Hi, any ideas on the following? tried what I could but no results...
A friend asked me if I could repair a NAD CD player 514. When you inserted a CD, it briefly started spinning but then jumped to a state where the track and time indicators are hyphens ("- - - -").
1 I checked the lens and everything around it, couldn't find anything. I found I could by the complete lens unit for $15 or something so replaced. Alas, no improvement.
2 I checked the connections from the board to the drive unit, resoldered a few, no improvement. During this process, I think I might have short-circuited the power to the drive motor.
3 I took the transistor pairs which are driving the motor out, couldn't find a problem but replaced them nonetheless. No result.
4 I replaced the large motor management IC BA6109 but again, no result
Power to the part of the PCB where the motor management is located is OK. All resistors and inductors seem to be OK. I really am at a loss here.
Any suggestions?
A friend asked me if I could repair a NAD CD player 514. When you inserted a CD, it briefly started spinning but then jumped to a state where the track and time indicators are hyphens ("- - - -").
1 I checked the lens and everything around it, couldn't find anything. I found I could by the complete lens unit for $15 or something so replaced. Alas, no improvement.
2 I checked the connections from the board to the drive unit, resoldered a few, no improvement. During this process, I think I might have short-circuited the power to the drive motor.
3 I took the transistor pairs which are driving the motor out, couldn't find a problem but replaced them nonetheless. No result.
4 I replaced the large motor management IC BA6109 but again, no result
Power to the part of the PCB where the motor management is located is OK. All resistors and inductors seem to be OK. I really am at a loss here.
Any suggestions?
If this is a common KSS type pickup then did you remove the static protection shorting link (typically a solder blob)?
If you have shorted something out then all bets are off.
If you have shorted something out then all bets are off.
No I did not remove such blob ;-) I’ll check later tonight! (No cluenwhere the blob is but I’ll see) - thanks
Not yet
Alas! I tried just now (couldn't find the time earlier), found the blob, undid the connection, and tried. Regrettably, it takes in the CD, I hit start, the display shows ">" but after a few seconds changes to "- - : - -". However I noticed a sound coming from the lens positioning motor, just before it changes to "- - : - -". Out of frustration, I gave the CD a spin with my hand. It resisted but then started spinning the CD! only to change into "- - : - -" after one or two seconds. This must however mean the spinning motor and drivers are intact. It seems it somehow "thinks" there is no CD. Any thoughts?
Alas! I tried just now (couldn't find the time earlier), found the blob, undid the connection, and tried. Regrettably, it takes in the CD, I hit start, the display shows ">" but after a few seconds changes to "- - : - -". However I noticed a sound coming from the lens positioning motor, just before it changes to "- - : - -". Out of frustration, I gave the CD a spin with my hand. It resisted but then started spinning the CD! only to change into "- - : - -" after one or two seconds. This must however mean the spinning motor and drivers are intact. It seems it somehow "thinks" there is no CD. Any thoughts?
There could be many possible causes...
A couple of quick basic tests are to confirm that the sled will return to the correct rest position if it is first manually moved toward the outer edge of the disc. Do that with the power off, then when you power up and open and close the tray the sled should return to the correct position. At that point the lens should perform the focus search routine and move up and down 3 times.
Spindle motors can give trouble generally. A quick bodge can be to disconnect it from the circuit and then apply a 9 volt battery to spin it up to a zillion miles an hour. Reverse polarity and do it again. That cleans up deposits on the commutator.
If it passes all those tests then you are getting into more serious diagnostics and scope territory.
A couple of quick basic tests are to confirm that the sled will return to the correct rest position if it is first manually moved toward the outer edge of the disc. Do that with the power off, then when you power up and open and close the tray the sled should return to the correct position. At that point the lens should perform the focus search routine and move up and down 3 times.
Spindle motors can give trouble generally. A quick bodge can be to disconnect it from the circuit and then apply a 9 volt battery to spin it up to a zillion miles an hour. Reverse polarity and do it again. That cleans up deposits on the commutator.
