Blown chip??

[Dan2]

hey guys

i have this 4 channel car amp - it has 2 KIA6210AH chips in it. one day all 4 channels were working, and the next day one chip (2 channels) stopped working.

there is a DC offset of 0.5volts on the outputs of the "broken" chip and one of the 2 channels buzzes like mad when a speaker is connected to it. on the other chip the dc offset is about 0.01volts

i have checked the voltages on all the pins - the only differences between the working one and the non-working one are the output pins.

i was wondering if these chip amps can "blow" for seemingly no reason - because there are supposed to be a whole lot of protection circuits on it, and i was running it off a 10v 1A transformer, which is much lower than its maximum ratings.

 

[AndrewT]

Hi,
4channels off a 10VA transformer is asking a lot from the transformer.

Did anything get hot?
Usually the reason for SS electronics going bust.

 

[Dan2]

the transformer could not deliver the current to drive the amp very loud, but i was just testing it at a low volume with small speakers. the chips get quite warm without the heatsink - its a small car amp so it has a massive heatsink\cover. nothing else gets hot

 

[h3ad]

well to my understanding if u run an amplifier on low voltage it is going to draw more current correct?
so if it draws more current it is going to get hotter, and you mentioned using it without heatsinks... u may have cooked an IC

regards haydn

 

[markiemrboo]

well to my understanding if u run an amplifier on low voltage it is going to draw more current correct?

No.

As the impedance of the load decreases (8 ohms to 4 ohms say), you need less voltage but more current to achieve the same amount of power.

e.g... I think this is right, at least for simple DC figures

10W in to 8 ohms is 8.9V and 1.1A
10W in to 4 ohms is 6.3V and 1.5A

By running the amplifier at a lower voltage supply this won't change as far as I am aware.

 

[h3ad]

sorry honest mistake lol

regards haydn

 

[Nico Ras]

0.5V off-set does not seem to me that the amp has gone. Could a capacitor gone leaky and something that should be decoupled is now sitting at a dc potential. Take for instance the decoupling cap in the feed-back path.

 

[Dan2]

well i did replace 2 big caps (2200uF) one day before the one chip went haywire - u think that was a faulty cap that i bought??