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Troubleshooting CD Players

Opto5205 said:
Only problem is, to repair a $200 CD player from 30 years ago you need a $5 part that now costs $50. And, it's a really old part.
Or, you can buy a new CD player for $500.
Other than that, yeah, it's a pretty cool technology :)

I still have my lovely Philips CD920 player from 1993, when I was 16 years old. I need a new CD drive unit for it, a CDM12.1/05 because the old one was shot.

Sucker cost me something like 50 bucks, and it will take a month to arrive. This is a 5 or 10-dollar item at most.
Click to expand...

My experience hasn't been thus. Of the 100 or so cd players I've tinkered with in my lifetime, only a few went bad due to a dirty lens, a stretched/broken belt, or something else fixable.

I've only had maybe 2 lasers quit. Even my venerable Yamaha CDX-1100u I let go for not much only needed a new felt grip I was able to replicate with some craft material.

But I do understand what you're saying.
 
onwardjames said:
My experience hasn't been thus. Of the 100 or so cd players I've tinkered with in my lifetime, only a few went bad due to a dirty lens, a stretched/broken belt, or something else fixable.

I've only had maybe 2 lasers quit. Even my venerable Yamaha CDX-1100u I let go for not much only needed a new felt grip I was able to replicate with some craft material.

But I do understand what you're saying.
Click to expand...

That's cool. I have my 30 year old Philips CD920 player and just ordered a new CDM12.1/05 drive for it, because no amount of lens cleaning or fiddling with the laser power will make it read CDs anymore. Sometimes it reads the Table Of Contents (TOC) on the disc, but it will not play any of them at all. The laser still glows red, and the disc spins, suggesting that the focus mechanism still works but it cannot play any discs.

So, I ordered a new CDM12.1/05 drive unit online. The stupid thing was 50 bucks for a 10-dollar item! I hope it shows up in the mail eventually because having anything shipped to Canada is always a pain in the arse.

I really like my cheap old player, it sounds awesome when it works properly. It actually has a proper preamp chip for the analog outputs, instead of just using the DAC chip output directly. I believe it was necessary for the Philips 1-bit Bitstream converter to work, because the output of the DAC chip has a very high output impedance, so a buffer amp is necessary for it to work at all with the input impedance of normal stereo receivers (typically about 50 k-ohms.) The op-amp output makes for less than impressive specs on paper because it adds some noise, but it sounds REALLY good.

But, getting parts for it is an expensive pain in my ass. I'm going to be pretty miffed if the new one doesn't work.
 
No I haven't, the entire circuit board is all original and ~30 years old. Maybe replacing some caps would be a good plan, but the thing is, my player was working fine a couple months ago before it finally quit and it sounded great.

So, replacing capacitors is only something I would want to do if I felt the sound quality was deteriorating, because I don't want to screw anything up! I wish I know what specific capacitors to replace that would directly affect disc tracking and reading, instead of just blindly replacing everything hoping for a vague improvement. This player has a LOT of mileage on it, I got it when I was 16 years old in 1993 and it has been used all day for many, many years.

All of the blue capacitors appear to be ELNA ones, I don't know if they're any good, but the player turns on and sounded really good until it recently quit. I have no idea if those caps would affect laser tracking.

My nearly half-century-old Optonica receiver works well, and the electrolytic capacitors in it are ancient! I could probably replace them too, but feel no need to right now. Even the two power supply rail caps (50V, 6800uF) seem to be working fine even when I crank it up loud.
 
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Capacitors don't just affect sound; they affect basic function, too, especially in power supply filtering. That is the case with many Philips optical drives, which is what I was trying to hint at; your optical drive problems may be down to a bad capacitor.
 
cpt_paranoia said:
Capacitors don't just affect sound; they affect basic function, too, especially in power supply filtering. That is the case with many Philips optical drives, which is what I was trying to hint at; your optical drive problems may be down to a bad capacitor.
Click to expand...

That's what I was wondering about. That CDM12.1/05 drive has little surface-mount capacitors on it, but there's no way for me to know what the values are supposed to be and I have no way of testing them.

