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Troubleshooting CD Players

dr*audio said:
Why wouldn't you just use the outboard DAC?
Also, I don't remember your original problem but if there is no sound at all, there may be muting transistors that are blown.
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This is totally what will happen.
I guess i was thinking I'd be ambitious and attempt something I'm not knowledgeable in.
Original problem was just faint hum/noise via the analog output.
Seems to be working fine with the outboard DAC so I'll continue using that.
 
I find that a skipping CD player may need the rail the laser rides on needs a little light oil applied. Solved the issue with my Meridian.
 
93SCMax said:
You can try to clean the button switch with DeOxit. Work it 50 times or so. If that doesn't work, time to replace it.

The switch is very common across the unit and other units. I had to replace one for my Tray Open/Close button. Just a little soldering. The hardest part was disassembling the faceplate from the unit.
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Thanks for the suggestions. I tried them both (Deoxit and replacement), unfortunately neither helped.

Many of the buttons on the same circuit board are acting similarly, eg track 4 button will sometimes go to track 5, etc. It's intermittent though.
 
If you are having intermittent failures, maybe look for cold solder joints on the board, or even put down some new solder on all of the button connections. The only other option is finding a replacement board. Any troubleshooting after this is above my pay grade.

With all of your effort, it would be a shame to not get the unit running back to normal.

Good luck.
 
classyharlan said:
Thanks for the suggestions. I tried them both (Deoxit and replacement), unfortunately neither helped.

Many of the buttons on the same circuit board are acting similarly, eg track 4 button will sometimes go to track 5, etc. It's intermittent though.
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Without actually seeing them;
Either most of the button contacts may be contaminated, or an interconnect contact point may be contaminated or intermittent. If there is an interconnecting cable to the button switches, unplug and plug it at the affected ends several times. If no joy, find a button panel replacement if deep cleaning & flushing the button switches and working them wet with a non-residue cleaner doesn't work.
Remember that if alcohol is used to clean them, it is conductive and must be totally blown out and dried before trying them.
 
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classyharlan said:
Thanks for the suggestions. I tried them both (Deoxit and replacement), unfortunately neither helped.

Many of the buttons on the same circuit board are acting similarly, eg track 4 button will sometimes go to track 5, etc. It's intermittent though.
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Check the Vcc for the microprocessor. Best to check it with a scope. If it is low or has ripple on it, it will cause this kind of problem.
 
dr*audio said:
Check the Vcc for the microprocessor. Best to check it with a scope. If it is low or has ripple on it, it will cause this kind of problem.
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Is the wave supposed to be a simple sine wave going 10V top to bottom, anything less than that meaning it's low? Also, does ripple mean visual irregularity?

If it's low or has a ripple, what can be done next?
 
dr*audio said:
This is really strange behavior. I would first check the rf signal with a scope. If that is ok, I would suspect the IC that drives the sled motor.
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This is from a question in February, I asked about a laser that was intermittently jumping past the home position on startup. The RF is about 1.2 albeit jittery. How is the sled motor IC checked?
 
classyharlan said:
This is from a question in February, I asked about a laser that was intermittently jumping past the home position on startup. The RF is about 1.2 albeit jittery. How is the sled motor IC checked?
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Look at the sled motor output with a scope during play. It should be a dc voltage that steadily increases until it gets to the threshold where the motor moves the sled. If it's a geared motor it usually moves at under 1V. If it sometimes goes above 1V and the sled moves too far and jump back its either a bad sled motor or the rails need to be cleaned and lubed.
 
dr*audio said:
Look at the sled motor output with a scope during play. It should be a dc voltage that steadily increases until it gets to the threshold where the motor moves the sled.
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The sled failure happens in less than a second after hitting play or after the tray has closed and it starts trying to recognize the disc so there is no time to see any voltage increase. Even when it doesn't fail and starts playing though, there isn't a visible steady increase, the wave just appears once playback starts.
 
classyharlan said:
The sled failure happens in less than a second after hitting play or after the tray has closed and it starts trying to recognize the disc so there is no time to see any voltage increase. Even when it doesn't fail and starts playing though, there isn't a visible steady increase, the wave just appears once playback starts.
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You have to set the scope on DC coupled or you won't see the voltage.
 
dr*audio said:
its either a bad sled motor or the rails need to be cleaned and lubed.
Click to expand...

After cleaning and lubing the rails and deoxiting the home switch the deck is now consistently reading discs and playing them from track 1. It still fails intermittently during playback and when skipping tracks so I'll try repeating the cleaning and lubing until the problem goes away. I apologize for asking about this problem when the solution was in the top post of this thread, thanks for your patience and continued replies.
 
