NAD 7250PE Intermittent Distortion

nbenford · 24th April 2004, 11:57 PM

Hello,

I've been trying to get to the bottom of the problem with my NAD 7250PE receiver. The right channel (only) often lapses into a strange distortion where the channel all but drops out with the main musical "hits" straining through. I replaced the 4 main big filter caps, which seemed to help, but the problem is still occuring, albeit less frequently. Of course, it could just be luck that it hasn't happened as much, but the old caps looked worse for wear anyway.

It would make sense that it is a transistor (it sounds like a switch being turned on and off very quickly at the loudest current spikes) but I do not have the schematics for this model. Does anyone know the location of the possibly problematic transistor, or at least the location of the bias pot, which could also be causing this problem? Apart from this problem, I'm quite enjoying the sound of this unit.

Cheers,
Noel

planet10 · 25th April 2004, 08:11 AM

Is the soft clipping turned on?

dave

soma · 26th April 2004, 06:25 AM

You can remove right channel Q501(2SK363) or changed D501 from 1S1588 to 10meg resistor.Maybe can solved this problem.

nbenford · 27th April 2004, 08:01 PM

The soft clipping does not seem to effect the distortion.

Soma, I'll give that a try, thanks!

Cheers,
Noel

eLarson · 29th April 2004, 03:10 PM

Some other, even simpler things to check:

Have you tried reconnecting your cables (dirty connection somewhere)?

Is your volume control or balance control dirty (noise when it is turned)? This one afflicted my parents' 7250PE.

Erik

nbenford · 1st May 2004, 09:08 PM

The distortion appears on every input, so I don't believe that it is a dirty connection. It happens to phono, aux, cd, video, etc... Also, the volume and pan pots do not crackle when I turn them, so they seem fine.

Thanks!

Noel

24th April 2004, 11:57 PM	#1
nbenford diyAudio Member Join Date: Apr 2004 Location: Brooklyn, NY	NAD 7250PE Intermittent Distortion Hello, I've been trying to get to the bottom of the problem with my NAD 7250PE receiver. The right channel (only) often lapses into a strange distortion where the channel all but drops out with the main musical "hits" straining through. I replaced the 4 main big filter caps, which seemed to help, but the problem is still occuring, albeit less frequently. Of course, it could just be luck that it hasn't happened as much, but the old caps looked worse for wear anyway. It would make sense that it is a transistor (it sounds like a switch being turned on and off very quickly at the loudest current spikes) but I do not have the schematics for this model. Does anyone know the location of the possibly problematic transistor, or at least the location of the bias pot, which could also be causing this problem? Apart from this problem, I'm quite enjoying the sound of this unit. Cheers, Noel

25th April 2004, 08:11 AM	#2
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	Re: NAD 7250PE Intermittent Distortion Is the soft clipping turned on? dave __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

29th April 2004, 03:10 PM	#5
eLarson diyAudio Member Join Date: Aug 2002 Location: Gaithersburg, MD	Some other, even simpler things to check: Have you tried reconnecting your cables (dirty connection somewhere)? Is your volume control or balance control dirty (noise when it is turned)? This one afflicted my parents' 7250PE. Erik __________________ Would a woodchuck bother to chuck MDF?

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26th April 2004, 06:25 AM	#3
soma diyAudio Member Join Date: Apr 2004 Location: nanjing	You can remove right channel Q501(2SK363) or changed D501 from 1S1588 to 10meg resistor.Maybe can solved this problem.

27th April 2004, 08:01 PM	#4
nbenford diyAudio Member Join Date: Apr 2004 Location: Brooklyn, NY	The soft clipping does not seem to effect the distortion. Soma, I'll give that a try, thanks! Cheers, Noel

1st May 2004, 09:08 PM	#6
nbenford diyAudio Member Join Date: Apr 2004 Location: Brooklyn, NY	The distortion appears on every input, so I don't believe that it is a dirty connection. It happens to phono, aux, cd, video, etc... Also, the volume and pan pots do not crackle when I turn them, so they seem fine. Thanks! Noel

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