NAD 3225pe amplifier problem

daniloreyes · 6th January 2010, 04:03 AM

Hi,
I have a NAD amplifier and need help debugging it.

poynton · 6th January 2010, 05:15 AM

OK, I'm listening .....

.

daniloreyes · 6th January 2010, 06:26 AM

Sorry I had to wait until thread was aproved.

The c511 was damaged and I replaced it (radio shack .1 uf 50v

) also noticed the fuses were blown. but replacing them did nothing as they blew again. What and how should I proceed?

Thanks

daniloreyes · 6th January 2010, 06:28 AM

Also I'm in need to learn to repair. so I want to to this DIY way!

I measured the most of the diodes, seem ok (620-640ohms one, way none the other)
How do I measure the transistors as they seem to be the problem?

daniloreyes · 6th January 2010, 06:33 AM

The Q503 and q504 have big heat sinks

daniloreyes · 6th January 2010, 06:35 AM

Oh and the symtoms are high distortion, low volume.

Mooly · 6th January 2010, 07:14 AM

That's the PSU you have posted.... maybe it's a bit early in the morning lol... it's a bit odd.
Which fuses are blowing ?
Do they blow with no speakers connected ?

It looks like the amp runs on a high stabilised supply with a lower higher current supply to "take over" if the output increases beyond a certain point.

Most amp faults see the output transistors fail... either as "just" that or with other damage.
You need to put a mains filament bulb of say 100 watts in series with the incoming supply to allow you to work on it non destructively.

poynton · 6th January 2010, 07:30 AM

Which fuses blow F501, F502, F503, F504 ??

daniloreyes · 6th January 2010, 01:31 PM

There is a switch that allows for 4 ohm or 8 ohm operation. All fuses where blown, as I tried changing the position while debuggin.
How ever after reolacing the c501 and fuses, I left the switch on the 8 ohm position and only f503 and 504 blew.

daniloreyes · 02:09 PM

I'm trying to add a better shematic view with no luck. also I have to wait for approval on postings. is there a post limit to be able to post inmediatly or something?

Where do I connect the 100 watt bulb ?
the speakers where installed when this happened.

6th January 2010, 04:03 AM	#1
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	NAD 3225pe amplifier problem Hi, I have a NAD amplifier and need help debugging it.

6th January 2010, 05:15 AM	#2
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	OK, I'm listening ..... . __________________ If it ain't broke, break it !! Then fix it again. It's called DIY !

6th January 2010, 07:30 AM	#8
poynton Magneto the Gravity Man diyAudio Member Join Date: Mar 2005 Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)	Which fuses blow F501, F502, F503, F504 ?? __________________ If it ain't broke, break it !! Then fix it again. It's called DIY !

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6th January 2010, 06:26 AM	#3
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	Sorry I had to wait until thread was aproved. The c511 was damaged and I replaced it (radio shack .1 uf 50v ) also noticed the fuses were blown. but replacing them did nothing as they blew again. What and how should I proceed? Thanks

6th January 2010, 06:28 AM	#4
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	Also I'm in need to learn to repair. so I want to to this DIY way! I measured the most of the diodes, seem ok (620-640ohms one, way none the other) How do I measure the transistors as they seem to be the problem?

6th January 2010, 06:33 AM	#5
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	The Q503 and q504 have big heat sinks

6th January 2010, 06:35 AM	#6
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	Oh and the symtoms are high distortion, low volume.

6th January 2010, 07:14 AM	#7
Mooly diyAudio Member Join Date: Sep 2007	That's the PSU you have posted.... maybe it's a bit early in the morning lol... it's a bit odd. Which fuses are blowing ? Do they blow with no speakers connected ? It looks like the amp runs on a high stabilised supply with a lower higher current supply to "take over" if the output increases beyond a certain point. Most amp faults see the output transistors fail... either as "just" that or with other damage. You need to put a mains filament bulb of say 100 watts in series with the incoming supply to allow you to work on it non destructively.

6th January 2010, 01:31 PM	#9
daniloreyes diyAudio Member Join Date: Jan 2010 Location: OR	There is a switch that allows for 4 ohm or 8 ohm operation. All fuses where blown, as I tried changing the position while debuggin. How ever after reolacing the c501 and fuses, I left the switch on the 8 ohm position and only f503 and 504 blew.

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