distortion at low volume stereo amp

[kasumyku]

hello everyone!

found a pair of pc speakers in recycling room( wrong place to discard electronics...) and hoped that wont work so I can learn more about electronics and my wish came true:))) but now I cant figure out what the problem is...

-symptoms:
sounds OK up to about 10% of the volume, anything after that sounds distorted.

-what I have checked so far:
1)looked for shorted wires, but doesn't sound like shorted wires because it sounds clear up to 10% of its volume
2) found a leaky capacitor, checked it with ESR meter, much higher resistance than what it should be... replaced bad capacitor and same symptoms...

Brain of this little amp is a TEA2025B chip... everything else on the board is only caps, 1 pot for the volume(also is for on or of )and 1 transistor which i pulled it out of the board and it checked good.

Any guidance would be much appreciated and thanks in advance!!!

[Greg Robinson]

1st rule of electronics repair: measure voltages!

[kasumyku]

1st rule of electronics repair: measure voltages!

Any wake up call its more than welcome, but guidance would more appreciated...

[Greg Robinson]

Well, have you actually measured voltages? If you did you didn't mention it, just testing caps and a transistor, something beginners will often do while forgetting about voltages.

[Tac Eht Xilef]

a) As everyone's mentioned, measure voltages. Without that basic level of troubleshooting you're not fault-finding, your guessing.

b) Dunno about that chip particularly but most similar ones of that time & ilk are notorious for either being really prone to supersonic oscillation unless the layout and surrounding circuitry is spot-on, or half-dying and distorting at higher volumes.

Voltages. Datasheet. Compare...

[SeanB]

Distorted sound means change the 100uF capacitors attached to pins 3 and 14. Use ones rated for 25V or more. That should improve things a lot, but it is still a pretty low fi unit.

Datasheet here.

http://www.futurlec.com/Datasheet/Linear/TEA2025.pdf