Sorry for being late... worked on the thing 'til almost midnight last night, was exhausted, too late and tired to report back.
I did wonder why the tendency towards multi disc players
There seems to be a pattern indeed, judging but the success of my two 5 disc changers. Also, the guy over at 12voltvids repair channel on YT , commented about this very thing. He too noticed an appetite for 5 disc (carousel) changers (not sure about 6 disc cassette changers though), which he can only explain this way : "You get that hot chick at home, turn the machine on at the start of the date and just forget about it. You dont want the music to stop suddenly while in the middle of.... ahem. ". I don't know.
Personally, I do enjoy my old Philips CDC486 6 disc cassette changer. Whenever I work on, the lav it always takes hours on end, I just want some background music. I just hit PLAY when I start working, and power the thing off at 2AM when I am too tired to work on the bench and decide to go to sleep.
I really don't fancy having to stop what I am doing every hour or so, to swap CD's ! I just hit PLAY and forget about it. Using a single disc player and getting it it to repeat the disc endlessly, is not a satisfactory option I am afraid
[..] you wouldn't find any self-respecting vinyl addict using an autochanger turnable (remember those?)
Gyro, big mistake here !
You are assuming that people are trained and passionate audiophiles ?!
Obvisouly nothing could be further from the truth, otherwise CD player manufacturers would never have been able to sell hundreds of millions of their CD players for a couple decades !
Also, audiophiles tend to seek perfection (something they can't even define in accurate technical terms) for the sake of it. Most people do things to achieve a goal, not for the sake of doing something as such.
The goal of listening to music is to get emotions. Will I have zero emotions if I listen to my favorite songs on a TDA1543 and be flooded with tears wit ha TDA1541 ?! No of course. The later will be more a little more enjoyable, but I would still enjoy my music on the former, as I am doing right now as I am writing this. Because the emotion in the music is not conveyed by its technical perfection... thank god there is more to music than numbers and maths. There is irrationality.
Would you not love you other half if she got a cold and her voice sounded different than when you first met her ? I hope not.. because there is more to her than just he voice. You won't dump her or divorce because her voice sounds a little different.
So, it's functionality first. As long as the changer put out sound, it's good enough for people.
So maybe I could specialize in 5 disc players, knowing they sell better than the single disc ones.
Single disc one I could specialize in the old Philips like my CD824, ie old enough to interest Philips collectors/speculators, therefore command decent/worthwhile prices, but too crap technically to be of any value to me, so I am not tempted to keep them for myself and therefore lose money rather than make any...
Yeah, maybe with these two kinds of players, I could make buck here and there from time to time, can't hurt, I need every penny to build my house.
You seem to have covered everything that I would have thought of ie, check the sensors - I suppose you checked the signals right back to the micro pins (just in case it has a bunch of dry joints).
Almost. Accessibility is a pain on this unit, so I did the best I could in my first / quick attempt : I probed on the main board, on the top side of the connector.
But since the signals were OK there, I dug farther and pulled the (single sided) main board so I could check the underside (where the CPU is soldered). NO dry joints, traces in perfect condition. The sensor for the turn table is digital and goes straight to the CPU pin. However the signal for CD detection is analog and does not go straight to the CPU. In between there is a PNP transistor and a couple resistors, that invert the polarity of the signal. I checked the output of the inverter, works just fine.
So, the CPU does get good table and disc sensors signals. I don't think there is any synchro to be done for the carousel. Manual does not talk about it, and underneath the carousel you can see lots of slots/slits for the optical sensor, carefully laid out to encode the position of the carousel. The whole point I think is precisely to let the CPU figure out by itself the position of the carousel.
It's irritating when it's 'deliberately' doing the wrong thing - from your description of the backwards / forwards it sounds as if it is definitely searching for a sensor input that it is not getting (sensor out of sync, dining table position out by 180 degrees?)
It indeed looks like such "complex" and repeatable behaviour can only emanate from the CPU, something clever... however I am slowly considering that it may not be the case....somehow ?I mean, I am so clueless and baffled, that I am now considering any possibility, as long as it gets the thing fixed ! LOL
Here are the things that would make it strange if it were the CPU at fault : the problem is present at ALL times... even if :
1) I put the unit in table maintenance mode.
2) I open the tray.
3) If disconnect the front panel, and the CDM / BD board. leaving nothing but the main board connected to the turntable motors and sensors. In that case, I would expect the CPU at power up to be somewhat disturbed by the lack of front panel and CDM / player, at least sufficiently disturbed to decide there must be something better to do right now, than play again with that bloody turntable...
A corrupted CPU firmware ? I guess that's very low on the list...
Things that may point to a H/W issue :
1) When the carousel moves from one slot to the next.. and back again, between two slots it always, consistently kinda stops, but not really : it slows down to a crawl, makes a sorry "grinding" noise while moving extremely slowly, like a millimeter a second... then all of a sudden starts moving fast, smooth and quiet again... and the cycle repeats. So, this means the CPU is would be programmed to be able to generate analog voltages to command the motor driver IC, so that it can vary the speed. Sound unlikely....
2) I sometimes, sometimes, notice that the other motor, the "loading" motor as they call it, the one that opens the tray... well sometimes it TOO does some completely weird things. "analog" kind of things.... Both motors are driven by the same chip.... chip that drives nothing but these two motors...
So since I am desperate and the sensor/CPU basic checks lead to nowhere, I am now starting to get at the bottom of things :
1) I had to replace the loading motor belt, and carousel belt, since the original belts were too tired / loose to work at all.
I dismantled 4 CD players, hoping to find belts in them that would do the job. All I could find where belts that were either a tad too long hence useless, or way too short, like half the size (not kidding). Yet, even at half the size, they would stretch and not break. So, given no alternative for now, I used these super tight belts.
So, to rule out a problem with these belts, or a tired motor say, I tested the table outside the CD player. I powered the carousel motor and loading gear motor directly with my lab power supply. Result ? My super tight belts work just fine. Carousel turns effortlessly, smoothy and quiet. The loading motor works fine too. Healthy, smooth.... works just fine.
So now I can rule out any belt motor or gear problem. The mechanical stuff does work fine !
So if it does funny things, it can only be the electronic stuff commanding it.
2) Now next on the list : I will try to power the motor driver IC board (it's not part of the main board), independently, to see if it does funny business or not.
I mean, it uses the same kind of driver IC that failed in that other Sony player I am currently fixing as well (waiting for china to deliver that chip...) So maybe the chips from this manufacturer are just crap...
The cycling nature of the carousel movements might be explained by a capacitive effect of some sort, potentially ? Potnetially.
3) if the driver board does not misbehave on its own, then next thing to do is plug the driver board back to the mainboard, and scope the input signals of the driver IC, to see if they correlate with the misbehaviour. IF they do, the CPU is sending them. If they don't... the driver board/chip is doing it on its own.
So, planning on do that this afternoon. Stay tuned
Hopefully you mean 'Japlish', unless Sony were so cheap that they subbed out their design and manual writing too!
P.S. From my past career, I am experienced in understanding and writing in Konglish. Of course, without the 'lish element I am totally screwed! This probably explains my difficulty with Californian, which bares only a passing resemblance to English.
Ah well, you know more than I do so... maybe Japlish it is, maybe !
Tell me your thoughts : here are below the 3 pages of the manual that pertain to the maintenance mode...