If it passes all those tests then you are getting into more serious diagnostics and scope territory.
All CD mechanisms are controlled by a system controller looking for the correct vital signs;
Insert disc, the laser assembly will return to the TOC position, (inside most point before track 1 of the CD). The laser will light. If focus is achieved the spindle motor will spin. Any other error is down to read and errors from the laser, (either caused by faulty/noisy signal from the laser or power supply noise/failure). System board failure is uncommon.
If any of those points fail, the system controller will return to the no disc message and stop. In the worst scenario it will stop the tray from opening, to retrieve the inserted CD.
Insert disc, the laser assembly will return to the TOC position, (inside most point before track 1 of the CD). The laser will light. If focus is achieved the spindle motor will spin. Any other error is down to read and errors from the laser, (either caused by faulty/noisy signal from the laser or power supply noise/failure). System board failure is uncommon.
If any of those points fail, the system controller will return to the no disc message and stop. In the worst scenario it will stop the tray from opening, to retrieve the inserted CD.
Thanks you all! I found the service manual and schematics. There is a trouble shooting / fault tree in the manual. I'll use it. It points to either the power to the optical unit or the transistors driving the lens movement, as far as I can tell now.
Does anyone have a tip on how to check if the laser is illuminated? the disc is in the way... or can I simply see it in the dark?
Does anyone have a tip on how to check if the laser is illuminated? the disc is in the way... or can I simply see it in the dark?
Turn off power, place a piece of thin paper over the lens assembly and when you power it up, the laser will be come visible as a red dot in subdued lighting.
DO NOT look directly into the beam!
DO NOT look directly into the beam!
The laser lights only during the time of the focus search operation when the lens is moving up and down.
The light can be very dull to the eye but that doesn't mean its not bright, its just that our eyes can not see the near infra red wavelength very well.
The light can be very dull to the eye but that doesn't mean its not bright, its just that our eyes can not see the near infra red wavelength very well.
It's really resisting repair! Yes the laser lights but it does not focus, I mean the lens is not moving. I removed the plastic protective cover and found out the 'new' pickup unit is actually not in a very good shape, the connecting strip looks rusted or weathered. Now I checked the voltages of the transistors driving the tracking mechanism. There are 2, one labeled FOD, the other TRD. FOD does change, from 0V quickly up or down, to fast for my multimeter to display but it changes, some volts. TRD does nothing. The lens however does not move. I disconnected the connector at the pickup side, sprayed it with contact fluid and reconnected (I even put the 'antistatic blob' back for this operation). Laser still working but no coil movement. I am beginning to suspect the pickup unit. Any suggestions on how I can test it?
Try measuring the continuity of the focus coil... it works just like a speaker coil in a magnetic field.
I would also imagine that a DVM on the diode range might have enough current to actually move the lens. You should be able to do this test with it all in circuit. Just switch the player off and check the resistance from FOD to ground. That should be the coil resistance. Now try the meter on diode range and see if the lens moves.
You can do the same test on the tracking coil as well.
I would also imagine that a DVM on the diode range might have enough current to actually move the lens. You should be able to do this test with it all in circuit. Just switch the player off and check the resistance from FOD to ground. That should be the coil resistance. Now try the meter on diode range and see if the lens moves.
You can do the same test on the tracking coil as well.
It’s all quite puzzling: I found out that one of the coils was not properly connected, because of the crappy flexible print in the lensunit, I bypassed it, now the connections, measured from the connector which connects to the main board, were OK, I tried and it worked! But only for about 1 minute! Now, if I put in a CD, it starts spinning, recognizes the CD, shows total length etc. in the display, but stops afterless than a minute. My gueass is the lens unit is poor quality. I tried the old one but that one has another problem. I decided to give up (very hard decision).
You've done well finding the break and proving there was a problem there but it does sound a bit like that pickup has other issues if it still won't play 100% correctly. The 'rust' you mentioned earlier could mean the optics have been affected by damp/condensation.
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