All,
The only way out of this kind of problem is to create a clean
power supply powering only the
equipment that is sensitive to DC
noise. Modified sine wave inverters are noisy beasts that can drive some electronic
equipment nuts.
Here is how to create a clean supply (for a 12V system). Everything you need will be easily available on Ebay. Be sure everything below is protected and fused because these large capacitors pack a wallop and can melt stuff if you short out the terminals or the downstream
wiring is not fused.
1. Add up the amp ratings of the electronic devices you wish to run.
2. Get a bridge diode with an amp rating a good bit higher than the amp rating of the devices you wish to run. What you will be doing is to run house DC through it to fully rectify the house DC into a new circuit to power your stuff. Get a bridge diode with a hole in the middle that you can screw to something. It will have 4 leads. You connect the input 12V to the two opposing leads marked with ~ (squiggles). The output comes off the other two leads and will be marked + and -.
3. Get one or more huge capacitors about 70,000 MFD rated for 35VDC and mounting bracket(s). These caps will be slightly over 3" dia and 4" high. for 24V systems you want to get caps rated for at least 48VDC.
4. Wire the capacitors across the output of the bridge diode, connecting + side of capacitor to DC + side.
5. Wire an ATC or ATO fuse holder with correct size fuse slightly lower than the amp rating of the bridge diode.
6. You might need to add a fuse barrier strip to separately fuse different items you will be connecting.
7. You want to build this into a
project box with a metal backplate. Mount this box in a cooler location in your
boat so the capacitors do not overheat. there are various
fiberglass and also waterproof boxes you can get. Do not use
cheap plastic boxes.
8. Run
wiring from your "clean" power supply to your devices. Be sure to not ground the minus side of the DC output to chassis ground of your rig or the
noise will come back.
NOTE: This power supply will be about 1 volt less than your dirty DC voltage (due to voltage drop across the bridge diode). If your house voltage is 13.8v, your clean supply will be about 12.8v (not enough to charge batteries). When disconnected from
shore power and
alternator not running you will be at 11vdc or less as
battery power drops. Be sure your equipment can run on that voltage. Do not try to run an
inverter of this, it won't
work, most inverters shut down at 10.5 vdc