Spectrum77
Super Member
I found this while searching for an owner's manual and general info for the Denon DCD1510 (1500) I recently won on an auction site. Looked good to share with the novices like me.
Reference: http://www.fixya.com/support/t166712-pd_65_skipping (Greg Danner).
Here's how to diagnose a skipping CD player yourself:
First make sure your discs are clean! Or try a fresh new disc. Or if
you have more than one CD player, pick out a disc that is known to
always play perfectly on the good player.
Diagnosing a dusty or dirty laser optical pickup lens or a servo system
that is out of alignment:
The CD player will be FINE on some discs, but flaky on other ones. But
the problem on any given disc WILL NOT get either BETTER or WORSE after
the player has been running for 20 minutes to an hour (see below for
what it means if the player gets worse after warmup).
This is because not all discs have the same light reflectance/raw
signal output to the pickup. If the outside of the player or the tray
you put the disc in actually look dusty, then there may be enough dust
on the lens to reduce the light output too much (does your cat like to
sleep on top of the CD player?). Remember, light has to go through the
lens TWICE to actually play a CD -- the laser diode creates a beam of
light which is sent up through the lens, focussed to a tiny spot on the
CD data layer. The light reflected back into the lens is then picked
up and turned into a electrical signal by photodiodes. So ANY dust or
dirt on the lens itself cuts down the signal coming out of the optical
pickup to the electronics in the CD player TWICE.
Unfortunately, most of the discount store "CD lens cleaner" discs don't
really work too well, so it is probably best to have your player
professionally cleaned if you think dust is the problem.
Sometimes the internal electronic servo adjustments will also drift and
need to be recalibrated, even if the player isn't dusty or dirty
inside. This is done by connecting the RAW OPTICAL SIGNAL, also known
as the "RF" or "eye" signal to an oscilloscope. Then the "eye pattern"
is viewed on the oscilloscope and the servo adjustments are tweaked to
maximize the amplitude and purity of the "eye pattern." This takes a
bit of experience and training on the part of the technician, and as
not all CD players have the same internal arrangement of adustments, a
service manual is often needed to do this.
In-shop cleaning and checkout by a trained technician should cost
between $20-50 for most localities and CD players. Add another $20-30
to this total if the servo needs to be realigned also. If dust on the
lens or servo misaligment truly was the cause of the skipping problem,
doing this should COMPLETELY eliminate the problem.
Checking for a loose spindle motor:
Main symptom: Random skipping, but also the player is MUCH more
vibration sensitive than it used to be when it was new -- light
tapping, or shaking it gently, or walking near the stereo causes it to
skip. Spindle motors usually go bad at an age of from 2 to 5 years,
faster if CD player is used several hours every day. To CONFIRM loose
spindle motor bearings as the cause of skipping, raise the RIGHT side
of the CD player up off the table until the CD player is at maybe a 30
to 45 degree angle while playing a disc. Or just put a dictionary or
other big thick book under the right side of the CD player. If doing
this REDUCES or ELIMINATES the random skipping, then the spindle motor
bearings are getting loose. This problem will gradually get worse over
time. Of course, you might get by for a while by just leaving the
player propped up at one side on top of the dictionary!
Diagnosing a weak laser optical pickup:
Weak pickups can cause a player to start skipping or even totally stop
playing and give a "No Disc" readout part way through a CD. Sometimes
the audio will get distorted right before the player skips or stops.
And if you try to replay a disc right away, it either still skips or
won't even initialize (read out the playing time and number of tracks).
BUT: If you turn off the CD player and wait 20 minutes to an hour, then
it will almost always be JUST FINE for a little while (like 5 to 10
minutes) before it starts acting up again.
