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Subject: Re: Backlight on recorder dimming?
From: e-potis (geokonst_at_hol.gr)
Date: 2003-01-06


Mine (pretty new) dims too but till now i thought that it was supposed to.
It looks like the cool effect some cell phones have. Like it though it
doesn't work all the time

----- Original Message -----
From: <for_spam_at_gmx.de>
Newsgroups: gmane.comp.systems.archos.rockbox.general
Sent: Monday, January 06, 2003 8:14 PM
Subject: RE: Backlight on recorder dimming?

Hey Rockboxers,

maybe there are some ajb`s out "in the wild" which have this dimming feature
-
perhaps it`s a feature not meant for "public usage" - but maybe some "tuned"
or
"pre series" jukeboxes spuriously excaped from the archos development
department
for some reason ???

I think that the dimming effect, MOST people realize is due to the voltage
drop
of the batteries, when hhd spins up.

But:
> Even when the disk is not spinning, spinning up, or spinning down, I can
> press the volume up/down (other buttons work but I will go with this
example)
> button and the back light will come on and after 4s (the time I have it
set for)
> it will get slightly brighter, and then get progressively dimmer and
dimmer until
> the LEDs are off. Off to the best my feeble optic nerve can determine. I
am
> willing to crack it open and stick the backlight on the oscope and see
what truly is
> happening.

indeed, this is strange !
Perhaps, we should collect some information:
- what exact jb model ?
- where and when was it bought ?
- when/how does it happen ?

regards
Roland

> Hey all,
>
> I had a similar revelation when I had my problems with the short in the
> Archos... I noticed that there were two discreet backlight luminosities.
> I
> haven't received my JB back from Archos tech support (where, oh where, has
> my little Archos gone!) so I can't substantiate that it's supposed to or
> not. I noticed a definite difference when I pressed "up" (towards the
> face)
> on the DC power in jack, and I *think* the display got brighter when I
> plugged it in. [The problem I had was a physical short somewhere in the
> power circuitry which prevented the device from operating properly unless
> the DC power was plugged in AND a physical pressure was put on the device
> to
> alleviate the short or whatever it was.]
>
> I had originally thought that perhaps the display had two settings - one
> for
> low-power, one for higher-power (similar to many other devices) that gave
> a
> brighter LCD output when an external power source was applied. On further
> reflection, I'm not so sure, but that may very well be the case. (i.e.,
> when the HDD spins up, the LCD drops into a lower-power mode to give more
> to
> the HDD or what not.)
>
> Does that sound consistent with anyone else's experience?
>
> Matt
>
> -----Original Message-----
> From: owner-rockbox_at_cool.haxx.se [mailto:owner-rockbox_at_cool.haxx.se]On
> Behalf Of Chris Muth
> Sent: Tuesday, December 31, 2002 2:41 AM
> To: rockbox_at_cool.haxx.se
> Subject: Re:Backlight on recorder dimming?
>
>
> Hey,
>
> I too have noticed that the backlight will dim slightly when the disk
> spins
> up.
> I have also noticed that backlight will get slightly brighter when I apply
> pressure to the
> face plate. This is almost certainly a physical thing. Perhaps the light
> spreader is getting
> closer to the LED array and therefore the uneven propagation pattern ot
> the
> light being emitted by
> the diode is focused in such a way to provide more light? [Chris is just
> thinking into the keyboard]
> That is not a big deal and is beside the point.
>
> Even when the disk is not spinning, spinning up, or spinning down, I can
> press the
> volume up/down (other buttons work but I will go with this example) button
> and the
> back light will come on and after 4s (the time I have it set for) it will
> get slightly brighter,
> and then get progressively dimmer and dimmer until the LEDs are off. Off
> to
> the best my
> feeble optic nerve can determine. I am willing to crack it open and stick
> the backlight on the
> oscope and see what truly is happening.
>
> Being that this is a digital device, I am guessing that there will be many
> discrete voltage levels going
> into the backlight, and not random rail noise that would suggest that the
> disk is putting noise on the
> power rail.
>
> Thank You for the responses.
>
> Best Regards,
> Chris Muth <muthchris_at_muth.cc>
>
> >Andreas Stemmer <Andreas.Stemmer_at_web.de> wrote:
> >I had the same impression with my AJBR20: the backlight dims when the
> >harddisc spins up because there's not enough power provided. If you want
> to
> >program some dimming effects, you could use very fast on/off switching
> >(pulse width modulation) which works quite well with any led like the
> >backlight leds.
> >
> >Andreas Stemmer
> >
> >> >>I think the dimming is pretty cool, I just can't figure out why if
> >appears
> >> to get yellow and
> >> >>I can't quite figure out what determines whether it dims or just goes
> >off.
>
>

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