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Old 16th March 2009, 11:08 PM   #11
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Done!
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Non é mai abbastanza...
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Old 16th March 2009, 11:29 PM   #12
fjcbs is offline fjcbs  Portugal
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thanks aparatusonitus, you're The Man!

I'll give it a shot trying to find the problem or else, well it will go to the dealer for repair
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Old 17th March 2009, 12:08 AM   #13
dtm1962 is offline dtm1962  Canada
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Default S300 Repair

I have had the fast blinking lights which indicate that it in protection mode as a result of irregular voltages as a result of a component failure or bad solder joint.

Chances are the ZTX653/753 transistors have overheated and are leaking or a solder joint from top of board to bottom has separated. I resoldered all solder connections in the area of the discoloured circuit board surrounding these transistors and voila it worked again.
I have done the NAD recommended reliability modification via changing out the 4 resistors that allow these transistors to run cooler and more reliable.
These transistors are located on the main board and are the transistors that are grouped together with 8 small TO-92's together for each channel. You will notice the circuit board in this area has discoloured as a result of the excess heat. I have successfully repaired it without changing out the transistors so I conclude that the solder connection went bad as a result of the excess heat. Email me dmullins@cogeco.ca if you need more assitance.

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Old 17th March 2009, 08:46 PM   #14
fjcbs is offline fjcbs  Portugal
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thanks again dtm1962.

today after work I got home and redid the solder point where you said and my beloved S300 works again!!!

I will try to get some resistors to do the reliability mod and also some heatsinks as you mentioned.

The funny think is that last saturday I went to buy some Kimber 4TC cable to bicable my JMLab speakers with the current 8TC cable I had and as soon as I got home to set the cables connected the amp died! I don't think it was the new cable because the left channel was already making some unordinary noise...

Well, listening to the repaired amp, it sounds much more alive and "fast". Don't know if it is because of the repair job, the new cable or just placebo for me being capable to repair the darn thing all by myself!
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Old 21st April 2009, 01:59 PM   #15
krezov is offline krezov  Russian Federation
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Hey, guy's! I am from Russia, excuse me for my bad English. But my s300 have broken too, and our engineers can repair it, when they got service manual for it. Can't anybody help me with service manual?
Thank to all!

krezov@inbox.ru
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Old 21st April 2009, 08:40 PM   #16
dtm1962 is offline dtm1962  Canada
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Krezov:

I sent you the NAD S300 Schematics and the recommended circuit Change.

Let me know how you made out.

Thanks,
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Old 29th April 2009, 05:48 PM   #17
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Hi,

My NAD S300 broke... left channel "static" sound when I woke up in the morning (left amp turned on overnight)...

Disconnected everything from the S300... push power on, power led blinks fast and the amp never really starts up.

I would very much appreciate if someone can provide me with the schematics (and/or service manual), and some details about ths NAD recommended modification. I've read about a reliability upgrade, but I never actually understood what it is.

I've already sent the amplifier for repair, but I want to make sure they implement these recommended changes before they send it back to me... I don't want it to fail again... I miss my S300

Thank you so much for your help!
Sergio
(Portugal)

SergioRZ0@hotmail.com
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Old 29th April 2009, 08:59 PM   #18
dtm1962 is offline dtm1962  Canada
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Sergio:

I just sent you the NAD S300 Schematics and the recommended circuit Change.

Let me know how you made out.

Thanks,
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Old 11th May 2009, 06:42 PM   #19
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Hi,

thank you so much for this

I don't have good news. Spoke to the repair technician and it seems like all transistors from the left channel are burned, and the main circuit board is also affected (brownish).

He thinks it might be possible to recover the amplifier by installing all new transistors (he ordered them from NAD Canada), hoping the circuit board will hold and not leak any DC.

However it's not guaranteed that this will work. We'll know when the transistors arrive (it can take weeks, even months according to their experience). They put it toguether abd make the necessary measurement tests to make sure the board is ok.

This should be related to the DC Offset I detected, maybe 2 years ago. When turning the volume knob (not playing any music) the speakers cone would move quite a lot, front and forward motion. I was told it could be DC Offset, but the shop where I bought it said it was normal. Well... according to the technician, the DC Offset was the cause for this breakdown.



I hope NAD Canada has these parts in stock to send them fast... I'm tired of waiting for my S300
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Old 11th May 2009, 11:27 PM   #20
HFERRAO is offline HFERRAO  Portugal
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Rui
boa noite
Comprei um NAD S300 também com o canal esquerdo "morto", aparentemente não tem nada queimado, esteve no representante mas a reparação seria da ordem dos 800€, segundo o anterior proprietário, pergunto se não tem o esquema que me possa enviar.
obrigado,
Henriques Ferrão
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