explain this

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

On a sunny day (Mon, 30 Jan 2023 10:43:48 -0800 (PST)) it happened RichD
<r_delaney2001@yahoo.com> wrote in
<45e2ee6f-a037-4c1b-ba3f-88f446dc993en@googlegroups.com>:

>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?

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..