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Old 30th June 2012, 02:21 PM   #1
ClassA is offline ClassA  Taiwan
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Default quad 67cd noise from CD transport

Hi,
There is a loud noise generated by quad 67cd transport when disc is playing. The noise frequency is higher in the first song than the last song in a disc. Could anyone tell me what the root cause is? CDM9 laser pick-up degradation?

Cheers
David
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Old 30th June 2012, 06:56 PM   #2
Mooly is online now Mooly  United Kingdom
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How loud is loud ?

I'm not really familiar with CDM9 but possible causes of noise would be the focus coils in the pickup and possibly noise from the motor due to AC being present and exciting the windings. Now you say the noise varies from 1'st to last tracks and that ties in with the motor which slows as the disc plays (due to CLV or constant linear velocity). It runs faster at disc start than at the end.

I don't know what type of motor is used (DC or Hall effect) but it might be worth looking at the motor drive voltage on a scope to make sure no excess noise and hash is present. It could be something like a failed cap in the servo motor servo circuit.

The same applies to the focus coil and its drive.

The radial tracking (for the swing arm) I wouldn't have thought would vary with disc position although they can emit a characteristic hf noise when track searching.
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