explain this

[RichD]

I have an old portable CD player, still works.
Runs on 2 AA batteries.

The other day, a CD was skipping, on the third
track. I tolerated it for a minute, then forwarded.
Other tracks also damaged.

The battery charge indicator read zero. Dead
battery or smushy disc? I pop in another CD, works
fine. Try the bad CD again, same symptoms repeated.

How does a dodgy disc muck the battery charge
sensing circuit?

Sherlock Holmes, paging Detective Holmes, please
report to sci.elect.design -


--
Rich

[Ricky]

Did you try changing the batteries? Is it possible that one disc has something on it that takes more current than the other discs? Check the batteries.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

[Jan Panteltje]

On a sunny day (Sat, 28 Jan 2023 16:54:57 -0800 (PST)) it happened RichD
<r_dela...@yahoo.com> wrote in
<dcd6f2e6-9443-4c32...@googlegroups.com>:

>I have an old portable CD player, still works.
>Runs on 2 AA batteries.
>
>The other day, a CD was skipping, on the third
>track. I tolerated it for a minute, then forwarded.
>Other tracks also damaged.
>The battery charge indicator read zero. Dead
>battery or smushy disc? I pop in another CD, works
>fine. Try the bad CD again, same symptoms repeated.

So check CD for finger prints and dirt,
clean with dishwash detergent and lots of water
and use tissue paper to whipe it clean.
That is what I do,

If still bad .. try a better CD reader.
My LG Mdisc reader (in a PC) is good at reading stuff it seems.

>How does a dodgy disc muck the battery charge
>sensing circuit?

Motor speed control variations trying to re-read the same sectors?

[Martin Brown]

On 29/01/2023 00:54, RichD wrote:
> I have an old portable CD player, still works.
> Runs on 2 AA batteries.
>
> The other day, a CD was skipping, on the third
> track. I tolerated it for a minute, then forwarded.
> Other tracks also damaged.
>
> The battery charge indicator read zero. Dead
> battery or smushy disc? I pop in another CD, works
> fine. Try the bad CD again, same symptoms repeated.
>
> How does a dodgy disc muck the battery charge
> sensing circuit?

It doesn't. It makes the tracking servo work a lot harder drawing much
more current from the poor unfortunate "on their last legs" batteries.

In normal tracking it barely has to do much except constant velocity
movement with a slight wobble to handle any eccentricity of the mount
but with a scratched disk then all bets are off.

> Sherlock Holmes, paging Detective Holmes, please
> report to sci.elect.design -

--

Martin Brown

[Don]

Jan Panteltje wrote:

> RichD wrote:
>
>>I have an old portable CD player, still works.
>>Runs on 2 AA batteries.
>>
>>The other day, a CD was skipping, on the third
>>track. I tolerated it for a minute, then forwarded.
>>Other tracks also damaged.
>>The battery charge indicator read zero. Dead
>>battery or smushy disc? I pop in another CD, works
>>fine. Try the bad CD again, same symptoms repeated.
>
> So check CD for finger prints and dirt,
> clean with dishwash detergent and lots of water
> and use tissue paper to whipe it clean.
> That is what I do,
>
> If still bad .. try a better CD reader.
> My LG Mdisc reader (in a PC) is good at reading stuff it seems.

You may want to limit yourself to lens tissue. I personally always use a
soft cloth on all things optical - even plastic - to avoid minuscule
wood scratches from paper products.
Sometimes a simply different, and not necessarily better, CD reader
works for me. I surmise a different readers's optical alignment varies
slightly (while within tolerances) to track a random scratched CD more
optimally.

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

[Don Y]

On 1/29/2023 8:52 AM, Don wrote:
> You may want to limit yourself to lens tissue. I personally always use a
> soft cloth on all things optical - even plastic - to avoid minuscule
> wood scratches from paper products.
> Sometimes a simply different, and not necessarily better, CD reader
> works for me. I surmise a different readers's optical alignment varies
> slightly (while within tolerances) to track a random scratched CD more
> optimally.

Rip the original and put it away. (All of my music collection originals
reside in a set of boxes hiding under a bed; DVD originals on spindles
tucked in a clost)

Use the ripped (ISO on spinning rust or a real optical medium) "copy" until
*it* becomes unreadable.

