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Old 20th October 2007, 12:14 AM   #1
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Default Onkyo M-504 problem eeek

Hello, I hope I have this in the right place. I have an onkyo integra m-504 power amp. The one with the dual monoblocks in one chassis. Everything lights up except the servo operation light, the meters are peaked at the 500 watt place, no sound output, and I can't hear the relays kick. When you leave it on the heatsinks still warm up and looking through the vent holes on the top you can see eight red led lights. I just got it and I can only hook up my ipod to it and use the ipod as my volume contol (doesn't work so well since there is no sound output lol). Does anyone think they might know what is up and help me out? Any help is greatly appreciated!

Dan
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Old 20th October 2007, 12:19 AM   #2
kevinkr is offline kevinkr  United States
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You sure your iPod does not have some dc on its output? Try turning the amplifier on with the iPod not connected to the amplifier.
If that solves the problem you'll need to figure out how to deal with the dc from your iPod..
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Old 20th October 2007, 12:31 AM   #3
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Yes, this was all happening before I ever hooked up the ipod

Dan
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Old 20th October 2007, 12:40 AM   #4
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I figured something else out though. If you turn off the amp the meters stay pegged at 500 watts but if you also unplug the amp from the socket the meters slowly drop back to the bottom end. If you then plug it back in the meters stay at the bottom until you power the amp up. They then go back to being pegged at the 500 mark. I hope this helps. Oh and I forgot to say thank you kevinkr for your input.

Dan
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Old 20th October 2007, 12:57 AM   #5
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There seems to be a problem with the protection circuitry. If you are not familier with electronics it would be best to have a qualified service man take a look. If you would like to know more about the innards, the schematics can be down loaded at: http://www.hifiengine.com/manuals_ty...kyo&mod=M-504. Good luck.
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Old 20th October 2007, 01:43 AM   #6
djk is offline djk
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It's fried, get the manual and fix it.
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Old 20th October 2007, 04:08 AM   #7
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I have some experience but not much. I got part way building a bpa300 chip amp. Never got finished though. How much am I looking at if I pay someone to do it (a guess). I have no skills at reading the schematics. How would I tell which components are part of the protection?

Thanks guys
Dan
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Old 20th October 2007, 05:50 AM   #8
djk is offline djk
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The amp is fried, not the protection circuit.
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Old 20th October 2007, 03:21 PM   #9
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How can you tell the amp is fried? I did a google search and a guy was having somewhat the same problems and everyone on that forum suggested the protection circuitry also. Well how much am I looking at replacing if the amp is fried, which is a bigger task the amp or protection section? If I had it professionally done how much am I looking at?

Thanks
Dan
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Old 20th October 2007, 07:27 PM   #10
kevinkr is offline kevinkr  United States
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I think the protection circuitry is doing its job and the amplifier has a huge dc offset on the output stage. The clue is that the meters are pegged - it could be that there are internal fuses and some are blown.

I doubt the meter and protection circuitry share much common circuitry other than power supplies. (low voltages ones at that) So it seems more likely that the monitored power amplifier circuits or some of the power supplies feeding them are the culprit

Take a careful look.. Read the safety threads here before you do ANYTHING!

Do not touch anything before checking to make sure that the supply capacitors are discharged. (Assuming you have a meter and can recognize them.)

It may be that there are some blown fuses on the one of the supply rails. Replace them with exactly the same type, but do not, I repeat do not just plug that amp in and turn it on - more damage may ensue.

Instead wire a lamp socket in series with one side of an extension cord to make a ballast lamp. Install a 100W bulb, and have a 200W bulb on hand. Plug amp into ballast lamp cable and turn it on, if the lamp dims after a few seconds turn off the amp and replace with the 200W bulb. If with the 200W bulb the meters return to 0 and you can hear the relays click measure to check and see whether there is dc on the amplifier outputs. (Should be less than 100mVdc typically.)

If you don't have a meter, don't know how to use it, either consider making the seller eat it or make them pay for the repairs.

Did you get it on eBay and if so did you use Paypal to pay for it? IF you did eBay and paypal will take care of getting you your money back. Silly for you to attempt to go beyond this point as it may cost you a lot of money to get it repaired.
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