A problem with a cd player

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Hello

A friend of mine do have a kenwood DP-460 cd player with a cd playing problem.

My friend was sure that the laser was burned, but I
decide to test his Kenwood cd player, wen I use commercial music cd it
work perfect, but wen I use burned cd-r music, this Kenwood cd player can
not play more than 7 track, after 7 track it do jerky sound with the
music, it look like it can not follow those track.

Any hints of what could be the problems ?

Here is a link to a part of the schematic of the kenwood DP-460 cd player.

http://img101.imageshack.us/img101/4599/kenwooddp460smallfy3.jpg

Thank

Bye

Gaetan


Re: A problem with a cd player
On 1/27/2009 11:23 PM Gaetan Mailloux spake thus:

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You don't need a schematic to figure out that many CD players have
problems with CD-R discs. I've seen this on my own equipment. Depends on
the type of CD-R discs *and* the recorder they were burned on.


--
Made From Pears: Pretty good chance that the product is at least
mostly pears.
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Re: A problem with a cd player
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Home recorded CDs ain't the same as commercial ones and some CD players
simply can't cope with them. And re-recordable seem to be more prone to
these problems than use once types. Think it's to do with the type of
reflective layer.  Strangely, very old ones seem ok - I have an early
Philips dating from the '80s which does. Newish ones should be ok too.
It's the inbetweens that can be a problem.

--
*Learn from your parents' mistakes - use birth control.

    Dave Plowman         snipped-for-privacy@davenoise.co.uk           London SW
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Re: A problem with a cd player

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Likely to be poor laser performance. CD-R discs are nowhere near as
reflective as commercial 'pressed' types, and many players that were not
specifically designed to cope with them, struggle, particularly if the laser
is marginal, or even dirty. Have you, as a first move, tried cleaning the
lens ? (properly with alcohol etc, not a cleaner disc).

As you get further into a disc, its rotational speed falls to maintain CAV.
If the performance of the spindle motor is anything less than perfect, its
speed can be minutely erratic. If the performance of the laser is down as
well, then when you combine these factors, which are typically present in
any player older than a few years, the result tends to be poor tracking
performance / general playability problems on late tracks, and this will be
exacerbated by use of CD-R discs.

Arfa



Re: A problem with a cd player
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I agree - the OP should definitely clean the laser. Other maintenance, such
as cleaning and lubricating other moving parts - rails, gears, motor
spindles, etc, is also indicated. If after cleaning and maintenance issues
are resolved the problem persists, another brand of CD-R's might help, or
the laser may just be deteriorated to that point, especially if in a dusty
and/or smoky environment.

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Perhaps because audio CD's are CLV...

;-)


Mark Z.


Re: A problem with a cd player
"Mark Zacharias" (mark snipped-for-privacy@labolgcbs.net) writes:
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Hello

Cleaning the laser lens and lubricating the mechanicals was the first
thing I have done.

I did try other cd-r brand but the problems still there.

Maby the laser are at the end of his life ?

Thank

Bye

Gaetan

Re: A problem with a cd player
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If you have access to an oscilloscope, the HF "eye" pattern can be observed,
and may be noisy. This would account for the deteriorated performance first
on CD-R's. As previously noted, this is often the result of dust and smoke
contamination. The finest particles get inside the laser, and settle on the
turning mirror as a fine film. This diffuses the reflected laser light
coming back off the disc before it can really be read. It is sometimes
worthwhile to adjust the Focus Offset for maximum amplitude as viewed on the
scope. If it makes a difference of about 20% or more, this may solve your
problem, at least for the short term.


Mark Z.

Mark Z.


Re: A problem with a cd player
"Mark Zacharias" (mark snipped-for-privacy@labolgcbs.net) writes:
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get further into a disc, its rotational speed falls to maintain
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Hello

I have an old Telequipment scope who goes up to 1 mhz, it should do the job.

I've look on the main pcb and there is 4 trimpot; T.BAL , F.BAL , FEOF , TEOF

Wich one are for adjusting the Focus Offset ?

Thank a lot

Gaetan

Re: A problem with a cd player
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FEOF should be the one, but a 1 meg scope won't really get it. You can
adjust for maximum envelope size, which probably is good enough, but you
can't look at the diamond shaped center area of the expanded "eye" pattern
as viewed on a 30mHz or higher scope. Sometimes a x10 probe is required, but
in my experience it is rare for a direct probe to load down this
measurement.

You can "Google CD eye pattern" and see what I'm talking about.

Mark Z.


Re: A problem with a cd player

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All that Mark says, but before you start, CAREFULLY mark the EXACT positions
of the pots before attempting adjustment. If you do adjust more than one of
them (the temptation *will* be there - trust me !!) and you do not have the
proper bandwidth 'scope, and the experience to know exactly what you are
adjusting and why, it is staggeringly easy to get those pots to a point
where nothing will be read at all, often with just a few degrees
mispositioning of a couple of them. Re-finding the correct places to get it
going again, can then be a most frustrating excercise ...

