Car US AMPS USA-1000x with problems - diyAudio
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Old 13th July 2006, 10:30 PM   #1
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Exclamation Car US AMPS USA-1000x with problems

I am completely frustrated with this amplifier because i have spent a large amount of money on parts and then watched them blow up in my face. The amplifier, a US AMPS USA-1000x rated at 1000 watts rms is an incredible amplifer and is worth fixing. I originally got them amplifier from a friend with all 12 of the power supply fets (70n06) burned out with 2 signal transistors (MPS-a56) in the gate drive and 47 ohm resistors that connect to the gate. After i replaced all of this, the amplifer came on and played. I hooked it up to a pair of subwoofers and ran it at about 700 watts rms then it started smoking. I immediately disconnected the amplifier and ordered 6 new fets and replaced all four of the gate drive transistors mps-a06 and mps-a56. The amplifier then came on and played for about 3 seconds then the power light and output faded off until you disconnect the rem lead and reconnect it, thn it would repeat over again. I left the amplifier alone for about a week then hooked it up again. it played normally on a very small load then made a barely audible pop. now nothing comes on. The power light does not come on at all now and the amplifier draws massive amounts of current. The tl494CN pwm controller also gets hot. I disconnected pins E1 and E2 (the gate drive pins) and the microcontroller no longer got hot. I have since replaced every transistor in the gate drive and have checked both diodes and nothing tested wrong. I am getting -15 volts between the E1 and E2 connection on a voltmeter when the amplifier rem is on and no ic is in the tl494 socket. I believe the PIC flash eprom that stores the smart amp technology might be gone. I have heard that there is some way to disable its functions by clipping a few diodes?

Also if anyone has a schematic on this amplifier, at this point i would do almost anything for it.

Thanks for your time, Ryan
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Old 13th July 2006, 11:40 PM   #2
anatech is offline anatech  Canada
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Hi Ryan,
I moved this thread into car audio where I think you will get a better response.

A couple questions now. What impedance load where you running? Bridged? How do you know it was around 700W? Did you run it with a continous tone (sine wave)?

-Chris
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Old 21st July 2006, 03:53 PM   #3
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Default Amp testing

When you fire up a repaired amp it is essential to use a current limited power supply. I set mine at 2 amps and have no speaker connected when first firing up an amplifier.

If you do not have a current limited power supply, put a high beam headlamp in series with the power input. And fire it up with no speaker conencted. If the lamp glows brightly and stays lit, there is something else wrong you have not found.

Because not all the parts that fail show any physical distress and unlessyou use a meter to check the obvious ones you will not find them. There is a lot more to amp repair than just replacing the parts that look blown and mjabe shotgun replacement of other parts.

If you are not experienced at the procedures for firing up an amplifier after repair or have the equipment to do it right, you are just going to keep blowing up more parts. Myself, I would not even attempt it without a current limited power supply, multimeter and oscilloscope as well as the skills to use them.


Dan
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Old 21st July 2006, 03:58 PM   #4
anatech is offline anatech  Canada
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Hi Dan,
Quote:
Myself, I would not even attempt it without a current limited power supply, multimeter and oscilloscope as well as the skills to use them.
Yup.

-Chris
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