Audio Systems: 3.5 mm external speakers for cell/mp3 player, thump thump thump, ac dc adapter

Question
Hi, First, thanks for taking my question, sharing your knowledge and volunteering.
I just bought a generic battery/5v ac/dc powered plug in speaker system second hand at Goodwill. When I got it home I put in 4 AA as required. I turned on the speakers and they came on but there was a thump thump thump sound in a continuous fast beat pattern. I thought it was strange and perhaps due to weak batteries so I used a 5 volt ac/dc adapter as required and the same thing happened. I then suspected it might be a short in a wire or connection and I thought about taking it apart and checking it but I thought I better ask for advice first. One thing I tried was using a 5.5 or 6 volt adapter and the  steady thump, thump, thump turned into a long hum-m-m (a bit less unusual) The thumping sound is such a strange sound to me, I've never heard a pattern like that before, it's almost as if someone were sending a signal in that it's so regular and constant when the speakers are turned on. Can you give me some advise to try. I dislike this disposable society we find ourselves in, besides I am on a very tight medical handicap income and I can't afford not to try and fix it.
Thank you, Thomas

Answer
Did you test the speakers before you made the purchase.  Most Goodwill shops have a place where you can fire them up. I have seem customers bring in power supplies and batteries to check out the electronics before the purchase.  In your case I think the speaker's internal amplifier is defective. Maybe that his why they showed up at Goodwill!

Can you speak to the store?  Sometimes they will let you return them within a  2 week  period.

Sorry you are having this problem.

PS: Usually for powered speakers the power pack must be the dedicated supply because of current requirements.  You could try, perhaps, a power mod with greater current capacity.