It would be nice if I could just fix it, but for now I have no recourse but to buy a very expensive replacement drive unit. You could be right though, maybe a little capacitor has failed, or possibly one of the tiny surface-mount transistors. I wish I could fix it, because the laser still glows red and it sometimes reads the TOC on the disc, but will not play the actual tracks.

It sounded awesome and I'd love to fix it. CD players are far too expensive these days for a technology that's very cheap.
 
cpt_paranoia said:
Oh, if they're SMDs, they're not the notorious axials...
Click to expand...

Nope, no axials. All the bigger capacitors are Elna ones with both leads on one end.

The CD drive unit has a flexible flat cable that has little SMD bits on it. A few transistors, resistors and caps, and a tiny trimmer pot for adjusting the laser current.
 
Nakamichi CD-4 here that I'd like to see if I can get working.

Not to be confused with the Nak "CD Player 4".

The "CD-4" was mentioned a couple times earlier in this thread and my symptoms are similar. I didn't see any resolution to those cases after reading through the whole thread.

Nice lady gave me this deck for free, not working. She said she took it in to a shop and was told it was "Not repairable". I suspect that they just really meant it's not worth the expense. So I thought I would just treat it as a learning exercise. It would be nice if I could revive it, but I am willing to cut bait too if it becomes a fools errand. I've tried to find the SM but no luck so far.

Looking inside it has all Nichicon caps, including a tone of the Green Muse's. Only a single AD1865 DAC chip. But at least it does have digital out capability.

So anyway, here goes. I am going to list out the symptoms and observations so far and see what y'all think. Especially you @dr*audio !
  • CD physically loads just fine. Drawer moves smoothly and transport moves into position both with, and without a disc.
  • Laser transport moves into home position (doesn't move back like a typical transport, but others with CD-4's noticed the same thing).
  • I did remove the PCB for access and cleaned the home/stop switch. No change.
  • Using my cell phone I can see the red laser light when I power the unit on. It goes out as expected when it doesn't load TOC/ recognize disc. (see pic attached)
  • When initialized laser lens does pop up and down once trying to focus. (it only does it once, not sure if this is normal, other transports I've seen it bounce a couple times trying to focus)
  • Pin 1 of C105 = ±1.9v an then fades after initialization.
  • With no disc inserted, initialization results in spindle motor rotates 7/8 to 1.5 rotations (as observed with a witness mark on top clamp)
    Note: there is a slight ssst, ssst, sound that appears to be top clamp rubbing due to lack of thickness of CD.
  • With disc inserted, initialization results in spindle motor rotates only 1/4 turn and it's pretty slow at that.
    Note: above mentioned ssst sound is absent. If I manually spin disc there is no indication of rubbing.
  • With transport assembly removed I applied 3v to spindle motor (Matsushita MDN-4RA3FTAS 3v motor) by connecting 2x AA batteries in series. Spindle motor spins freely and quietly. (but I did not measure current draw)
  • With transport assembly fully hooked up and initialized I measured voltage across spindle motor + and - terminals and it would spike to between 0.9 to 1.3v and immediately drop to zero. (am I just measuring voltage drop across motor here?)
    If I measured between positive terminal of motor to ground I get 0v.
So that's as far as I've gotten. I'm leaning towards thinking spindle motor is suspect? But I don't quite understand the logic sequences of startup, so it wouldn't surprise me if the laser failing were causing the spindle to not actually spin up.

Edit: I did try oiling the spindle motor and running for a minute or so on battery power to work the oil in. No difference to behavior.

I do have an old Tektronix scope and so far have mastered turning it on. I have more tenacity than actual electronics knowledge. But my mechanical abilities are pretty good. My old aeronautical engineer uncle used to tell me I was one of the most natural "Barnyard Engineers" he's met...LOL.

