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Old 25th October 2010, 05:17 PM   #1
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Default Infinity 475a water damage

I had a leak and got some water in my Infinity 475a amp. When I found the problem, the amp had turned itself on and ran the battery down to 8V.

I took the amp apart and there was alot of oxidation on the PCB on the input power stage section. I cleaned it all up and hooked up 12V and GND, leaving the remote on disconnected. The amp is pulling 0.1A and powering the remote on makes no difference. The power LED is not turning on. Any suggestion on how to start the debug. There are no burned traces or burned looking components. I started checking some capacitor voltages. I would see some at 12V and others at 0.3V (I'm thinking there is something wrong with the power up circuits)
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Old 25th October 2010, 06:06 PM   #2
tomchr is offline tomchr  Canada
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Location: Calgary
I suggest throwing it out. Honestly.

I spent a week trying to repair a Parasound A23 that had been damaged by water. It was given to me by a friend. It had been sitting below a glass table with a plant on top of the table. Plant got over-watered, and guess where the excess water ended up... I had the schematics for the amp so I figured I'd give it a try. I spent a week cleaning up the PCB, re-tinning vias, fixing broken traces. Within the first night I had the amp playing music. It sounded good, but there was this annoying crackle in the left channel (the water logged one) at times. I spent the rest of my time trying to find the source of this crackle and reluctantly had to give up. By this time I'd swapped all active components between channels.
I have the skills, the education, the experience, the tools and I was still not able to fix the problem. Very frustrating...

The A23 chassis now houses an amp of my own design based on the LME49811.

If you do insist on fixing the amp, get yourself a schematic or service manual and arm yourself with at least the basic tools - multimeter, function generator, oscilloscope and work your way one section of the amp at a time.

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Old 26th October 2010, 11:13 PM   #3
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Any pointers on how to get a schematic? I'm an EE and have a lab to debug in so that's not a problem. No water damage to the analog section of the amp, just the remote on and input power section so hoping it's not to bad of a fix...
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