Stereo Repair[IT-RR501] Mode Selector stuck/unresponsive upon power up

[tremulant]

Hello Everyone, a quick summary of my electronics experience. I'm a novice. I've repaired a few things (amplifiers, dehumidifiers, fans, etc)  by replacing obviously visually faulty components.
I've read about 2/3 of Thomas Floyd's text book on Basic Electronics...so I'm decently familiar with the functions, theory, and math...but not well practiced by any means.

I recently acquired a free stereo and am trying to repair it. When I power it up, the LED display will go directly to CD mode and give the prompt "busy". However it remains indefinitely unresponsive.
No CD is in the tray, or cassette or vinyl. All buttons are unresponsive, I cannot change to any other mode including radio. However, I can turn the volume knob and change the volume value...so I know the LED display screen is responsive.

I could not find information within the manual to perform a factory reset, and have not been successful in guessing, such as holding in the power button.

I've began disassembling. I've disconnected the CD players power and information cables. With no change to the condition.

So at this point I'm open to recommendations before proceeding. There are no visible burnt out components as of yet. I'm inclined to think that perhaps the problem lies within the panel of mode selection buttons (tape, record, cd, am/fm, etc)...as I cannot even change to radio mode.

Strangely enough, I found a couple of quarters(coins) within the stereo. One in an harmless area, another balanced randomly on the circuit board. No evidence of shorting and no change upon removing it
(well, 50 cents) . Don't know how they got there, perhaps a kid jammed them in somehow.

If any additional information would be helpful let me know. I will likely continue disassembling and take a look at the selector switches for anything obvious.

Thank you

[tremulant]

Well, in order to even visually inspect the circuitry I had to essentially take apart the entire thing. No obvious visual defects on the selector switch.
Can't say I have any strong intuitions as where to go from here, so I'm looking for some general advice.

1) Is troubleshooting complex circuitry with micro components with no schematics a fool's errand, or is it just advanced and pain-staking?
Is this a waste of time trying to fix?

2) Are manufacturers required to provided electrical schematics to consumers (with or without proof of purchase), or is it often industry secret.

[Bud]

Maybe on power up the device is trying to move the CD lens to home position but not getting a response from the CD drive. Check the CD lens mechanism is not stuck.

These days manufacturers do not provide schematics. Consumer devices are disposable crap mostly.

[tremulant]

Perhaps, worth a look at least. Weird trying to change mode to radio, tape, etc doesn't cancel the attempt to 'move the lens to home position' though. Also, I disconnected the CD power/info cables and it was still trying to read a CD ,"busy". Maybe if the system has a memory, it seems stuck trying to read a CD. Anyway, it's a bit beyond me.

Yeah, I'm impressed with the brilliant  electrical engineering of devices and want to learn how it all works,...but disappointed at how companies often are no help at all when you want repair anything.
It's incredibly wasteful.

Thanks for your reply

[Bud]

My Sony radio/cassette/CD always powers up in CD mode and i can hear the CD motor working for a sec or two at power on. This is how the firnware was written. Do not assume yours was written by an expert. Noone would expect CD being disconnected or its motors jammed, there may likely be no code in the firmware handling that unless it is a high end product.

[tremulant]

I disassembled the CD drive. I don't know how things should be under ideal conditions, but the motor/mechanism next to the lens doesn't spin freely at all and there's a rattling noise when it is spun manually.
If anyone here has enough experience with CD drives to tell if that's normal or not that would be helpful. I probably wouldn't try and replace the motor...but might consider replacing the drive all together. Although that might also be more time/money than it's worth.
Thanks for any input