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How do I splice in an rc filter with a 2200 microFarad cap and a series 25 Ohm resistor?

Posted on 2014-03-01
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Last Modified: 2014-03-01
Hi,

I've got a wireless headset for listening to my tv through the headphones, it has an fm transmitter that plugs into my tv/cable-box audio out.

The system works great on batteries, but I would love to be able to plug the transmitter into the outlet so I can just leave it on all the time.

Trouble is, with the transmitter plugged in instead of on batteries, there is a loud AC hum in the sound.

Looking around online, I found a comment from someone who experienced the same thing and fixed it like this:

"I cut into the leads from the power supply and installed an R-C filter consisting of a 2200 microFarad cap and a series 25 Ohm resistor"

Now, I know how to splice wires together - and I'm assuming I can get what I need at radio shack....

But what exactly do I need - is this a single piece, or do I need to get a 2200 microFarad cap and 25 Ohm resistor and put them together somehow?

A brief tutorial on what I need and how to do this would be very helpful!

Chris
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Question by:St_Aug_Beach_Bum
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Dave Baldwin earned 500 total points
ID: 39897521
Here is the basic diagram.  You need to get the parts and put them in the circuit like this to minimize the hum coming from the power supply.RC filter
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by:St_Aug_Beach_Bum
ID: 39897666
Got it, thank you very much :)
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by:Dave Baldwin
ID: 39897693
You're welcome.
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Author Comment

by:St_Aug_Beach_Bum
ID: 39897705
As I am looking up the parts here, I'm realizing these are just something I splice into the power cord. Do they sell ready made filters like this that I can just plug in and then plug the power supply cord into?

If not, perhaps the folks at radio shack can show me how to put it together :)
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Expert Comment

by:Dave Baldwin
ID: 39897715
The filter that you need has to go 'inside' the unit.  A filter on the AC power line won't help your problem and won't use the parts that you mentioned.  If your unit is two separate pieces with a 'wall-wart' power supply that has a cord connected to the transmitter, then you could probably install your filter in that cord because that's after the AC power is converted to DC.  Check and make sure the 'wall-wart' says that it supplies DC and not AC.
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Author Comment

by:St_Aug_Beach_Bum
ID: 39897734
This is what I am using for the power supply, as one did not come with the headsets/transmitter:

http://www.ebay.com/itm/221129993890?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
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by:Dave Baldwin
ID: 39897765
That looks fine.  You can either cut the cord to splice the filter in or find another box to put it in.  Another box requires another connector.  Or you can just split the wires inside the box to connect to the filter.  In any case, this is not just 'plug-in' thing, you will have to do some wiring and soldering yourself.  Do you have a friend that does things like this?
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Author Comment

by:St_Aug_Beach_Bum
ID: 39897912
Maybe... I'll ask around :)

Thanks again!

Chris
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