Another NAD 7240PE repair thread

[Kodiak2]

Hi Folks,
Chanced my way into a NAD 7240PE on Facebook Marketplace for $25. Basic function worked as is, but all of the pots were noisy, so I resolved that first and hoped for the best.

Cleaning up all of the pots (twice), and removing 30 years of nicotine from the surfaces of the boards etc helped a lot but I still have an issue with a scratchy / fuzzy sound on one channel that sounds along with the beat.

I did notice some failed/prefailed power supply capacitors when I took it apart, but didn't want to dig deeper into doing a capacitor replacement unless that seems like a likely reason for the scratchy / fuzzy sound.

I'm quite a novice with hi-fi stuff, but have ample technical experience so I should be able to make sense of any advice folks might have about the likelihood of capacitors causing this sound.

I dug through a few threads here and on other forums prior to posting but nobody seems to be describing my specific problem in the NAD repair threads I've found.

Thanks!

 

[OldJBL]

I am not able to give you advice in a deep technical sense but the first thing I do to diagnose a problem is to bypass the amp section buy hooking up a known working amp via the pre-out connections. If everything works in the tuner and pre-amp areas then the problem is very likely in the amp section. The tuner and pre-amp sections worked fine with 7400 and 7100 receivers I bought knowingly needing repair when hooked to a Denon 750. Then when a technician looked at them the 7400 needed transistors replaced for one channel in the amp section and the 7100 had solder breaks in its amp section. Testing the tuner and pre-amp using a known working amp saved a lot of time diagnosing the problems.

 

[Johnny_Law]

Agreeing w/ @OldJBL and can add that I've had bad PS components (in my case, a resistor) cause the same symptom you describe. It took me a LOT of head scratching to figure it out (here).