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Re: Climbing DC offset then protection mode
Firstly, check for conductive hold down glue about the output stages. This can cause the problem you have. Or there may be a failing component somewhere in the output stage of that channel. Check for leaky transistors,diodes an capacitors. You will need to remove semiconductors to check for leakage, If you dont have alot of experience faultfinding amplifier power stages, I suggest you take it to a NAD authorised service center.
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Your receiver has a condition known as DC Offset, meaning you have a damaged amplifier. That second relay click, that you don't hear now, is the speaker protection relay not closing, due to the damage.
If you're interested in having your receiver repaired, please visit my website at audioserviceclinic.com. You may contact me there. Thank you.
You unit has a condition known as DC Offset, which displays as protect. This offset condition is presented to the microprocessor IC(a computer within your Sony). This IC will not let you turn the unit back on until the problem is corrected. If you are interested in repairing your Sony, please visit my website at audioserviceclinic.com. Thank you.
Check for shorts in the speaker lines.The easiest way to do this is to disconnect all the speaker lines from the amp. Now, turn it on and see if it goes into protect. If it does,that tells you that the problem is in the amp. If it doesn't go into protect, reconnect the speaker lines one at a time until you find one(or more) that shuts the amp down. That would be your short.
you don't want to do this( bypass the protection0
that d.c. output will burn the coils in your speakers with out making a sound!! you have a biasing problem
or like you said a d.c. offset problem it is best to work on this problem with out a load on the amp, this will allow you to trace back where the trouble is starting at. caps will cause this sort of problem but leaky transistors can also do this, even diodes.
this will require an experienced trouble-shooter.
I discovered that there is a compatiblilty problem between the Bose receiver and the Sony amplifier. If I disconnect the receiver from the amp then the amp starts up normally. Apparently the receiver sends out a dc offset or a "thump" that the amplifier doesn't like and goes into protection mode. I solved the problem by putting a 1 second delay circuit between the receiver startup and the amplifier startup. A simple RC delay on the remote input to the amplifier solved the problem.
Hi most amplfiers have DC offset and short circuit protection. Since you have removed all the loads it should not have a short circuit on it, the other possibility is DC on the input so I would recomend trying disconnecting the inputs as one of them may have DC on it, however this is unfortunately unlikely. The most likely cause is that the unit has gone wrong and the power amplifer is faulty. One last thing you could try is too open the unit up and make sure all the cables and PCBs are connected properly sometimes a loose connection can cause this type of fault. Failing that, unless you know how to fault find electronics, you will need to take it to a repair center or replace it. Regards, Andrew
From the above symptom, it show that the output stage of the amplifier have some problem.The protection cct come in to cut off the amp. when the output shorted or have Dc voltage.( this is to prevent further damage to the amp. & speaker ).If you know how to repair , just check on the pwr transistor (with heat sink )or else send it to the repair center.hope it help.