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I think the spindle motor is ok and you have a bad laser. It appears to be a KSS-210A and you can buy good ones from Liberty Electronics on E-bay. Don't buy it from any other supplier, they may be junk.
I would suggest you look at tutorials of how to use an oscilloscope, on YouTube. Then connect your scope to the RF testpoint, if it's labelled, load a disc and see if you are getting at least a blip. I suspect not.
When you replace the laser, wear a grounded antistatic wrist strap. There is a little blob of solder on the circuit board of the new laser that protects against ESD and it must be removed.

dogwan said:
Nakamichi CD-4 here that I'd like to see if I can get working.

Not to be confused with the Nak "CD Player 4".

The "CD-4" was mentioned a couple times earlier in this thread and my symptoms are similar. I didn't see any resolution to those cases after reading through the whole thread.

Nice lady gave me this deck for free, not working. She said she took it in to a shop and was told it was "Not repairable". I suspect that they just really meant it's not worth the expense. So I thought I would just treat it as a learning exercise. It would be nice if I could revive it, but I am willing to cut bait too if it becomes a fools errand. I've tried to find the SM but no luck so far.

Looking inside it has all Nichicon caps, including a tone of the Green Muse's. Only a single AD1865 DAC chip. But at least it does have digital out capability.

So anyway, here goes. I am going to list out the symptoms and observations so far and see what y'all think. Especially you @dr*audio !
  • CD physically loads just fine. Drawer moves smoothly and transport moves into position both with, and without a disc.
  • Laser transport moves into home position (doesn't move back like a typical transport, but others with CD-4's noticed the same thing).
  • I did remove the PCB for access and cleaned the home/stop switch. No change.
  • Using my cell phone I can see the red laser light when I power the unit on. It goes out as expected when it doesn't load TOC/ recognize disc. (see pic attached)
  • When initialized laser lens does pop up and down once trying to focus. (it only does it once, not sure if this is normal, other transports I've seen it bounce a couple times trying to focus)
  • Pin 1 of C105 = ±1.9v an then fades after initialization.
  • With no disc inserted, initialization results in spindle motor rotates 7/8 to 1.5 rotations (as observed with a witness mark on top clamp)
    Note: there is a slight ssst, ssst, sound that appears to be top clamp rubbing due to lack of thickness of CD.
  • With disc inserted, initialization results in spindle motor rotates only 1/4 turn and it's pretty slow at that.
    Note: above mentioned ssst sound is absent. If I manually spin disc there is no indication of rubbing.
  • With transport assembly removed I applied 3v to spindle motor (Matsushita MDN-4RA3FTAS 3v motor) by connecting 2x AA batteries in series. Spindle motor spins freely and quietly. (but I did not measure current draw)
  • With transport assembly fully hooked up and initialized I measured voltage across spindle motor + and - terminals and it would spike to between 0.9 to 1.3v and immediately drop to zero. (am I just measuring voltage drop across motor here?)
    If I measured between positive terminal of motor to ground I get 0v.
So that's as far as I've gotten. I'm leaning towards thinking spindle motor is suspect? But I don't quite understand the logic sequences of startup, so it wouldn't surprise me if the laser failing were causing the spindle to not actually spin up.

Edit: I did try oiling the spindle motor and running for a minute or so on battery power to work the oil in. No difference to behavior.

I do have an old Tektronix scope and so far have mastered turning it on. I have more tenacity than actual electronics knowledge. But my mechanical abilities are pretty good. My old aeronautical engineer uncle used to tell me I was one of the most natural "Barnyard Engineers" he's met...LOL.

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Click to expand...
 
Hi, dr*Audio and others! I want to share my problem with my lovely Denon DCD-1520. Very nice player! A strange issue starts a couple of days ago. The machine stops to read TOC. So I opened it and what I obverse is that the CD is spinning backward! It's trying to start normally and then go to opposite way. Interesting the player is NOT doing this all the time! It plays Some CDs just well. I had a Dual turntable that spins the turntable backward and the problem was the motor disc capacitor. I replaced it and the machine starts to spin the vinyl records normally. At first look the problem is the same but why does it spin some CDs normally? I just downloaded the Service manual but didn't read it yet.
Any help, idea, or advice is appreciated!
 
