NAD C521BEE cd player no disc error - diyAudio
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Old 18th October 2012, 11:27 AM   #1
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Default NAD C521BEE cd player no disc error

Hi guys,

i bought a NAD C521BEE cd player second hand in mint condition but like the other NAD cd players i'm getting the no disc error both with cdr's and original pressed cds.

It's not happening every day but it's very annoying.
I have tried not switching it off with cd in the tray, powering it off and on to clear the error;sometimes does the trick others not.
I have read that the problem might be in the laser focus etc.

I was thinking of replacing the laser mechanism:
Nad C521Bee Laser Assy - Brand new spare part 5703120225050 | eBay

but i wonder if there is any other solution before replacing such a sensitive part.

BTW, the player sounds great when it's working

Any ideas?
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Old 18th October 2012, 11:41 AM   #2
Mooly is offline Mooly  United Kingdom
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Non technical version
Looks like a KSSxxx type pickup. Good chance it will fix it (remember to remove shorting solder blob if it has it) after fitting.

Technical version
You should really look at the RF signal on a scope first before condeming any pickup and make sure all mechanical matters are attended to such as the sled assembly. Spindle motors can fail and condition can be gauged by looking at the "noise" from the commutator on a scope. Check bearing for wear. Measure current draw of motor.

Pickups are favourite though.
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Old 18th October 2012, 11:52 AM   #3
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Quote:
Originally Posted by Mooly View Post
Non technical version
Looks like a KSSxxx type pickup. Good chance it will fix it (remember to remove shorting solder blob if it has it) after fitting.

Technical version
You should really look at the RF signal on a scope first before condeming any pickup and make sure all mechanical matters are attended to such as the sled assembly. Spindle motors can fail and condition can be gauged by looking at the "noise" from the commutator on a scope. Check bearing for wear. Measure current draw of motor.

Pickups are favourite though.
Can you explain more the technical version please?
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Old 18th October 2012, 12:05 PM   #4
Mooly is offline Mooly  United Kingdom
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Do you have scope of at least 10Mhz bandwidth ?

You measure the RF (eye pattern) from the pickups RF amplifier and look at the amplitude and "quality" of the recovered signal. Normally a CD should give around 1.2 to 1.5 volts peak to peak and the signal should be clean and well defined. Checking DC motors with a scope to evaluate problems is an old enginners trick and requires experience to interpret the results.

To do any real work on a CD player needs a good scope. This is how the RF signal should look. Correct ground points for the scope are essential to get a clean signal,

cd eye pattern - Bing Images
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Old 18th October 2012, 12:25 PM   #5
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Quote:
Originally Posted by Mooly View Post
Do you have scope of at least 10Mhz bandwidth ?

You measure the RF (eye pattern) from the pickups RF amplifier and look at the amplitude and "quality" of the recovered signal. Normally a CD should give around 1.2 to 1.5 volts peak to peak and the signal should be clean and well defined. Checking DC motors with a scope to evaluate problems is an old enginners trick and requires experience to interpret the results.

To do any real work on a CD player needs a good scope. This is how the RF signal should look. Correct ground points for the scope are essential to get a clean signal,

cd eye pattern - Bing Images
I have a Fluke scope.
I think you are talking about the RF pattern testing as decribed in the Nad's service manual.
-It says to use the Sony Test CD YEDS-7 but i dont have such cd.
-If the waveform is not in best shape can i adjust it and how?
-Are you saying that the no disc error is from a bad waveform?
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Old 18th October 2012, 12:52 PM   #6
Mooly is offline Mooly  United Kingdom
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The actual CD makes no difference to the pattern of the waveform as there are only two. Normal play mode on a track is one and the other is the brief inter track space. Its the same for any disc.

The YED's series of discs are made to high tolerance and known characteristics such as reflectivity. In practice 99% of commercial red book standard discs give the same result. Occasionally you can have a disc of low reflectivity but if you try a couple and they give similar results then your good to go.

Whether the RF can be improved depends on the player and its adjustments but I wouldn't advise altering anything without knowing what you are doing and certainly not without marking with ink the presets original position. Tracking and focus gain make no difference to RF quality. Focus bias does and EF balance is one of the most critical. Sometimes the names used vary a bit. Tracking gain can be set by looking for a low frequency "fundamental" appear in the tracking error waveform as the gain is increased. You back the gain off until this just disappears.

9 time out of 10 the problem is the pickup though, whether it be contaminated internal optics, lens suspension issues or some combination.
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Old 18th October 2012, 12:58 PM   #7
Mooly is offline Mooly  United Kingdom
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You might find this interesting. Look for anatechs and my posts,
whining kss210A after replacement
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Old 15th November 2012, 05:56 PM   #8
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I bought the Cambridge Audio D500 SE and i feel more happy now:
Cambridge Audio D-500SE [English]

What do you think?
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Old 15th November 2012, 06:04 PM   #9
Mooly is offline Mooly  United Kingdom
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It looks fine and gets a good write up but its what its like in reality that matters

Pleased you like it anyhow.
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