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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Nikko NCD-730 CD-Player Repair
Hi All, all input will be greatly appreciated.
Symptoms: 1. Tray will not eject if its empty. Works fine if there is a CD present. 2. Will not read directory or spin-up when a CD is inserted and the unit is in its normal horizontal position. However, if the unit is in any vertical orientation, it plays fine. After the unit is playing, it cannot be tipped back to horizontal. Observations: 1. Motor Resistances: Spindle 12 ohms, Sled 12 ohms and Tray 16 ohms 2. Motor Voltages: Spindle 3.5V Start/0.6V Run, Sled 5V Track-To-Track Max./0.6V Run and Tray 3.5V Max. 3. Test Point Voltages: Track 0-5 mV Horizontal and Vertical, Focus 150mV Vertical and 350mV Horizontal. This is related only to the tray orientation not the entire unit. 4. If I manually lift the clamping magnet then the tray ejects without a CD present. Corrective Actions: 1. Flipped the poles of the clamping magnet and now the unit's ejection system works properly. 2. Adjusted the Focus Gain to 30 mV Vertical which results in 180 mv Horizontal (no further adjustment is possible). The unit continues to play properly vertically and now can be layed down to horizontal and continue to play properly. However, the unit will still not read directory or spin-up from horizontal starting position. Question: What will cause the significant Focus voltage variation from horizontal to vertical orientation? TIA |
#2
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A few wild guesses...
Clamping magnet is so strong that the load/eject drive can't overcome it's grip. This was a problem in some Onkyos, the remedy was an adhesive spacer sheet to separate the chucking pieces. With a disc present, the magnet and its companion are separated by the CD itself. I've seen some units focus only when sideways or upside down. Trouble was in pickup which had "sagging optics" requiring more voltage to lift into focus. Maybe you could fudge it a little by lowering the disc table height. Good Luck, Doug |
#3
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Hi Doug, thanks for your help. Unfortunately, upon lowering the platter
to the height required to reliablely mount the CDs then they would mess up on the outer tracks. Therefore, I bit the bullet and removed the lens actuation cover and flipped the suspension springs upside down. Now the unit works like new... Thanks again! Doug wrote: A few wild guesses... Clamping magnet is so strong that the load/eject drive can't overcome it's grip. This was a problem in some Onkyos, the remedy was an adhesive spacer sheet to separate the chucking pieces. With a disc present, the magnet and its companion are separated by the CD itself. I've seen some units focus only when sideways or upside down. Trouble was in pickup which had "sagging optics" requiring more voltage to lift into focus. Maybe you could fudge it a little by lowering the disc table height. Good Luck, Doug |
#4
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I never thought to try that. Very clever, and glad it's working.
Doug |
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