Technics SL-PD627 CD Changer Problem

[braunerf18]

Hi all,

I recently purchased a Technics SL-PD627 CD Changer in working order. After a few weeks I've run into an issue with the tray that I'm looking for some guidance with.

The tray will open no problem when I press the Open/Close button, however it will only close maybe 3/10 times when I press the same button. What's odd is if I press the "Play" button instead of open/close, it will close nearly every time.

When I try to close it while watching with the cover off, I see the main motor move just a bit, then stop. Again, if I push play, it will close no problem. I took off the drive belt and wound it tightly with a rubber band instead and this seems to have helped a bit. The tray definitely opens/closes far more gently with the rubber band, however closing is still intermittent.

This leads me to believe the motor should be fine and that it may or may not simply be a drive belt issue. I do find it odd that it will work when I press Play instead of Close, so I'm not sure what's going on there.

Thanks in advance for your help.

 

[braunerf18]

Any ideas?

 

[Rod Bond]

Does anyone out there know how to fix this issue? I purchased this CD player a couple days ago and am having the same problem, the 'open/close' button won't close the tray all the way but the 'play' button will for some reason.

 

[Fred S]

I'm a bit late to this thread, but I'm having similar flaky behavior with the drawer. For a while I had to help it all the way closed in order to make the unit start playing. Now the drawer doesn't respond at all. When I power the system on it'll close, then it'll open back up again.

I found the service manual online (and can share it, but it's too big to attach here). I've also had the unit apart and given it a thorough cleaning.

The drawer mechanism on this thing uses an interrupted gear to allow one motor to open/close the drawer, raise and lower the CD player, and also open/close the drawer by a second method when a disk is playing. It's very clever, and I spent hours figuring out how it works.

I recommend not taking the gear train apart or removing the drawer unless you have the service manual. Re-timing the gears and drawer is critical. I attached the details on gear train timing in case anyone needs them. If you just want to swap the belt out, you can do that by removing the turntable from the tray.

There are two switches that detect the drawer position. Under the large gear is a two way rocker switch that is activated by the rotation of the gear. It's visible in the background of this image. It can be seen through the square hole when the hole is in the 6 oclock position. There's also a small contact switch to the left of the drawer's drive motor, which is what the above image shows. It's got a clear housing and looks like a LED or optical sensor, but it's actually a reed switch. I suspect that mine is going bad, the resistance varies between 8 and 60 ohms. I haven't had any luck finding a replacement, and it's too small to take apart for cleaning. I gave it a Deoxit soak, but it didn't really help.




The reed switch is closed when the drawer is all the way open. The and using the rocker switch it's able to determine what state the gear train is in. And it knows if it's playing a CD or not. It's able to combine all of that data to determine which method it should use to open the drawer.

I think that the variable resistance of this switch is causing the unit to get confused, and try to open the drawer when it's already open.

I'm also going to throw a couple of drive belts at the drawer and turntable motors. The belts are only $12, so it's worth the risk. This system is almost entirely mechanical, and needs a decent amount of torque at the end of the drawer's travel to do things like lock the drawer open, lock the drawer closed, or raise the CD head. I think that the belt is slipping at these points, preventing the drawer from cycling completely.

If anyone finds a replacement for that clear limit switch, please let me know.

 

[Fred S]

SUCCESS!!!

I'm pleased to report that my player is working perfectly again. I ordered a pair of belts from WebSpareParts. They arrived in a little over a week, signature required.
As you can see from the attached images, the old belts had significant stretch. I'd witnessed my tray drive belt slipping, so I was expecting this. After all the belts are 30+ years old.


Tray drive belt. This is serious stretch on a belt that has to do a lot of work.


Turntable drive belt. Some stretch, but it's a low-torque application. I replaced it anyway.

My initial reassembly was a failure,. The tray closed and then immediately opened again. The Play button did nothing. The Disk Skip button made the tray act as though I was playing a disk. It would only let me access four of the disks, not all five.

It took me a while to figure out the trick. The manual shows the gear position for installing the tray. But it doesn't indicate the location of the pin that elevates the player head. I think that this is because it's assumed that you'll install the player head in a later step.

Because the player head wasn't shown, I was leaving its elevation pin on the lower deck of the gear. I should have had it on the ramp. The attached picture shows the correct location. The two gears at the top of the picture have triangles on them. I marked them in black for contrast. They must be in this position, with the player head elevation pin near the top of the elevation ramp, in order to install the tray.



Once the tray is on, it will move freely. That's OK. Make sure it slides in and out freely. Reconnect all of the ribbon cables, then close the tray by hand. It will lock closed. This is important, you must close the tray before turning the unit on.

Install the turntable.

With the tray closed, plug the unit in and power it on. The geartrain will go through its initial cycle. Test out the turntable and tray functions.

I did some other work to try and refurbish this unit. I don't think it mattered, I think the problem was just the loose belt. But just in case, here's everything else I did.

• Deoxit of all ribbon connectors.
• Deoxit on all panel buttons
• 12 hour deoxit soak on the reed switch shown in my previous post.
• Clean the boards with alcohol. Maybe not a good idea, the alcohol seemed to attack the board's coatings.

All that's left is to put the cover back on and play some music. I hope that this thing will be good for another 30 years now.