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Old 8th January 2012, 12:28 AM   #31
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Did you check U100-U107 for DC offset?
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Old 16th January 2012, 05:43 PM   #32
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Yes I did and they had none but I will re-check today since I made an error in my last pin configuration when checking the others. Just to double check and confirm.
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Old 16th January 2012, 11:17 PM   #33
Dr Zeus is offline Dr Zeus  United States
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I had a similar issue with one of these amps. I somehow get the feeling people try to over-drive the input on these with bass boost, eq boost, full gain, and easy clipping. Something tells me the TL072 opamps cant take that much abuse, possibly due to regulated voltage levels or lack of protection on the opAmp inputs.

I even found one time that DC offset wasnt an issue, but the sound passing through was. If you throw a sine wave through the RCAs, you should be able to see the same wave of different amplitude on your scope; that is depending on the crossove and switch settings. In any case, if you have a sine wave on any of the opamp input pairs or outputs, then all 3 audio pins on that side of the opAmp should likely read something of the inputed sine wave. Again, I've found at least one case where a stuborn opamp had sound on input pins but nothing on output - not even DC, and the opamp was bad.
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Last edited by Dr Zeus; 16th January 2012 at 11:23 PM.
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Old 17th January 2012, 12:08 AM   #34
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These amps have problems with DC offset in the op-amps because there are so many in series and any amplification boosts the offset from the previous stages.

The op-amp will only have signal on all 3 pins of one channel if the non-inverting input has signal driven into it. If the non-inverting input is grounded (and therefore has no signal) and the input is fed into the inverting input, there will only be signal on the output of the op-amp unless the op-amp is driven into clipping. Then you may see signal on the inverting input but it will likely be very distorted.
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Old 12th August 2012, 06:43 PM   #35
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I have one of these amps T-30001bd which currently blew on me. I opened it up and from what little I believe 8 mosfets look like they opened up. The amp powers on just fine. just no sound. I talked to Rockford and that Quoted me $454 for repair. Is there anyone here that could repair this amp for me cheaper then that?
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