tda7293 that blew

[1-3-2-4]

I'm curious about what things can cause this IC to blow.. would something like a short cause something like this to happen?

Long story short I was putting in a RCA jack and the center pin must of touched the shield after I heatsrinked it and I applied power, the other end was connected to a pre-out from a receiver.

 

[dr pepper]

Kapow.
That doesnt happen that often, I suspect something caused the internal output devices to short causing a small explosion, maybe the amp went unstable just beforehand, having a signal connected without a ground for long enough might have caused it.
Tda7293's are sometimes used in parallel, is that the case here?

1-2-4-3

 

[1-3-2-4]

I thought the tds7293 has a short circuit protection?

I will admit I was tired and I had to leave for a party and when I got back I tried working on it.. but I was checking it over and I found this.

in the first picture I noticed the pin and shield touching, but I don't think this alone would cause it to blow? since from that point on I had no shield ground connected on the cable to the amp.

It uses two for the sub in that case they are bridged and I think it is parallel

 

[dr pepper]

That wiring looks decidedly dodgy.
There is short protection and overtemp protection as far as I know, however these things are not indestructable, if the amp went into oscillation then temp rise can be very rapid.
There might be a stabilization network on the board, connected to the speaker output, a cap and resistor, if these parts show signs of being hot then thats the cause.
Could be either in your case, you've definately not had ground connected and most likely a short, if you sort these 2 issues out chances are it'll be fine with a new chip of course.

 

[1-3-2-4]

yeah I corrected it and I ordered two new chips which should be here next week, I guess the best way to get it out is just to cut the leads?

 

[audioguru]

Amplifiers in parallel do not increase the power to a speaker. Instead paralleled amplifiers allow a speaker with half the impedance (a 4 ohm speaker instead of an 8 ohm speaker) with double the power.

A bridged amplifier uses one amplifier to drive one wire of a speaker and uses a second amplifier to drive the other wire of the speaker out-of-phase. Then the voltage and current in the speaker are almost doubled for almost 4 times as much power as a single amplifier.

 

[1-3-2-4]

Once question.. being as this is bridged (sub is 8 ohm) why did only one chip blow? I assume if it was parallel both would of been out?

 

[audioguru]

A bridged amplifier does not have two amplifiers in parallel. Instead two amplifiers are Bridged.
When they are bridged then one amplifier drives one wire of the speaker and the other amplifier drives the other wire of the speaker out-of-phase. Then the voltage and current are doubled and the power is almost 4 times as much as with a single amplifier.

Maybe the blown up IC had its output shorted to ground?

 

[1-3-2-4]

You can see in the first thumbnail the shield ground on the white cable was *NOT* connected to the amp ground yet but the pin & shield from the input jack touched the pin that ran to the connection to the sub amp.. I'm about 90% sure this error is what caused the chip to blow, and what I meant when talking about the bridged and parallel, I was saying "IF" the amp for the subwoofer was connected parallel it would of taken out two of the amp chips instead of one right?