Amplified computer speakers don't work on batteries?

[themaritimegirl]

I have two sets of battery-powered speakers from the 1990's, one is a Koss SXM/11 and the other is branded Media Vision. Functionally these speakers are the exact same - they run on four C batteries (two in each speaker) or a 6V AC adapter to power the amplifier, or they can be turned off and run passively.

Both of these speaker sets have the exact same problem - they both work great passively, but as soon as I turn the amplifier on, they go dead silent. The power LED comes on, but the speakers are absolutely silent, even with the volume control all the way up. Turn the amplifier off, and they work fine as passive speakers.

The speakers are running on batteries when this happens. I don't have a proper AC adapter to test them with, but I think when a friend used them with an AC adapter a long time ago, they worked fine that way. It strikes me odd that both speaker sets behave this way, and I don't know if I'm doing something wrong or if by some coincidence, both sets have the same problem rendering them useless on batteries.

Thanks for any input on this matter.

 

[creepingnet]

Sounds to me like the electronics inside are bad, or the bypass switching inside the speakers is not connecting when in the "amplified" mode.

 

[Ole Juul]

Sounds to me like the electronics inside are bad, or the bypass switching inside the speakers is not connecting when in the "amplified" mode.

I agree. Check the amp inputs directly without connecting to a computer. You can probably just use a finger or screwdriver on the circuit board as a signal source. The AC adapter input might also be separated from the battery.

 

[themaritimegirl]

The amp definitely isn't switching on - there isn't the slightest pop or hiss when it's turned on, and going as far as to put my tongue on the input jack doesn't produce any. I guess if there isn't something obvious I'm missing with these speakers, then there really is something wrong with both sets of them. Too bad.

 

[MikeS]

Borrow an AC adapter.
Batteries OK?
Check for corrosion on battery terminals.
Adapter jack may be defective.

 

[themaritimegirl]

The batteries are fine and the terminals are clean (like I said, the power LED comes on). I found an identical pair of the Koss speakers, and they work absolutely fine with batteries. These could be the speakers that worked fine when my friend used them with an AC adapter a few months ago, so I guess it's still a possibility that the amp is blown in the ones that don't work on batteries, and they might not work on an AC adapter either. I still have to find one and find out. I might crack them open and see if there is anything visibly wrong inside.

 

[Ole Juul]

I might crack them open and see if there is anything visibly wrong inside.

For the one that presumably works with an adaptor and not with batteries, I'd pay particular attention to the adaptor jack. These things are pretty simple devices but nevertheless are typical dumpster fare so there's a limit to how much time they're worth outside of the learning experience which is always invaluable.