GC killed my mp3 player

[thomas997]

I just built the amplifier in the national spec sheet for the lm3875.

I have no pot or anything, just exactly how its shown in the pdf. 5,000 uF for the power supply 1,000 near the chip, if it matters. Power supply is giving me about 25V DC.

So then I hooked it up to a cheap speaker (8ohm however I did try a 4 ohm later), and played some music. It was working fine, loud enough with the mp3 set on volume 1.

Then the next day I hooked it up again and tried playing some stuff, volume a little higher. There was no music coming out of the speaker, and all of a sudden the mp3 player starts smoking.

I quickly unplugged everything but the damage was done... the mp3 player with volume on max can now barely be heard with all the headphones ive tried.

I opened it up and looked for any burned components but I cant seem to see any..

So what I want to ask is is there any protection circuit I can build so this will not happen again? Was it a problem with the mp3 player driving a too low ohm load maybe?

Thanks

[platenspeler]

Originally posted by thomas997
I just built the amplifier in the national spec sheet for the lm3875.

I have no pot or anything, just exactly how its shown in the pdf. 5,000 uF for the power supply 1,000 near the chip, if it matters. Power supply is giving me about 25V DC.

So then I hooked it up to a cheap speaker (8ohm however I did try a 4 ohm later), and played some music. It was working fine, loud enough with the mp3 set on volume 1.

Then the next day I hooked it up again and tried playing some stuff, volume a little higher. There was no music coming out of the speaker, and all of a sudden the mp3 player starts smoking.

I quickly unplugged everything but the damage was done... the mp3 player with volume on max can now barely be heard with all the headphones ive tried.

I opened it up and looked for any burned components but I cant seem to see any..

So what I want to ask is is there any protection circuit I can build so this will not happen again? Was it a problem with the mp3 player driving a too low ohm load maybe?

Thanks

Thomas

I would not have any idea about the cause of this accident without the schematic of your clone with power supply and resistor values etc.

I would not expect problems under normal circumstances,
especially with non-inverted amps (with input caps).

Maarten

[Magura]

Before you discard your MP3 player, try checking the volume potmeter. Ive seen potmeters go south on discman's and the like before when driving loads they didnt like. Many are so skimpy that when they see less than 32 ohm load they go south.

Magura

[thomas997]

Ok here it is. Standard stuff..

Transformer is probably 80VA or less. 1.5A fuse on primary.

Player was connected with one channel..


Would connecting the output of the player in reverse screw anything up? I dont think I did, but Im just wondering..


Its digital volume, so theres no pot in there...

thanks

[carlosfm]

Mmmmm...
Burned muting transistors on the output?
But with today's miniaturization that thing may have muting transistors inside a chip.

[platenspeler]

Originally posted by thomas997
Ok here it is. Standard stuff..

Transformer is probably 80VA or less. 1.5A fuse on primary.

Player was connected with one channel..


Would connecting the output of the player in reverse screw anything up? I dont think I did, but Im just wondering..


Its digital volume, so theres no pot in there...

thanks

I think there is a drawing error in the power supply section (diodes). But if you've + and -25Vdc on the board you probably built it the right way.

I recently opened up my new Netgear MP101 wireless music player, and was surprised by the level of miniturisation. Hmm, these circuits are not fun for DIY people anymore. There is only two serviceable parts inside, the board and the display ;-)

Maarten