Arfa



Re: A problem with a cd player
"Mark Zacharias" (mark snipped-for-privacy@labolgcbs.net) writes:
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Hello

I will borrow a Sencore SC61 scope to a friend who do not use it, maby I
will buy it anyway since it is doing nothing in his basement.

Btw, what would be T.BAL , F.BAL, TEOF ?


Thank for your help

Bye

Gaetan

Re: A problem with a cd player

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T.B(AL) is tracking balance. Sometimes also known as E-F BAL (named for the
designations of the two photodiodes, "E" and "F" in the pickup, which are
responsible for generating the tracking control signal). It is required in
order to remove unwanted positional offsets of the lens which would
otherwise be caused by imbalances in the tracking servo photodiodes in the
pickup, and the following opamp in the tracking servo processor.

F.B(AL) is focus balance. Does the same for the focus servo circuitry as
TBAL does for the tracking.

TE(OF) is tracking error offset. Allows the electrical zero point of the
tracking servo to be set to match the lens suspension mechanical zero. It is
needed to offset mechanical errors in the construction of the laser, and
electrical servo errors which may creep in as a result of imperfect opamps
etc in the servo amplifier.

FE(OF) would be the same thing for the focus servo, and is needed to correct
for such things as an error in the turntable height, and similar servo
electrical errors.

You may find a pot called PLL on some players. The setting of this is
*extremely* critical to data recovery from the disc, and requires an
accurate frequency counter to set it up. NEVER adjust this pot randomly,
even if you think that you have marked its original position perfectly.

It is rare to find any of these adjustments present, in modern players. The
servo processor ICs are these days capable of performing an analysis of the
signal, and introducing and storing appropriate correctional offsets.

Other pots which may also be encountered are T.G(AIN) and F.G(AIN). These
set the operational gains of the tracking and focus servo loops. They are
often to still be found in modern players. Adjusting these up slightly, can
often improve a player with marginal performance, but if set too high,
particularly in the case of the focus servo, will result in the lens making
a mechanical 'hissing' noise, particularly on a marked or scuffed disc.

Finally, there is always a pot on the laser which sets its output power.
With a few notable exceptions such as Pioneer, this pot is sealed and MUST
NOT be adjusted. Even a small overdrive of the laser diode, can result in
its partial, or even complete destruction.

Arfa



Re: A problem with a cd player

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Yeah, OK Mark. CLV servo it is ! Just another senior moment. I seem to have
more of them these days ...         :-(

Still, the rest of what I said is valid.

Arfa



Re: A problem with a cd player
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I knew that you knew that. I was just foolin' around.

mz


Re: A problem with a cd player



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Yeah, I know that Mark. Dunno. The older I get, the more this nonsense seems
to just fly out of my mouth (fingers) ...  Perhaps I'm going down with some
kind of early addle-brain. There's a prog on the telly next week about poor
old Terry Pratchett. He first noticed something was wrong, when he kept
typing spelleen misstaykes   :-(     I think that my problem is that I spend
too much late-night time sitting in front of this idiot machine, instead of
getting some sleep ...

Arfa



Re: A problem with a cd player
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Same problem here. Gets frustrating at times. I'll stop mid-sentence because
I can't bring forth a noun to continue. Then after perhaps 2 or 3 seconds it
comes and I finish the sentence. Short-term memory getting worse also,
although in truth this has always been a weakness of mine. Still able to
function at work though, so that's a blessing.

My hearing is getting really bad also.

With me it's early morning. I get up around 3:30 to 4:00 AM most days.

Spend a lot of time perusing old analog meters etc on eBay. Added several to
my collection lately, including an AVO 8 which I got interested in after
finding you had one. It's a Mark 5 Nato model, on it's way from Germany as
we speak. Not many AVO's in the U.S. it turns out...

Added several Simpsons (the American answer to AVO?) lately as well. The guy
at simpson260.com has offered to sell me his 9 remaining Simpsons. I don't
think I can do that though, nowhere to put them!


Mark Z.


Re: A problem with a cd player
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Those large AVOs were to be found pretty well everywhere even vaguely
connected with electronics in the UK. Still available new up until
recently - at about $1000.
 My original one got stolen many years ago - and like many others I just
used a DVM instead. But always wanted another - and got a perfect
condition one off Ebay a few years ago. Nothing else quite matches the
tactile switches. ;-) And of course if working to old service sheets,
voltage measurements were near always made on one so allowed for the
loading.

--
*Horn broken. - Watch for finger.

    Dave Plowman         snipped-for-privacy@davenoise.co.uk           London SW
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Re: A problem with a cd player
On Fri, 30 Jan 2009 05:47:47 -0600, "Mark Zacharias"

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Old age sucks.

Re: A problem with a cd player

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Big time for sure. Thirty years ago, I thought I was immortal, and could
keep going for two or more days at a time without sleep. I just couldn't
figure how people could degenerate into the old farts that they did. Now I
am one, and I look at my daughter looking at me thinking "I just can't
figure ... "

Sigh ...          :-\

Arfa



Re: A problem with a cd player
snipped-for-privacy@ntlworld.com says...>
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You're still young.  Don't worry, as your daughter gets older,
you'll get wiser.  ;-)




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