Aiwa JAX-N1 CD player says no disc

[roli]

Hi!
I am apparently continuing my "vintage" AV gear repair-a-thon. This time on the line is an Aiwa JAX-N1 mini hifi system. Or to be more specific - the CD changer. The whole unit was used many years ago in the kitchen and as far as I know when it was last used it worked fine. Then it was placed in the attic for storage and I decided to finally put it to use a month or so ago. The tape deck had some mechanical issues that were solved with some cleaning and lube and is now working really well. The radio works fine, and the CD section had deteriorated belts for the CD changer carousel and drawer. I replaced those, but sadly that only opened up new issues with the player.

Namely... when I put a few discs in there, it would spin them slightly (quite slowly actually), pause and then try again once or twice. You would hear it clicking a bit and during that and then it would just move on to the next disc. And playing that would also fail. Until it reaches the third disc and then just says "no disc". I tried the CD test mode and I can move the pickup manually in that mode. It moves fine. So the movement seems to be ok.

My first thought it was that the laser unit was dead, so I bought a new laser assembly from aliexpress... there is absolutely no difference with the new unit (and yes, I did desolder the solder blob on the laser assembly).

I have a feeling that there is nothing wrong with the laser module and that the problem lies somewhere else. From what I've searched on the internet the trimmer (there is only one) on the laser assembly should be left alone since this should regulate the laser module current automatically. I am not sure if the disc should spin up fully before the laser tries to read it... if yes then something to do with the spindle speed regulation or something?

Service manual is available here: https://elektrotanya.com/aiwa_cx-jn1.pdf/download.html
Sadly it is quite sparse when it comes to actually finding anything useful in there.

[cantata.tech]

First thing to suspect would probably be the thin ribbon cable connector not making contact somewhere.

[shakalnokturn]

For speed I can't really say, I think most players spin slow until they've actually locked on the disc index, speed difference isn't huge.

A fault I've run into many times is a dirty commuter on the spindle motor or 1 shorted winding out of the 3 then the motor is unable to maintain the right speed to read index.

The clicking sound could be the lens poping up and down while trying to focus on the disk.

If you have an oscilloscope start by looking at the "eye pattern" while the disk spins.

Are there SMD electrolytics anywhere on the CD section?

[roli]

The ribbon cable connecting everything looks fine. It's not a particularly fine pitch affair and there is lots of space in there, so it's not crammed in. I did also unplug and re-plug all of the cables on the CD module. So I don't think it's the cable.

The clicking I think is the protective cover moving, and that seems fine.
No SMD electrolytics to be found on the board. There are a few through hole ones, but they aren't bulging and there don't seem to be any signs of leakage anywhere.

A fault I've run into many times is a dirty commuter on the spindle motor or 1 shorted winding out of the 3 then the motor is unable to maintain the right speed to read index.

Is there anyway to check that?

I was hoping to avoid having to check the eye pattern, because Sony conveniently mounted the test points for measuring this under a soldered on metal can.

I am attaching a few images of the thing, just to give everyone an idea on how it looks.

[shakalnokturn]

The lens dust cover should only move twice at most, once to close when coming to centre position once when leaving centre. You have checked it uncovers when it should?

My method for testing the small DC brushed motors is the Hameg scope's comment tester zoomed, slowly turning the motor by hand.

I'd check the electrolytics all the same, a capacitor can have low capacitance or high ESR without spewing or bulging.

If you remove the he shielding, you gain access to the eye pattern test point (that maybe also available on the FFC connector? I haven't checked the manual.) and you get to check the state of things under there.

Another of my routine checks is the position switches contact resistance, usually not fantastic.

The usual sequence is: Load disc, bring laser to inner position, back off slightly, spin disc while trying to focus.

[David_AVD]

Was the replacement laser a KSS213F like the original (not a KSS213C, etc) ?

I've stopped buying lasers from AliExpress as they all seem to be faulty, used, etc these days.

[roli]

Yes, the replacement was like the original. It looks exactly the same (well the dust cover is blue instead of black, but I don't think that matters) - markings and stickers and everything else looks the same. And the model number is the same as well.

[roli]

Well I finally had time to desolder the stupid can and get to the test points (which are tiny and not even labeled  ).

And something else happened. In CD test mode it actually started playing discs a few times. Not always, but sometimes. You can see the eye patterns in the images. One is from the first time it started playing it, the second one (with higher Vpp) is from subsequent times.

I think the reason why it sometimes works in the CD test mode is because it doesn't give up after a few tries. First of all you can see the actual CD reaching the full speed and then the pattern starts forming. Usually it starts working if I manually advance it a bit forward and tell it to play like track 5 or something. It will then play all of the tracks just fine. But as soon as I go into normal playback mode... it just gives up immediately.

Here is a link to a video of what it does in regular mode: https://cdn.discordapp.com/attachments/893602470675251210/1089588628818235492/IMG_6562.mov