My observation of several Sony “KSS” style optical pickups is that the very top of the lens should rise just slightly above the black plastic housing which encloses the focus/tracking actuator while playing a disc. View this from the side (edge) of a disc which is playing. You will need to remove the disc tray and operate the “bare transport” using a magnetic clamp.
I’m not familiar with the Nakamichi CD4. Does it have a magnetic disc clamp? Is it possible for you to post photos of the transport mechanism in your CD player?
Also watch the movement of the lens (from the side) as the player performs a focus search without a disc. The lens will first move down below the top of the actuator housing and then will rise up until the top of the lens is about 2 to 4mm above the actuator housing. When playing a disc the lens height should be centered between the low and high extreme of lens movement which occurs during focus search without a disc.
The proper “working distance” between the top of the lens and the disc surface should be the same for all KSS-150A optical pickups. No matter what the brand/model of the CD player is.
I’m currently working my way through a bunch of CD players which use the KSS-240A. As I do this I’ll post my measurements of disc height. Note that the KSS-150A may require a slightly different disc height than the KSS-240A.
-EB
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I viewed your scope traces. The RF amplitude should not vary that much as the disc rotates. This indicates you don’t have sufficient gain for the focus or tracking servo (or both).
What is the position of the focus gain trimpot?
Also what is the position of the tracking gain trimpot?
Usually 50% for both focus and tracking gain is a good starting point.
In fact I’ve read service manuals which state “adjust both tracking and focus gain trimpots to 50%” after replacing the optical pickup.
Next you could try increasing the focus gain and that should reduce the cyclic variation in RF signal amplitude. If you raise the focus gain too high then you will hear a hissing sound from the optical pickup itself.
Repeat this with the tracking gain trimpot.
In another post a diyAudio member stated that an experienced technician can adjust the focus and tracking gains by listening to the hissing sound from the pickup itself.
The last 5 CD players on my workbench had very stable RF amplitudes which did not vary at the rotation speed of the disc. This was the case even when playing discs with considerable warp. While playing a warped disc I could see the lens moving up and down as much as 1-2mm as the disc rotated when playing the highest numbered track near the outside edge of the disc. Yet the RF amplitude was quite stable.
Note: Philips CD players with swing-arm pickups don’t have trimpots for adjusting focus or tracking gain. But most Japanese CD players do have tracking and focus gain trimpots.
-EB
Often the best way to set EF BAL is to play a disc and then press PAUSE button. View the tracking error signal with oscilloscope. There should be a large pulse of the tracking signal once per disc revolution when the MCU commands the servo to jump back while in pause mode. The top and bottom of this “jump” pulse should be equal above and below the baseline. Other posts on diyAudio will provide more detail. Search for “tracking adjustment.”
-EB
Reviving this thread since I'm in the same boat with a player that starts to spin and doesn't go any further. I've seen a few accounts of the CDP-4 and CD Player 4 doing this. The original poster did a fantastic job of going through the diagnostic steps and perhaps I can do the same but it's a lot to tackle. Since then, is there any consensus on the idea that CXA1082BS is just a bad egg? I can order one, replace it and see what happens like a caveman. Not like I haven't already replaced all of the blue Panasonic caps and the one leaky 15uF / 16v that I sure hoped would bring it to life... Any recommendations / updates / experience?
Thanks!
Thomas
Thanks!
Thomas