Sound Ordinance Crutchfield Audio Amplifier Early Failure

Thread Starter

Lumenosity

Joined Mar 1, 2017
469
Hello Boys and Girls,
I happen to have a Crutchfield Audio System in one of my vehicles and even though it's not that old nor has been used hard, it failed.

Out of curiosity (since it was junk anyway), I opened it up and did my usual visual inspection of the board and components.

To my surprise, I found a cracked 4855D Op Amp. There are 6 and only one appears to be cracked.

I have no idea if replacing it will repair it but it's worth a shot so I ordered a few of those and should get them within a week.

Questions:
When an Op Amp fails like this is it usually indicative that there's something else wrong? Why would an OP Amp crack like that?

Thanks
 

Reloadron

Joined Jan 15, 2015
5,454
Questions:
When an Op Amp fails like this is it usually indicative that there's something else wrong? Why would an OP Amp crack like that?
My guess would be a number of causes. Frequently we see a cracked. split or burned in half operational amplifier or other chip and what we are looking at is a symptom and not a cause. This is where a schematic is a really nice to have so we can look at what might have happened to cause excessive current resulting in smoke and a fried component. If a cheap and easy to replace component we can use a shotgun approach, replace the component and pray as we turn on power. The repair may work or we get to watch the same symptom do a repeat performance. Operational amplifiers as well as other chips generally crack from excessive current generating too much heat, so what caused the current is the problem.

Ron
 

MisterBill2

Joined Jan 23, 2018
6,065
I suggest checking the components associated with that device to see if a capacitor has become leaky, or a diode has possibly short circuited itself. Also check the supply voltage pins to be sure the supply voltage is OK. It may be that an output transistor has failed,with a base short circuit to either emitter or collector. You can compare the resistances with the similar transistors on the other channels.
 

MisterBill2

Joined Jan 23, 2018
6,065
These amplifiers also contain an inverter power supply to provide the higher voltage for the power stage, and so it is indeed possible that the IC got a higher supply voltage than it could handle. This points toward needing to check voltages. One bit of advice is to install an IC socket in that position, which makes changing parts much less likely to lead to trace lifting failures.
 
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