This TIME ELEMENT is a classic symptom of a bad laser diode in the
optical pickup. All Cd pickups have an internal feedback system for
controlling the actual light output from the laser diode, as the light
output is strongly dependent on the temperature of the laser diode
(light output from a diode laser drops as the temperature increases-
the first diode laser made back in the 1970s only worked when cooled by
liquid nitrogen!). When the laser diode gets weak, the light control
system pumps EXTRA CURRENT through the laser diode, which heats it up,
reducing the light output even more. Eventually, the light control
system runs out of extra current to supply the diode, and abruptly the
light output drops too low to get a signal back from the disc as the
laser diode heats up. Then the CD player just stops dead in its tracks
until the laser diode cools off (the laser diode is only turned on
WHILE a disc is actually spinning in the CD player).
While a laser optical pickup is one of the more expensive parts to
replace in a CD player, it still might be cost-effective to replace it
if you like the CD player a lot. Replacement optical pickups have
gotten much cheaper lately, and there are about 6 real common ones that
almost all manufacturers use. Unfortunately, Pioneer is one of the few
manufacturers who make most of their own proprietary CD player pickups,
so a new pickup for a Pioneer may cost more (up to $95 or so) than a
pickup for any other brand. A lot of CD players use Sony or Philips
laser optical pickups, and some of these only cost $25 each from parts
distributors like MCM or Dalbani (this price is just for the CD pickup
itself)!
So, what else could cause skipping besides a bad optical pickup or a
bad spindle motor?
Loose/bad/cracked solder joints anywhere on any circuit board in the
unit, intermittent/defective flat flexible cables,, electrolytic
capacitors with high ESR (dried out) anywhere in the player, servo
system not aligned right (requires test equipment: oscilloscope),
rubber spring mounts for the transport section worn or not assembled
right, disc rubbing on a warped tray, intermittent/defective sled drive
motor, bad IC or transistor somewhere in the servo circuit.
Most of these would be hard for the consumer to diagnose, but should be
easy for a well-trained technician to find and fix!
If none of these tips help, I'm one of those people who buy broken CD
players to fix and resell. On my bench right now is a classic Denon
DCD-1500, one of the first true audiophile grade CD players from the
1980s. I just put a new optical pickup in it, and it sounds WONDERFUL!
Reference: http://www.fixya.com/support/t166712-pd_65_skipping (Greg Danner).
Here's how to diagnose a skipping CD player yourself:
First make sure your discs are clean! Or try a fresh new disc. Or if
you have more than one CD player, pick out a disc that is known to
always play perfectly on the good player.
Diagnosing a dusty or dirty laser optical pickup lens or a servo system
that is out of alignment:
The CD player will be FINE on some discs, but flaky on other ones. But
the problem on any given disc WILL NOT get either BETTER or WORSE after
the player has been running for 20 minutes to an hour (see below for
what it means if the player gets worse after warmup).
This is because not all discs have the same light reflectance/raw
signal output to the pickup. If the outside of the player or the tray
you put the disc in actually look dusty, then there may be enough dust
on the lens to reduce the light output too much (does your cat like to
sleep on top of the CD player?). Remember, light has to go through the
lens TWICE to actually play a CD -- the laser diode creates a beam of
light which is sent up through the lens, focussed to a tiny spot on the
CD data layer. The light reflected back into the lens is then picked
up and turned into a electrical signal by photodiodes. So ANY dust or
dirt on the lens itself cuts down the signal coming out of the optical
pickup to the electronics in the CD player TWICE.
Unfortunately, most of the discount store "CD lens cleaner" discs don't
really work too well, so it is probably best to have your player
professionally cleaned if you think dust is the problem.
Sometimes the internal electronic servo adjustments will also drift and
need to be recalibrated, even if the player isn't dusty or dirty
inside. This is done by connecting the RAW OPTICAL SIGNAL, also known
as the "RF" or "eye" signal to an oscilloscope. Then the "eye pattern"
is viewed on the oscilloscope and the servo adjustments are tweaked to
maximize the amplitude and purity of the "eye pattern." This takes a
bit of experience and training on the part of the technician, and as
not all CD players have the same internal arrangement of adustments, a
service manual is often needed to do this.
