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Old 2nd June 2010, 09:47 PM   #21
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Have you replaced any parts in this amp previously (parts that failed)?
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Old 3rd June 2010, 05:51 AM   #22
Londik is offline Londik  Estonia
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I suspect the output FETs have been replaced earlier (by previous owner). Maybe HIP4080 too, but since there's a no-solder socket its hard to tell.
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Old 3rd June 2010, 02:11 PM   #23
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What is the exact part number on the output FETs?
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Old 4th June 2010, 12:31 PM   #24
Londik is offline Londik  Estonia
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The FETs are IRF3710 and there's a IR logo on them, but i'm starting to wonder if I should try IRF3710Z instead?
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Old 4th June 2010, 12:56 PM   #25
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This is exactly what I'd expect of the non-Z version. There's no guarantee that the Z-version will work but I'd expect it to solve the problem.
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Old 4th June 2010, 08:19 PM   #26
Londik is offline Londik  Estonia
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Ok, thanks. I'll order some IRF3710Z-s and let you know if they solve the problem.
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Old 5th April 2011, 10:51 AM   #27
Londik is offline Londik  Estonia
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Forgot to tell you - the IRF3710Z transistors work just fine. Thank you again.

But now next problem with a same HIP4080-type amp. Changed all power supply FETs, half output FETs with IRF3710Z (other side IRF3710-s remained), HIP4080 and some protection diodes near HIP4080. Now the amp works again just fine but there's an audible whining noise coming through speaker. The pitch of the noise changes slowly and sometimes stops at all. If you move the PCB or any component on it the pitch changes. I've tried resoldering the PCB, but still no luck. Any ideas?
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Old 5th April 2011, 02:06 PM   #28
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That's normal for many of the hifonics amps. I'm assuming it's at a low level. It's generally not an issue because the woofers can't reproduce the high frequencies well and they're generally in the trunk of the vehicle which further reduces the level of the noise. Many class D amps have their power supply synchronized to their output oscillator but these have no synchronization so they whine a bit sometimes.
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Old 8th April 2011, 11:29 AM   #29
Londik is offline Londik  Estonia
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It is low level, about 800mV peak to peak, but louder than these amps usually are. There is also 1.2V DC offset.
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Old 8th April 2011, 11:56 AM   #30
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Did you try the DC offset pot to get the offset to 0.0v?
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