I received this amp today and so far I have been unable to find any shorted power supply or output fets. Amp looks fairly pristine inside minus the output inductor which appears to have shorted. I need to either replace or rewind the one I have. Where might I be able to source the wire to rewind the old inductor? It doesn't look like a major short but it is deep enough inside that I'd rather repair or replace it than try to fix the short and hope it last. For the time being I have removed the inductor from the amplifier. Is it safe to power the amp up without the inductor to check for other faults? Is it possible to drive signal into it to see if it plays audio? I imagine it would be noisy without the inductor. What are the odds that the inductor shorted and there are no other faults? I have never rewound one of these before. Does anyone know if there is a section in Perry's tutorial that covers this?
I don't know if the feedback is taken before or after the inductor in this amp. If it's taken before the inductor, it should power up normally and the output stage should oscillate but you won't see anything that looks like audio. You could look at the square wave on the outputs. The audio signal would modulate the square wave if everything else is OK.
If you want to make a new inductor, you can get the cores from CWSBytemark. If you post a photo of the inductor, I'll try to help you find the replacement core.
If you want to make a new inductor, you can get the cores from CWSBytemark. If you post a photo of the inductor, I'll try to help you find the replacement core.
Well it took a couple weeks and a little bit of phone tag but audiopipe did provide me with a new inductor and they did it for free! Pretty awesome that they were willing to do that. Things like that don't happen too often it seems. Anyway I popped in the new inductor and the amp appears to be working normally. I'll know for sure when I get it into the car and drop a one ohm load on it.
Well I spoke too soon it seems. Put the amp in the car tonight and it was working fine at low volume but when I cranked the gain up a bit it started making this horrible noise through the sub. When I turned the gain back down the noise went away. Kinda reminds me of what happens to mtx amps when they have an intermittent shield ground but I am fairly sure I verified the shield ground was intact. Kind of a low frequency warbling tone. Oh well I will pop her back open I guess but not tonight. Too late and work is coming up too early.
Did some more testing today. I brought the amp back into the house and hooked it up to my power supply. I was using a 2 ohm subwoofer on the amp for my testing. I played the amplifier as loudly as my power supply would allow with no issues. I even hooked up another subwoofer in parallel to drop the load a bit lower and still had no issues. I was scratching my head like crazy at this point. I brought the amp back out to the car and checked my ground and power wires which were both good . I checked my rcas to make sure the shield ground from my headunit and line driver were still intact and they were. I decided to give it another shot and hooked it back up. I started with the gain at minimum setting listening to music. I slowly turned the gain up and the noise came back again. I decided to take the line driver out of the equation and see what happened. Well without the line driver the amp works perfectly. I'm guessing with the line driver hooked up I was just over driving the input of the amplifier which was causing the amplifier to produce that crazy noise. This amp appears to need very little signal to get full output. I've used the line driver with every amp I've had over the last year or two and haven't had this issue before. Even with the line driver removed I still had to turn my subwoofer output level down on my head unit and turn the gain down a bit from where most amps would need to be set at. Can't say I've seen an amp that was this sensitive to the input signal before. I'm just glad that the amp is working like it should now.
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