alternator "noise"

timtheenchanteruk · Apr 27, 2014

after complaints from the rear seats, I'm trying to solve a so far annoying problem.

Got a couple of DVD players for the kids, the plug in type.
recently there is some intereference on the picture, a slight flicker and lines. after a nosy, if the engines off, its fine, perfect picture, with it running, its terrible.

checked/cleaned all earths, and even run the player direct from the battery, but to no avail.
Theres also a slight whine on the audio, which gets worse when the alt is under load.

is there a supressor or summat in the diode pack thats gone duff, or a suggesion of what to fit?

read a 3mF cap connected to the alternator output to ground would fix it?

timtheenchanteruk · Apr 27, 2014

m meaning micro..... cos i cant find the symbol...

listerdiesel · Apr 27, 2014

It's induced magnetic interference in the wiring, and may not be the alternator, my D2 does it on the 7" reversing monitor we have on the big trailer. I suspect it is the ECU firing the injectors on my V8.

Two things you can try:

1) Fit a ferrite filter on the power leads to the DVD players, the sort of thing you see on computer leads, you can buy them to clip over the lead or wind the lead through in a single loop.

http://www.ebay.co.uk/sch/i.html?_t...or&_nkw=ferrite+suppressor&_sacat=0&_from=R40

2) Fit a smoothing capacitor across the supply leads at the DVD player end, something like 2200uf at 35V, with a 0.47uf 100V paper or mylar capacitor in parallel.

I've yet to get time to do either, it's the end of the month and I've got a lot to ship out, so 'play time' has to wait

Peter

listerdiesel · Apr 27, 2014

MFD or uf will get you there

µ = Alt + 230

Peter

Datatek · Apr 27, 2014

Got the same type of noise problem on my Transit diesel, alternator is already supressed and ferrite beads did feck all. Just use my MP3 player instead of the radio for the moment.

listerdiesel · Apr 27, 2014

The ferrites need to be as close to the player/radio as possible, but agree, sometimes the amount of mush going round the vehicle just can't be suppressed.

Mine stops instantly as soon as the ignition is turned off, exactly as described by timtheenchanteruk.

Peter

Datatek · Apr 27, 2014

listerdiesel said:
The ferrites need to be as close to the player/radio as possible, but agree, sometimes the amount of mush going round the vehicle just can't be suppressed.

Mine stops instantly as soon as the ignition is turned off, exactly as described by timtheenchanteruk.

Peter

Yep, mine stops as soon as the ignition is turned off, only occurs with the engine running, most likely the alternator on mine, it's done 152k miles so the brush gear may well be worn. Could also be the engine ECU I suppose, it's quite close to the radio.

brian47 · Apr 27, 2014

I've used a small alternator whine filter to feed the +12 volts to the bits for my added sound stuff.
It's a small inductor in a plastic box with three wires; +12v in, +12v out and a ground wire.
Fit it as close as possible to the kit giving the trouble.
About £10 to £12 on the bay.

Kwakerman · Apr 27, 2014

You could always try taking the alternator belt off and starting it, if the noise is still there on the screens then its ignition or similar, if its gone its being generated by the alternator. Obviously don't run for too long as you will have no water pump.

timtheenchanteruk · Apr 27, 2014

Ill give the ferrites a shot, think ive got a few floating about.
Not likly to be muich apart from the alt on mine, seeing as it doesnt have ignition

failing that ive got a couple of 12V stablilisers somwhere as well, IIRC they have some smoothing in them, should do the trick.

was just seeing if I could fix the cause, seeing as it used to be fine rather than fix the symptoms.

listerdiesel · Apr 27, 2014

My monitor is brand new, so no drying out of the smoothing capacitors inside, just looks like inductive interference.

I've just made the screen mount up to take it, and will be coming to the Landy bash with the trailer so first time out for it.

I'll be running it off the rear 12V socket and the video receiver will be at the back as well. Probably give it a run this weel.

Ferrites are best if you take a turn through the centre rather than just passing the wire through them.

Peter

alternator "noise"

timtheenchanteruk

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timtheenchanteruk

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listerdiesel

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listerdiesel

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Datatek

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listerdiesel

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