I've noticed the local library has started doing this with purchased
materials -- even including the "dust jackets" (print a new copy
when the circulating copy gets lost or tattered)

[Jan Panteltje]

On a sunny day (Sun, 29 Jan 2023 09:32:40 -0700) it happened Don Y
<blocked...@foo.invalid> wrote in <tr6739$2r7um$1...@dont-email.me>:

>On 1/29/2023 8:52 AM, Don wrote:
>> You may want to limit yourself to lens tissue. I personally always use a
>> soft cloth on all things optical - even plastic - to avoid minuscule
>> wood scratches from paper products.
>> Sometimes a simply different, and not necessarily better, CD reader
>> works for me. I surmise a different readers's optical alignment varies
>> slightly (while within tolerances) to track a random scratched CD more
>> optimally.
>
>Rip the original and put it away. (All of my music collection originals
>reside in a set of boxes hiding under a bed; DVD originals on spindles
>tucked in a clost)
>
>Use the ripped (ISO on spinning rust or a real optical medium) "copy" until
>*it* becomes unreadable.

A good light proof CD box helps:
http://panteltje.com/pub/CD_box_IXIMG_0547.JPG
http://panteltje.com/pub/CD_box_binnenkant_IXIMG_0549.JPG
Is full now, 1000 CDs.. CD-R.. CD-RW .. Bluray
Disks are numbered from 1 to 1000
There is one big text file that has an entry for each one,
what it contains, how it was made and how to read it, for example:

927
BD-R-25
Platinum 4x inkjet printable
LG BH10LS38
ext2 filesystem
Raspberry debian 8 GB SDcard image with librtlsdr, xforms, fftw3, xpsa, dump1090
Risc OS image
Original debian image
Method:
dd if=/dev/zero bs=1000000000 count=25 > bluray.iso
mke2fs bluray.iso
mount -o loop=/dev/loop0 bluray.iso /mnt/loop
cp ... /mnt/loop/
# stay below about 22.3 GB
du /mnt/loop
umount /dev/loop0
growisofs -speed=4 -dvd-compat -Z /dev/dvd=bluray.iso
# l /mnt/loop
total 13882600
drwx------ 2 root root 16384 Feb 2 17:55 lost+found/
-rw-r--r-- 1 root root 1939865600 Feb 9 04:44 2013-02-09-wheezy-raspbian.img
-rw-r--r-- 1 root root 159063 Mar 6 13:56 Raspberry-Pi-R2.0-Schematics-Issue2.2_027.pdf
-rw-r--r-- 1 root root 109401 Mar 6 13:59 RPi_Low-level_peripherals.html
drwxr-xr-x 2 root root 4096 Mar 6 13:59 RPi_Low-level_peripherals_files/
-rw-r--r-- 1 root root 229735 Mar 6 14:01 bcm2835-1.22.tar.gz
-rw-r--r-- 1 root root 102683388 Mar 8 15:27 riscos-2012-11-01-RC6.zip
-rw-r--r-- 1 root root 42 Mar 8 15:30 sha1sum_riscos-2012-11-01-RC6.zip.txt
-rw-r--r-- 1 root root 42 Mar 10 13:26 sha1_sum_rasbian_zip
-rw-r--r-- 1 root root 41 Mar 10 13:41 sha1sum_2013-02-09-wheezy-raspbian.img.txt
-rw-r--r-- 1 root root 1590 Mar 10 16:17 how_to_raspberry.txt~
-rw-r--r-- 1 root root 1590 Mar 10 16:17 how_to_raspberry.txt
-rw-r--r-- 1 root root 8193572864 Mar 10 17:16 raspberry_with_rtlsdr_xpsa.img
-rw-r--r-- 1 root root 3965190144 Mar 10 17:36 media_4GB_sdcard.img
-rw-r--r-- 1 root root 41 Mar 10 17:38 sha1sum_raspberry_with_rtlsdr_xpsa.img.txt
-rw-r--r-- 1 root root 41 Mar 10 17:39 sha1sum_media_4GB_sdcard.img



So basically in that case I just make an empty file of the right size,
put a filesystem on that file,
copy all stuff I want to keep to that file
and use it as image that I then burn to the disk.
mount -o loop can then load the disk and you have a directory with all your stuff
Linux of course

Sometimes I just write stuff as image... movies too.
94
Nashua slimline 4x
DVD+RW
MASTER SOURCE as image
Use tar -zxvf /dev/dvd in /video to unpack
Very long list of what is in the tgz follows this entry
...
...

