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Static charge damage to NAD 5240...any fix?

J English

J English

Super Member
Looking for advice on where to start with one of my favorite old players, a NAD 5240. Very basic cd player from 1987, but has a very nice sound. I'd like to fix it if I can.

I was using it with one of my small 3116 chip amp builds. That amp has a volume pot I added that had, stupidly, an all-metal turn knob. I must have built up a static charge crossing the rug, because I got a large pop when I touched the volume knob. I believe at the time, the display actually flickered and died, then came back. My main fear at the time was for my recently-restored KEF 15.2 speakers, but they came through fine. I think the amp is OK too (I removed the stupid knob right away) but I have not given it a full check yet. It's still in the "time out" corner.

The NAD has distorted sound now. Sound on both channels, decent output, but sound is grainy and slightly distorted when amplified. When I listen to a classical CD via the RCA outputs to a headphone, at the low native device output, it sounds almost normal. The display is normal and working. So, whatever took the hit internally seems to have been only SLIGHTLY affected, but just enough to distort.

Fair number of chips on the main board, so if one of those is what was hit, I assume I'm SOL. With a small charge like that, is it possible that any of the components that I can replace (caps, etc.) could be the issue?

I can probably sell her off for parts if all else fails, but wanted to see if anyone else has faced something like this. Thanks for any advice!
 
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Unless you have the specialized test equipment and the probes to go with it you are in real trouble. Go you the YouTube channel TRX Bench ( https://www.youtube.com/user/TRXBench } the presenter shows in detail how he DX's problems. I was looking at the going rate for a NAD 5240 unless you can fix it yourself it is not worth repairing given the cost of bench time.
 
If it were me I would localize the problem as best I could (find what still works right, what doesn't) and use schematics to trace out signal path. Gonna take some patience. Probably a chip or two was struck, yes. I have encountered op-amps that half work and the sound is distorted.

Then work from output stage backward, replacing one thing at a time until the problem goes away.

The transport still sounds like it survived, so thats something
 
Does it have SPDIF out you could feed into a DAC? That would allow you to determine if the fault is in the reading side, or the DAC onwards.
 
cpt_paranoia said:
Does it have SPDIF out you could feed into a DAC? That would allow you to determine if the fault is in the reading side, or the DAC onwards.
Click to expand...
Akin to that, burning a CD of a 100hz sine wave and looking at the output on a scope or even a line in on a computer with a program which you can see the wave might determine how healthy the DAC is if not the output amps.
 
Hello!
If you don't have already you can download the service manual from electrotanya!
You have (as per service manual) 2 outputs. One fixed output and one variable output! both have tha same issue?
 
dimanag said:
If so check the voltage on q511!
Chack with your dmm between pin 4 and 8! what volage do you have?
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5 years later I am having a similar issue with loud static when I play a CD in a NAD 5240.

Voltage at Q511 between 4 and 8 is 9.97v. Any ideas what this means? Dimanag - help! :D
 
Hey, Doctor Fuse - I still have my NAD, had recently pulled out again to junk, sell or rehab. This was my old thread.

When I measure my Q511 voltage, I get 9.92v between those pins. Very close to what you got. I get the "degraded" sound on both fixed and variable outputs.

Dimanag, any further advice for us with this Q511 result?
 
Thanks, super helpful information by message. Will attempt to diagnose if it's the DAC chip or the op-amp that took the static charge. If just the op-amp, fixable. If the DAC chip, she's a goner...
 
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