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Old 01-03-2005, 07:17 AM   #1
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Converter/charger humming in stereo

My Univolt was replaced by a previous owner by some other brand of converter/charger. Like a Univolt, I have the usual problem of a humming noise coming thru the stereo.

I tried connecting the hot wire for the stereo directly to one of the batteries, but this did not make a difference at all.

The stereo has a cheesy Radio Shack automotive type noise filter on it, which I've found to be useless in cars. I'm not surprised it doesn't work in an RV either. Stereo is also a cheesy Radio Shack AM/FM cassette, early 80's vintage, also installed by a previous owner.

Shutting off my converter while using the stereo is not a good option, so is there any existing noise filter I can buy or build by soldering together a handful of components?

I know this is a common problem so there must be an answer.

Thanks,
Christopher
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Old 01-03-2005, 08:20 AM   #2
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Not sure what compnents you can make yourself, but the noise suppressors of better quality are fairly inexpensive. Here is a link to a group of them. Hope it helps. I would think the 25a model might be the ticket.
http://www.crutchfield.com/S-46zQ2ry...p.asp?g=181150
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Old 01-03-2005, 12:54 PM   #3
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Have you looked into the other circuit's on the inverter to see if they are filtered? Changed from old univolt to newer to me used magnetek that friend had the battery noise looked into the filter option and was surprised but the inverter had 3 filtered circuits just moved it over buzz gone!
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Old 01-03-2005, 04:42 PM   #4
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Only got into the converter compartment once, just for a look, and it was a pain. Had to take apart most of the front sofa/bed to get in there.

Not planning on going camping any time soon. I suppose I could check for filtered circuits or maybe a filter switch built into the unit. Should probably write down any nameplate data while at it.

The noise filter from Crutchfield might also be a good option. I've bought a few car audio systems from them and they are reputable enough to take it back if it didn't do the job.

My long term goal is to replace the speakers and install a new unit with a CD changer. However, if I can't get that hum out of the line I might as well use a boom box.

In a few days I might work up the enthusiasm to take apart the sofa/bed and access the converter. I'll post an update at that time just to finish out this thread for anyone in the future who has the same problem.

Christopher




Quote:
Originally Posted by OakHill
Have you looked into the other circuit's on the inverter to see if they are filtered? Changed from old univolt to newer to me used magnetek that friend had the battery noise looked into the filter option and was surprised but the inverter had 3 filtered circuits just moved it over buzz gone!
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Old 01-05-2005, 08:34 PM   #5
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Update - converter/charger humming in stereo

The converter/charger I have is a Magnatek 50 amp, series 900, model 950. From what I understand, Magnatek makes one of the noisiest units around, and it's likely that no noise filter known to man can filter it out. Replacement is the only way to go.

BTW, no filtered outputs. This looks like a rather primitive model with only two leads out, which connect to the 12V fuse panel.

Checking a local RV parts supplier's catalog, I see a 55 amp model by PPC, and a 45 amp model from Progressive Dynamics. Both are supposedly filtered for quiet power and are similarly priced. Just wondering how I select the amperage since I have a 50 amp model which seems to handle the load, and the only models available are plus or minus 5 amps. Total up all 12 volt loads and get the next largest model?

Any comments on either of these brands would also be appreciated. I know that Progressive Dynamics is supposed to be good, but the PPC unit looks like it will be a better fit.

I have two house batteries which will be charged at the same time. Not sure how that affects things, if at all.

Now let's say I go thru the expense of replacing the converter/charger just for the sake of having a nice stereo system, and want to recover some of the expense. How much could I expect to sell the old Magnatek for?

Christopher
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Old 01-05-2005, 08:47 PM   #6
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Have you checked the ground? I had some issues in my car and when I actually tore it down, I noticed a bunch of crud bonded to the ground. Now when I cleaned it, it didn't totally go away, but it did lessen it. Maybe it could help?
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Old 01-05-2005, 08:50 PM   #7
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My old Univolt is 40 amp, it is more than sufficient for our little trailer. If I was to buy a new one, I would go with a 50 amp, or add 20% to what is there.
Have you given any consideration to losing some of the other cheese, and ditching the old radio for a newer model? Some of those Radio Shack (Realistic brand) radios also had an internal noise problem,, as well as not staying on station very well. I recently purchased a good JVC Am FM CD, with a detachable faceplate (good for long term storage) for around $129.00.
This also came with a built-in noise filter, and seems to work well.
Terry
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