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Hello all,

I've been lurking around these forums for years reading on all sorts of topics. I finally got around to putting a nice system in a vehicle I plan to take to Moab next month and I'm having a bit of a problem with one of my PPI Amps. I had a bit of an accident when testing the output and I think I may have damaged the output transistors. Here is what happened:

I was testing each channel to make sure that they were working properly with one of my subs and I inadvertently dropped one of the speaker leads and it touched the frame (ground) of the back seat. I heard a loud buzz/pop in the sub, followed by a mild burning smell, followed by a popped 30A fuse. I have a secondary fuse holder in the back of the vehicle about 24-inches from the amp.

It sounds like what internal short protection the amp had did not protect the output and now I am getting a static/popping sound in the left channel. It is not terribly loud, but it is enough to annoy me. It is roughly the same volume regardless of gain and is present with or without the RCA plugged in. I dug around on Google and the best answer I could find was bad output transistors. I inspected the circuit board and there are no burnt components or traces. There are also no components overheating/shorted and the amp runs just fine on both channels aside from the static on the left channel only.

Is it worth getting a set of MJL21193 output transistors and replacing the 4 on the left channel? There are so many other components on the board that could have been damaged it will be a roll of the dice. It would cost me around $20 for parts or I can just scrap the amp and try to find something else.


Suggestions? Thanks!
 

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Hello all,

I've been lurking around these forums for years reading on all sorts of topics. I finally got around to putting a nice system in a vehicle I plan to take to Moab next month and I'm having a bit of a problem with one of my PPI Amps. I had a bit of an accident when testing the output and I think I may have damaged the output transistors. Here is what happened:

I was testing each channel to make sure that they were working properly with one of my subs and I inadvertently dropped one of the speaker leads and it touched the frame (ground) of the back seat. I heard a loud buzz/pop in the sub, followed by a mild burning smell, followed by a popped 30A fuse. I have a secondary fuse holder in the back of the vehicle about 24-inches from the amp.

It sounds like what internal short protection the amp had did not protect the output and now I am getting a static/popping sound in the left channel. It is not terribly loud, but it is enough to annoy me. It is roughly the same volume regardless of gain and is present with or without the RCA plugged in. I dug around on Google and the best answer I could find was bad output transistors. I inspected the circuit board and there are no burnt components or traces. There are also no components overheating/shorted and the amp runs just fine on both channels aside from the static on the left channel only.

Is it worth getting a set of MJL21193 output transistors and replacing the 4 on the left channel? There are so many other components on the board that could have been damaged it will be a roll of the dice. It would cost me around $20 for parts or I can just scrap the amp and try to find something else.


Suggestions? Thanks!
No, it's not just the MJL21193 PNP transistors (how do you figure?). Chances are you have damaged not only the output devices but also the driver transistors which are surface mounted. Also probably burned a couple traces and some diodes.

Basically you're wasting your time replacing one half of one channel's output stage.
 

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I second that.
 
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