I tested powering on both of my CDX chassis disconnected from everything else.  I would have thought that without any connections to the switches or control panel, the motor would not spin the platter. But in both units, the platter starts turning. 

Here is the service manual schematic for the motor stop. The laser switch in my test is disconnected.  With power on the CDX, I measure 12 VDC between the two pins the switch closes.

In looking at the schematic and with the Laser Switch connector out, 63-2 and 63-1 are open.  I thought that would prevent the motor from turning.  With that connection off, I measure -5.8 to -6 VDC at 63-2 and +6 to +8 VDC at 63-1.  The closing of the door will close the Laser Switch which joins those two voltage points. So with it open, the motor should not spin, right?  I must be missing something here though...because both units measure the same here and behave the same.

Sounds very much like a rivet via fault or a cracked solder joint in the power supply area.
It can sometimes be difficult to guess at what will happen in a circuit if one or more ground points are disconnected.

Martin

I'll have to just dig in deeper. I did measure some various signals and with nothing connected to the main chassis, I see a +6 VDC on the DO signal which is the state of the signal in Play mode. With everything disconnected, I would expect that signal to be low (not in Play mode). 

Can you tell me if the platter motor should be off if the CDX main chassis is turned on by itself (no connections to the lid motor control board or control & display board)?  If the connector for the laser switch inputs is removed, should a working CDX power up with the motor not running? 

I agree with Martin John. And please do those ominous griplets. They are responsible for the strangest issues - from degraded or crackling audio to odd servo problems.

When you press PLAY, the motor will indeed turn immediately as the player is looking for the TOC. It will stop only if no CD is detected by the laser.

I say, do the solder job! 😂

I'm not sure what to make of this yet (will have to sleep on it) but I was able to manually coax the CDX into working. I suspected part of the problem is in the initialization of the laser head and the other logic that controls the motor.  When the CDX is failing, the platter immediately starts spinning and I can see some up an down movement on the laser head (light pen?).  To be able to put a CD in place, I have to disconnect power, open the door, insert the CD, then close the door.  After that I can turn power on. At this point the CDX tries to read the CD, detects nothing and briefly displays a question mark. I began running these tests with the bottom of the CDX case removed.  I have to add some support underneath so the laser mechanism isn't obstructed. This allows me to see what is going on since I have to have the lid in place to hold down the CD.  I was able to see that the laser head wasn't moving.  So I helped it along a little and that reset something.  The motor came to a stop.  I pressed play but the CDX didn't go into play mode. The motor also didn't turn. I have seen that before and it usually meant the worm gear controlling the door closed position needs adjusting. I did that, tried the play button as I adjusted and the CDX began playing.  I ran through a few tracks then tried a test of ejecting the CD and reinserting it.  That worked fine.  The next test was to turn power off the CDX, then back on.  I did that and the CDX started up okay.

The CDX is not fixed of course.  I have been here before.  When I had the CDX working a couple of nights ago it went through this same scenario where all of a sudden it got into the correct mode where it came up with the motor not turning and the laser head adjusting correctly to a CD. 

Maybe there is a problem with the laser head control. Something in the timing of things during start up? Could the laser sometimes stop in a position it can't start correctly from?  Is the problem a mechanical adjustment problem on the laser head?

One of my next steps is to repeat the test tomorrow with the same CDX chassis I got working tonight.  Then try the other CDX chassis and see if the same coaxing can get it playing again.  I know it also works because I also had it playing a CD a few days ago. 

chartz wrote:

I agree with Martin John. And please do those ominous griplets. They are responsible for the strangest issues - from degraded or crackling audio to odd servo problems.

When you press PLAY, the motor will indeed turn immediately as the player is looking for the TOC. It will stop only if no CD is detected by the laser.

I say, do the solder job! 😂

In one of my earlier posts in this thread I mentioned that I had reworked the griplets on the two boards of my first CDX unit. That didn't help.

Regarding the start up - Keep in mind, the motor starts turning with the CDX door open.  I don't think it should do that.  You can't insert a CD with the motor spinning.  When I have got the CDX into working mode, I can see the unit start with the motor not turning.  To help trouble-shoot the problem, I expected the CDX to start with the motor not turning if I turned it on with no cables connected (to the door motor, laser switch, load switch, control and display panel).  If none of those things are present, I would expect the motor to not start and the laser head not to look for anything.  That doesn't appear to be the case though as both of my CDX units behave the same.

If it moves the laser lens up and down to seek focus, the lid contacts or related circuit is not working correctly.

Martin