Digest for sci.electronics.repair@googlegroups.com - 13 updates in 3 topics

8:40 AM Penedão
Cursitor Doom <cd@noreply.com>: Jan 06 06:00PM

Hi all,
 
I have a Roberts Stream 105 internet radio which I bought about 9
years ago. It's been fine up until maybe 18 months ago when it could
no longer remember my preferred settings. I'm guessing it has a little
backup cell in there somewhere that's gone way past its sell-by date.
I've opened up the case and it must be very well hidden indeed. I
asked Roberts for info on where it is but they obfuscated and told me
to return it to them and they'd fix it for 40 quid! There are no
manuals for this model on line (not service manuals anyway) and I *do*
like to fix things for myself as a matter of course anyway. The inside
consists of only 3 boards apart from the display: an audio board (as
it describes itself) the wireless card (I deduce from the fact that
although it's fully screened it's got a MAC address label on it) and
controller board interfacing to the user controls.
The only place this battery could be hiding is within a screened
enclosure on the "audio board". Now, I should have done this sooner
obviously, but time shortages and whatnot, I've probed the underside
of the screened area and found a persistent 0.3V above ground on some
of the joints. Does that sound like the sort of voltage a backup cell
would fall back to after 9 years? This 0.3V is with all external power
removed and after shorting out any capacitances.
"Peter W." <peterwieck33@gmail.com>: Jan 06 10:40AM -0800

My guess is that it is a 2032 button cell - which have been popular for that function for a long time. Are you able to apply about 3V at the appropriate polarity and see if the memory comes back? Or even 1.5V as proof-of-concept?
 
After which comes the question of whether it is rechargeable (LIR2032) or not (CR2032).
 
Peter Wieck
Melrose Park, PA
Cursitor Doom <cd@noreply.com>: Jan 06 07:00PM

On Wed, 6 Jan 2021 10:40:30 -0800 (PST), "Peter W."
 
>My guess is that it is a 2032 button cell - which have been popular for that function for a long time. Are you able to apply about 3V at the appropriate polarity and see if the memory comes back? Or even 1.5V as proof-of-concept?
 
>After which comes the question of whether it is rechargeable (LIR2032) or not (CR2032).
 
I was thinking *if* it is rechargeable, I *could* (could I not?)
replace with an equivalent non-rechargeable in series with a diode to
prevent it from taking a charge it's not designed for?
Chuck <chuck23@dejanews.net>: Jan 06 01:44PM -0600

On Wed, 06 Jan 2021 18:00:32 +0000, Cursitor Doom <cd@noreply.com>
wrote:
 
>of the joints. Does that sound like the sort of voltage a backup cell
>would fall back to after 9 years? This 0.3V is with all external power
>removed and after shorting out any capacitances.
Look for a 1/2 to1 farad electrolytic capacitor. Probably near the
upc.
Cursitor Doom <cd@noreply.com>: Jan 06 08:48PM

On Wed, 06 Jan 2021 12:56:07 -0700, KenW
>>upc.
 
>Caps were used to retain voltage to a circuit. Some telephone systems
>I worked on used them.
 
What? Are you guys saying there may be no actual battery at all? And
they've used an electro in place of one?
Cursitor Doom <cd@noreply.com>: Jan 06 08:51PM

On Wed, 06 Jan 2021 13:44:19 -0600, Chuck <chuck23@dejanews.net>
wrote:
 
>>removed and after shorting out any capacitances.
>Look for a 1/2 to1 farad electrolytic capacitor. Probably near the
>upc.
 
At that value it would be a supercapacitor I'd imagine. Were they
installing those in new equipment 10 years ago?
"ohg...@gmail.com" <ohger1s@gmail.com>: Jan 06 12:51PM -0800

On Wednesday, January 6, 2021 at 3:49:00 PM UTC-5, Cursitor Doom wrote:
> >I worked on used them.
 
> What? Are you guys saying there may be no actual battery at all? And
> they've used an electro in place of one?
 
