[mix4fix]

I recovered a small portable headphone amplifier. It has no markings on it. I am unable to research it.

It has short male and female 1/8 inch TRS standard headphone cables. It has two lights: a red one when a power supply is connected, and a green one that never lights up. The volume knob that clicks on, and volume goes up.

12VDC wall wart supposedly came with it. When connected., red light illuminates red and green light never illuminates. I tried different 12VDC power supplies.

When I opened it up, it has a batter pack with 5 AAA batteries wrapped together.

My only option is to try considering replacing the battery pack. five AAA equals 7.5VDC-ish?

[FullRangeMan]

Any photo ?

[newzooreview]

If the battery pack is NiMH or NiCd, which is likely for an older device, it is 6V wired in series (1.2V each rather than 1.5V for alkaline).

So the 12V power supply likely just charges the 6V battery pack via a step-down converter/regulator in the amp.

It seems most likely that the rechargeable batteries are spent and need to be replaced. When replaced, they will charge, green light will come on when done charging, and device will work since it needs functional batteries even when plugged in to the charger.

Other things could be wrong, but getting a new battery pack would likely be part of, if not all of, the solution.

[mix4fix]

Went to Batteries Plus. Battery pack is bad - 4.2VDC.

They mentioned a generic battery pack that is 6VDC. They were out of it. Didn't go to any other location.

With the battery removed, and the wall wart plugged in, there is no red light. The next time I am out, I will look for that generic battery pack and give it a try.