In-shop cleaning and checkout by a trained technician should cost
between $20-50 for most localities and CD players. Add another $20-30
to this total if the servo needs to be realigned also. If dust on the
lens or servo misaligment truly was the cause of the skipping problem,
doing this should COMPLETELY eliminate the problem.
Checking for a loose spindle motor:
Main symptom: Random skipping, but also the player is MUCH more
vibration sensitive than it used to be when it was new -- light
tapping, or shaking it gently, or walking near the stereo causes it to
skip. Spindle motors usually go bad at an age of from 2 to 5 years,
faster if CD player is used several hours every day. To CONFIRM loose
spindle motor bearings as the cause of skipping, raise the RIGHT side
of the CD player up off the table until the CD player is at maybe a 30
to 45 degree angle while playing a disc. Or just put a dictionary or
other big thick book under the right side of the CD player. If doing
this REDUCES or ELIMINATES the random skipping, then the spindle motor
bearings are getting loose. This problem will gradually get worse over
time. Of course, you might get by for a while by just leaving the
player propped up at one side on top of the dictionary!
Diagnosing a weak laser optical pickup:
Weak pickups can cause a player to start skipping or even totally stop
playing and give a "No Disc" readout part way through a CD. Sometimes
the audio will get distorted right before the player skips or stops.
And if you try to replay a disc right away, it either still skips or
won't even initialize (read out the playing time and number of tracks).
BUT: If you turn off the CD player and wait 20 minutes to an hour, then
it will almost always be JUST FINE for a little while (like 5 to 10
minutes) before it starts acting up again.
This TIME ELEMENT is a classic symptom of a bad laser diode in the
optical pickup. All Cd pickups have an internal feedback system for
controlling the actual light output from the laser diode, as the light
output is strongly dependent on the temperature of the laser diode
(light output from a diode laser drops as the temperature increases-
the first diode laser made back in the 1970s only worked when cooled by
liquid nitrogen!). When the laser diode gets weak, the light control
system pumps EXTRA CURRENT through the laser diode, which heats it up,
reducing the light output even more. Eventually, the light control
system runs out of extra current to supply the diode, and abruptly the
light output drops too low to get a signal back from the disc as the
laser diode heats up. Then the CD player just stops dead in its tracks
until the laser diode cools off (the laser diode is only turned on
WHILE a disc is actually spinning in the CD player).
While a laser optical pickup is one of the more expensive parts to
replace in a CD player, it still might be cost-effective to replace it
if you like the CD player a lot. Replacement optical pickups have
gotten much cheaper lately, and there are about 6 real common ones that
almost all manufacturers use. Unfortunately, Pioneer is one of the few
manufacturers who make most of their own proprietary CD player pickups,
so a new pickup for a Pioneer may cost more (up to $95 or so) than a
pickup for any other brand. A lot of CD players use Sony or Philips
laser optical pickups, and some of these only cost $25 each from parts
distributors like MCM or Dalbani (this price is just for the CD pickup
itself)!
So, what else could cause skipping besides a bad optical pickup or a
bad spindle motor?
Loose/bad/cracked solder joints anywhere on any circuit board in the
unit, intermittent/defective flat flexible cables,, electrolytic
capacitors with high ESR (dried out) anywhere in the player, servo
system not aligned right (requires test equipment: oscilloscope),
rubber spring mounts for the transport section worn or not assembled
right, disc rubbing on a warped tray, intermittent/defective sled drive
motor, bad IC or transistor somewhere in the servo circuit.
Most of these would be hard for the consumer to diagnose, but should be
easy for a well-trained technician to find and fix!
If none of these tips help, I'm one of those people who buy broken CD
players to fix and resell. On my bench right now is a classic Denon
DCD-1500, one of the first true audiophile grade CD players from the
1980s. I just put a new optical pickup in it, and it sounds WONDERFUL!