I remember several consumer electronic items using a "supercap", something like 0.47F. They did go bad certainly.
Chuck <chuck12@deja.net>: Jan 06 09:40PM -0600

Cursitor Doom <cd@noreply.com> Wrote in message:r
> On Wed, 06 Jan 2021 12:56:07 -0700, KenW<ken1943@invalid.net> wrote:>On Wed, 06 Jan 2021 13:44:19 -0600, Chuck <chuck23@dejanews.net>>wrote:>>>On Wed, 06 Jan 2021 18:00:32 +0000, Cursitor Doom <cd@noreply.com>>>wrote:>>>>>Hi all,>>>>>>I have a Roberts Stream 105 internet radio which I bought about 9>>>years ago. It's been fine up until maybe 18 months ago when it could>>>no longer remember my preferred settings. I'm guessing it has a little>>>backup cell in there somewhere that's gone way past its sell-by date.>>>I've opened up the case and it must be very well hidden indeed. I>>>asked Roberts for info on where it is but they obfuscated and told me>>>to return it to them and they'd fix it for 40 quid! There are no>>>manuals for this model on line (not service manuals anyway) and I *do*>>>like to fix things for myself as a matter of course anyway. The inside>>>consists of only 3 boards apart from the display: an audio board (as>>>it describes itself) the wireless card (I deduce from the fact that>>>although it's fully screened it's got a MAC address label on it) and>>>controller board interfacing to the user controls.>>>The only place this battery could be hiding is within a screened>>>enclosure on the "audio board". Now, I should have done this sooner>>>obviously, but time shortages and whatnot, I've probed the underside>>>of the screened area and found a persistent 0.3V above ground on some>>>of the joints. Does that sound like the sort of voltage a backup cell>>>would fall back to after 9 years? This 0.3V is with all external power>>>removed and after shorting out any capacitances.>>Look for a 1/2 to1 farad electrolytic capacitor. Probably near the>>upc.>>Caps were used to retain voltage to a circuit. Some telephone systems>I worked on used them.What? Are you guys saying there may be no actual battery at all? Andthey've used an electro in place of one?
 
The .47 to 1F caps have been used for 30 years in stereo receivers.
--
Cursitor Doom <cd@noreply.com>: Jan 07 02:26PM

On Wed, 6 Jan 2021 21:40:39 -0600 (CST), Chuck <chuck12@deja.net>
wrote:
 
>The .47 to 1F caps have been used for 30 years in stereo receivers.
 
I'm suitably amazed. Mind you I've never had much to do with them.
Clifford Heath <no.spam@please.net>: Jan 07 02:15PM +1100

On 6/1/21 11:30 pm, J.B. Wood wrote:
>> an omni (isotropic) antenna having gain of 0dB.
 
> Please look up what "isotropic" means and how it applies in antenna
> theory.  Then you'll be better informed.  Sincerely,
 
Smart-arses trying to explain why omni doesn't actually mean omni...
sigh. Some people are just born to be d*ckheads
"J.B. Wood" <arl_123234@hotmail.com>: Jan 07 09:22AM -0500

On 1/6/2021 10:15 PM, Clifford Heath wrote:
 
> Smart-arses trying to explain why omni doesn't actually mean omni...
> sigh. Some people are just born to be d*ckheads
 
An antenna is termed omni-directional if it possesses a circular
radiation pattern in the azimuthal plane. The same pattern in the
elevation plane can be doughnut-shaped or something else. An isotropic
antenna is a theoretical construct with a spherical pattern in 3-space.
As its pattern is spherical, it's useful as a basis for comparison of
antenna gain (azimuth & elevation). Gain expressed in "dBi" designates
the units for this comparison. An isotropic antenna can be approached
in practice using 3 orthogonal electrically-small (in terms of a
wavelength) dipoles or loops (often called "magnetic" loops by ham radio
operators). Sincerely,
 
--
J. B. Wood e-mail: arl_123234@hotmail.com
KenW <ken1943@invalid.net>: Jan 06 12:56PM -0700

On Wed, 06 Jan 2021 13:44:19 -0600, Chuck <chuck23@dejanews.net>
wrote:
 
>>removed and after shorting out any capacitances.
>Look for a 1/2 to1 farad electrolytic capacitor. Probably near the
>upc.
 
Caps were used to retain voltage to a circuit. Some telephone systems
I worked on used them.
 
 
KenW
KenW <ken1943@invalid.net>: Jan 06 03:14PM -0700

>What? Are you guys saying there may be no actual battery at all? And
>they've used an electro in place of one?
 
Very possible
 
 
KenW
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