Amplifier shot... Repair?

[Plutoman 10+ year member]

Alright, so my hifonics TXI4408 is shot. It goes into protect a few seconds after powering on. What parts of the board should I be looking at for damage? I've opened it up, and taken a look, but I've not been able to find anything wrong. I've never repaired an amplifier, though, so I may be in over my head. I'm tight on money as a newfound college student, so getting a new amplifier is out of the question. It's either this or HU power. If pictures would help, just let me know.

Yes, I have a proper ground, tried several HU's and multiple RCA's, and another amplifier powers on just fine with the same hookups.

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[dB-r 10+ year member]

Likely got a bad output transistor. Please post a pic of the inside of the amp and I will draw on it for you... LOL... Amp repair is not that easy, but Class AB amps are generally very easy to learn, Class D's not so easy.

 

[Plutoman 10+ year member]

There's the picture of the board. I left it large, so it's easier to pick out portions of it.

I'm starting into electrical engineering, so it's possible that I'll learn more about it in my classes coming up, but I think it'd be good to fix it now. I figure I might have a better chance than most to learn. If any more specific pictures are necessary, just tell me what you need ^^

 

[dB-r 10+ year member]

Here ya go. Standard Class AB amp. Similar to Sundown SAX-50.4. However the sundown amp uses Sanken output devices, yours uses ST TIP35C/36C. Probably IRFZ44N power supply mosfets. You likely have a bad output transistor. Check it with a DMM to find the shorted one. Whichever one is shorted is bad. Replace it and you are good to go. If you do not find a shorted output transistor, you have something else wrong with the amp.

 

[Plutoman 10+ year member]

Appreciate it! I'll start checking it out after lunch.

One more question for you - assuming I find a shorted transistor, how should I go about obtaining a new one? Would going to a local shop, and having them order it be best, or is there a website that I can order through?

 

[Johnny Law.Lulz 5,000+ posts]

Wow. Thats a great lil lesson. I never knew half of that.

 

[Plutoman 10+ year member]

Wow. Thats a great lil lesson. I never knew half of that.

That's what I thought too. I knew a few of the general things, transformers, controller, drive circuits. And where the capacitors were, but not what they were called. Quite useful. Like I said, I do appreciate it ^_^

 

[midnightg35x 10+ year member]

Here ya go. Standard Class AB amp. Similar to Sundown SAX-50.4. However the sundown amp uses Sanken output devices, yours uses ST TIP35C/36C. Probably IRFZ44N power supply mosfets. You likely have a bad output transistor. Check it with a DMM to find the shorted one. Whichever one is shorted is bad. Replace it and you are good to go. If you do not find a shorted output transistor, you have something else wrong with the amp.

Great reference picture for those new to repairing amps!