A while back I posted about my CDP70. I went ahead and got another one. Upon receiving this new one, I realized something: both my old one (now dead) and my new one skip at certain times. I'm convinced that these old CD players just have trouble reading discs that have even minor surface marks on them. Both skip only at certain times, and I mean ONLY at a specific time, probably where a mark is on the disc, so it isn't just random skipping.

When I put these CDs into a newer player, it reads it perfectly. Maybe laser technology got a bit better than in these old players.

Now I'm not sure of this, but a trend I'm noticing is that the skipping happens later on in the CDs. I'm thinking of 2-3 CDs that exhibit the skipping, and all of them happen at the end of the albums. I don't know if that's a coincidence or what. It probably is though, because there are CDs that play all the way through without issue, and if it really was an issue with the rails needing to be lubed for example, it would probably do it on every CD that I had.
 
I think there are threads concerning cleaning CD's.

I've used aluminum car wheel polish to clean the underside of the CD. Work from the center outwards and make sure you get all the dried polish off. CD's that skipped on a certain track, now play fine.

Disclaimer: If the CD is really scratched, nothing is going to fix it.
 
thared33 said:
A while back I posted about my CDP70. I went ahead and got another one. Upon receiving this new one, I realized something: both my old one (now dead) and my new one skip at certain times. I'm convinced that these old CD players just have trouble reading discs that have even minor surface marks on them. Both skip only at certain times, and I mean ONLY at a specific time, probably where a mark is on the disc, so it isn't just random skipping.

When I put these CDs into a newer player, it reads it perfectly. Maybe laser technology got a bit better than in these old players.

Now I'm not sure of this, but a trend I'm noticing is that the skipping happens later on in the CDs. I'm thinking of 2-3 CDs that exhibit the skipping, and all of them happen at the end of the albums. I don't know if that's a coincidence or what. It probably is though, because there are CDs that play all the way through without issue, and if it really was an issue with the rails needing to be lubed for example, it would probably do it on every CD that I had.
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The CDP-101 and CDP-70 have defective power opamps that drive the sled motor. They become noisy and cause skipping. They also have problems with grease hardening.
 
Any suggestions on what to try with this behavior on a Meridian G91A using a DSL-720A drive? Initially it won't read most discs and will show 'loading' on the screen and then 'no disc'. It usually (say 9/10) accepts a copy of Norah Jones' 'Come Away with Me' and after playing all or at least some of the later tracks of this disc it seems to play any other CD I've tried so far, even doing a good job with damaged discs. I've tried letting it warm up for 30 minutes from a cold start and no change. The machine has a new PSU, a clean lens and the sled rails look ok from a quick look but maybe the grease has become too thick.

I haven't read all of this thread (yet, great resource) but have read much and there are many things to try but I'd prefer not to risk making things worse. Guessing I should be trying to lube the spindle bearing and clean and lube sled rails and sled drive mech?
 
A400 said:
Any suggestions on what to try with this behavior on a Meridian G91A using a DSL-720A drive? Initially it won't read most discs and will show 'loading' on the screen and then 'no disc'. It usually (say 9/10) accepts a copy of Norah Jones' 'Come Away with Me' and after playing all or at least some of the later tracks of this disc it seems to play any other CD I've tried so far, even doing a good job with damaged discs.
Guessing I should be trying to lube the spindle bearing and clean and lube sled rails and sled drive mech?
Click to expand...
Yes.
 
Hi dr*audio and others, I am trying to repair a Kenwood DP2080 which I purchased recently as not working properly. This unit dates back to 1990s I think and is a pretty basic model. It uses a Sharp H8151AF optical unit. I don't have the remote control. I do have the service manual. This one has me stumped. Symptoms are as follows. Standby light comes on when plugged in. Unit will not power up when power switch pressed. However, display lights dimly for a few seconds then goes out. The power switch is a soft press type (click on, click off). The optical unit also moves slightly when power switch pressed. I have checked voltages at various points on pcb when in standby mode. There are some issues due to bad caps in the power supply part of the pcb and I have replaced some of these. This has not fixed the problem. Strange thing is, the observed voltages at various points drop when power switch is pressed and stay at that level unless unit is unplugged. Other things to note: optical unit will return to rest position if displaced and unit is plugged into power. If disc tray is manually opened, will close when unit is plugged into power. Spindle motor sometimes spins a little, sometimes not. The power switch seems to be wired to the display unit and not directly to the pcb. Pcb seems to be always always when unit is plugged in. There is a switch on the back of the unit which says auto/manual and I am not sure what this for. Irrespective, it does not have any effect on the issue at hand. Any suggestions greatly appreciated. Glenn
 
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