inverter, or your charging system is taxed beyond what the little car can handle. Someone else I know has a car whose charging system is so horrible that when the bass hits the amps turn off. I have personally inspected his setup; the problem is that the altenator is just not powerful enough.

You may want to install a new pully on the altenator, which will cause the altenator to spin faster at idle speeds.

KyferEz