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

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

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

I never thought to try that. Very clever, and glad it's working.

Doug