Everything in UNIX is a file after all,

There is more....
So far data retention is impeccable,
main way to keep the written disks: Keep It In The Dark.
It is the same thing as with old film camera and exposure
time * light intensity does it.
If you leave your burned disk on the bookshelf in the sun you get data errors after 2 hours,
Tried that
Keep it in the dark and > 20 years is no problem.

[Clifford Heath]

On 30/01/23 02:52, Don wrote:
> Jan Panteltje wrote:
>> RichD wrote:
>>> I have an old portable CD player, still works.
>>> Runs on 2 AA batteries.
>>>
>>> The other day, a CD was skipping, on the third
>>> track. I tolerated it for a minute, then forwarded.
>>> Other tracks also damaged.
>>> The battery charge indicator read zero. Dead
>>> battery or smushy disc? I pop in another CD, works
>>> fine. Try the bad CD again, same symptoms repeated.
>>
>> So check CD for finger prints and dirt,
>> clean with dishwash detergent and lots of water
>> and use tissue paper to whipe it clean.
>> That is what I do,
>>
>> If still bad .. try a better CD reader.
>> My LG Mdisc reader (in a PC) is good at reading stuff it seems.
>
> You may want to limit yourself to lens tissue. I personally always use a
> soft cloth on all things optical - even plastic - to avoid minuscule
> wood scratches from paper products.

Exactly; wood products (even the softest of tissues) contain silica
particles that will scratch any glass. Enough repetitions of
sub-wavelength scratches eventually produces visible artefacts.

Clifford Heath

[Jan Panteltje]

On a sunny day (Mon, 30 Jan 2023 10:28:42 +1100) it happened Clifford Heath
<no....@please.net> wrote in
<173eeb638870abde$1$2212660$9aa1...@news.thecubenet.com>:

Nope
Using the same soft cloth over and over again accumulates dirt and particles on it,
exactly what you do not want.
Simple tissiue paper you throw away (I hope ;-) ) after use, and take a clean one
for the next job.
How often do you clean your CDs etc? once clean keep fingers of it.
I use this method to clean my reading glasses too, using warm water,
that removes any fat etc.
Never noticed a problem, always very clean.
If you have a lens with expensive coating maybe not.
But OTOH my Xiaomi smartphone's 48 megapixel camera still gives very good pictures
without me ever having cleaned the lens,
My Canon camera lens I have never cleaned I think, have taken it 100% apart though
once to fix something.
Webcams, never needed cleaning, security cams neither..
CDs etc fingerprints mostly.

[Don]

Jan Panteltje wrote:

I instinctively use a /freshly laundered/ cloth to clean the coating on
my expensive eyeglasses and other optical surfaces. Because, as you
insinuate, a dirty used cloth leaves smudges behind.
Yes, it is indeed interesting how outside security cameras exposed
to the weather never need to be cleaned. Nor does my old "not a Nikon"
SLR Pentax camera. The "fingerprint factor," so to speak, must explain
it.
Anyhow, my easy-to-use phone camera seems to be pushing the old
Pentax into retirement. About a decade ago one of my clients told me how
patent protection for imagery used in satellites and other expensive
endeavors was set to expire soon and thereby release the technology to
the masses.

[RichD]

On January 29, Jan Panteltje wrote:
>> I have an old portable CD player, still works.
>> Runs on 2 AA batteries.
>>The other day, a CD was skipping, on the third

>> track. Other tracks also damaged.

>> The battery charge indicator read zero. Dead
>> battery or smushy disc? I pop in another CD, works
>> fine. Try the bad CD again, same symptoms repeated.

>> How does a dodgy disc muck the battery charge
>> sensing circuit?
>
> Motor speed control variations trying to re-read the same sectors?

That appears to be the case.
But it doesn't compute. If a sector is unreadable, the head should
remain on that track, with repeated attempts, constant speed.
What causes motor speed variations?

--
Rich

[Jan Panteltje]

On a sunny day (Mon, 30 Jan 2023 10:43:48 -0800 (PST)) it happened RichD
<r_dela...@yahoo.com> wrote in
<45e2ee6f-a037-4c1b...@googlegroups.com>:

I have the impression, from the sound, that my LG drive
reduces speed when an error is encountered to read it again at lower speed,
and then speeds up again,
could also be waiting when cache full etc..

My drives do a whole number when starting to read a CD,
may take much longer if errors found,
Did read in a few more disks to my 1 TB USB stick yesterday..