Spinning backwards means it is spinning too fast, so it's braking. Most likely the laser power is low and it can't read the data correctly. The laser is NLA.
 
Thanks, dr*Audio!! Few questions(I appreciate your time!!) What is the other name of Laser Power? Focus gain, or Tracking gain? Or Focus offset? These are adjustments in the Service book. These adjustments look like a very complicated job! I'm not pretty sure I would be able to do it but I would try it...If I get some help of course... I have a dual track oscilloscope, Frequency counter, Digital VM, AC millivolt meter with dB. I don't have an oscillator. When I make a calibration on some cassette deck, usually I use my laptop and the Audio Measurement System program as a tone generators. In this program (which I use as Generator) the amplitude is in dB.
The service manual says: Oscillator 690hz 1 Vp-p( is it peak to peak?). Is there any way to convert 1Vp-p(however what does it mean?) to db so I can use my laptop as an oscillator??
Thanks for every answer!
I know I ask too much...
 
ivo said:
Is there any way to convert 1Vp-p(however what does it mean?) to db so I can use my laptop as an oscillator??
Click to expand...

Your AMS program is likely to be reporting dbFS (i.e. relative to full scale of whatever digital sample range it is using for generation); the absolute output level (voltage) will depend on the gain of your laptop's audio output stage. The easiest way to get a 1Vpp (yes, peak-to-peak) is to just generate an output signal at 690Hz, feed it into your scope, and adjust the output level in AMS until you get 1Vpp.
 
ivo said:
Thanks, dr*Audio!! Few questions(I appreciate your time!!) What is the other name of Laser Power? Focus gain, or Tracking gain? Or Focus offset? These are adjustments in the Service book. These adjustments look like a very complicated job! I'm not pretty sure I would be able to do it but I would try it...If I get some help of course... I have a dual track oscilloscope, Frequency counter, Digital VM, AC millivolt meter with dB. I don't have an oscillator. When I make a calibration on some cassette deck, usually I use my laptop and the Audio Measurement System program as a tone generators. In this program (which I use as Generator) the amplitude is in dB.
The service manual says: Oscillator 690hz 1 Vp-p( is it peak to peak?). Is there any way to convert 1Vp-p(however what does it mean?) to db so I can use my laptop as an oscillator??
Thanks for every answer!
I know I ask too much...
Click to expand...
The oscillator is only used for focus and tracking gain and isn't necessary. Usually these don't have to be adjusted anyway.
Laser power is laser power. There is a trimpot on the laser on the small PCB, and you can adjust it by looking at the RF waveform with your scope and adjusting for 1.5V p-p on the scope, playing a commercially produced CD. Focus Offset is likewise adjusted using the RF waveform and adjusted for max amplitude and clearest waveform.
Tracking offset is adjusted using the procedure in the manual.
Your laser power is low. If you can adjust it up to spec, monitor it for at least 1/2 hour, because in a failing laser it will just slowly drop off and then you won't be able to bring it up anymore. If it doesn't drop off, you might get a few more months out of it.
 
Thanks, dr*Audio! Thanks, cpt_paranoia! A lot of good information! Once again I convince myself that AudioKarma is the best place for electronic's hobbyists! I gues it is nice place for enginiers and pro tech too.
I'll try to adjust the laser power to 1.5v, but obviously, this player is done. Unfortunately KSS-151A is really expensive $420 and up. This is make any replacment out of sence.
 
The KSS-151A was widely used; check the list at Dutch Classics. If you're that keen on the 1520, maybe you can find a cheap, working 2nd hand unit to salvage a laser assy from. But you may run into the laser life problem again...
 
Ok. I adjusted the small trim pot on the laser unit. It needs a less-than-hair move CCW. Now the player read ALL CDs which was unreadable before. No backward spinning anymore. No fault with any CD. I don't know how long the unit will stay in this condition, but so far it works great.
Thanks for all your help and advice!
 
Have this NAD 5000 CD player, it's not reading /playing cd's before its warned up or Been turned on for a while.

Cleaned lens. Oiled the spindel motor.
Any suggestions?

Tnx.
 

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