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My amp blew one filter cap and some transistors and some mosfets.I replaced all 8 filter caps and transistors and the mosfets,but the protection led stays on. Where else do you think I can check? Your

I think one channel of my amp was short circuited on speaker output or overloaded with more speakers.

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  • Master
  • 924 Answers

You have what's known as DC Offset(a bad amplifier) you will need to check the drivers and all the fuse type resistors that are open. You need to check the rail voltages, both positive and negative, at the amplifier. You can't "shotgun" parts. You will need to check them. Be sure to reset the amp to factory defaults, but I doubt that it will help in your instance.This will be a tough repair if you're not an Audio Technician. You will need a Variac as well. For more information, or to inquire about a repair, please visit my website at audioserviceclinic.com. Thank you.

Posted on Nov 23, 2014

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6ya6ya
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Posted on Jan 02, 2017

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Cerfer39
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SOURCE: overload led on 2 channels

Hi Oranzky,

Will the overload LED's light up with the Speakers disconnected?

Posted on Nov 11, 2007

robotek
  • 1512 Answers

SOURCE: SoundLab SP500 Amplifier

I strongly recommend that you replace all output transistors at once, and the drivers also. Also look for arcing across small low value resistors about the output stages, and small signal diodes also for 0.6 volts barrier potential voltage(they often go short circuit also). soft start the amp with a variac if you have one, or an incandescent 60watt 240v(110v if in the US) lamp in series with mains power to limit the current that can flow to protect the amps circuits if there are still faulty parts about. Check
DC conditions everywhere you can. If both channels appear to be ok, Then some careful observation of voltages with a DMM will help you to find any more problems.
Amps by design with high potentials and direct coupling ascociated with DC feedback loops, make this sort of work hard to do even for an experienced tech as it is very easy to damage the parts you have previously replaced if you do not check things well enough before firing the unit up. Softstarting with a variac or some sort of limiting in the power supply are generally the safest ways to approach this sort of repair. If you dont think you are up to it, refer the work to an experienced audio tech, or hitme back here and I can assist you if you wanna have a crack at it. Cheers. A "fixya" rating would be great for my 2 cents worth here. :)

Posted on Jan 19, 2008

  • 4234 Answers

SOURCE: i have a yamaha amplifier in here for repairs, the

Measure DC to ground on the output transistors to check for any offset. The protect circuit is the least likely to be the problem. Post the readings here and I'll guide you from there.

Dan

Posted on Mar 11, 2009

  • 4234 Answers

SOURCE: crown amp had 2 shorted output transistors.and 1

There is a "driver" stage that sets up the voltages for the output stage as well as a bias circuit. Any of these can have a problem. I would suggest that you take voltage readings at each of the output transistor pins and post the readings here. I might be able to give you a few things to check. Crown designs are not the simplest to diagnose, but we should be able to track it down a bit. Measure each of the pins to gound and post the values here.

Thanks,
Dan

Posted on Oct 10, 2010

  • 174 Answers

SOURCE: carverm1.0thad 2 blown caps c401 an c402 replaced amp comes on but only half the rail volts hum in right channel low output left cannot find colprut can you help thx ed @just-audio.com

there might be a couple options, speaker broke, the signial left is okay but right you send it allready distorced ,

Posted on Apr 17, 2012

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