Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old January 8th 21, 11:53 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On Fri, 8 Jan 2021 13:54:04 -0800 (PST), "
wrote:

Generally speaking, I've found that supercaps used as memory devices are generally run *very* close to their voltage rating, so if your supercap is a 2.7V, there's a good chance there could be 2.5 volts on it. But, you don't need to make this complicated. Plug the radio in and see what the voltage is across the supercap. Most of the supercaps I've changed just go low value/high ESR and don't short. Whatever the voltage is under test, add that via cell. Since the value you need is unlikely (Murphy's Law) to be a direct value of a cell you want to add, you may have to add more than one diode to drop the voltage to or even a bit below the memory voltage.


Thanks! Just the kind of details I wanted. Must admit I hadn't thought
about using diodes to 'trim' the cell(s) to the correct voltage.

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Old January 9th 21, 03:23 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On Thu, 07 Jan 2021 23:35:36 +0000, Cursitor Doom
wrote:

On Thu, 07 Jan 2021 13:33:31 -0500, legg wrote:

On Wed, 06 Jan 2021 20:51:28 +0000, Cursitor Doom
wrote:

On Wed, 06 Jan 2021 13:44:19 -0600, Chuck
wrote:

On Wed, 06 Jan 2021 18:00:32 +0000, Cursitor Doom
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.

At that value it would be a supercapacitor I'd imagine. Were they
installing those in new equipment 10 years ago?


They were showing up as surplus 20 years ago.

RL



Well I can't understand in that case why there are so few of them
listed on Ebay currently. I may have to imrovise here and go back to
my initial idea of using a lithium button cell in series with a diode
to prevent it being charged.

Anyone see any issues with that approach?


Do you know what the original back-up source is, yet?

You were just looking at it, in the last report.

You should be able to do a simple repair, without a lot
of useless speculation.

RL
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Old January 9th 21, 05:20 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On 1/9/21 8:23 AM, legg wrote:
You should be able to do a simple repair, without a lot
of useless speculation.

RL


You forget who we're dealing with.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
  #24   Report Post  
Old January 9th 21, 08:21 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On Sat, 09 Jan 2021 09:23:26 -0500, legg wrote:

On Thu, 07 Jan 2021 23:35:36 +0000, Cursitor Doom
wrote:

On Thu, 07 Jan 2021 13:33:31 -0500, legg wrote:

On Wed, 06 Jan 2021 20:51:28 +0000, Cursitor Doom
wrote:

On Wed, 06 Jan 2021 13:44:19 -0600, Chuck
wrote:

On Wed, 06 Jan 2021 18:00:32 +0000, Cursitor Doom
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.

At that value it would be a supercapacitor I'd imagine. Were they
installing those in new equipment 10 years ago?

They were showing up as surplus 20 years ago.

RL



Well I can't understand in that case why there are so few of them
listed on Ebay currently. I may have to imrovise here and go back to
my initial idea of using a lithium button cell in series with a diode
to prevent it being charged.

Anyone see any issues with that approach



Do you know what the original back-up source is, yet?


No I don't! I've had it apart just a few moments ago. So far I have
found NO supercaps. One of the ordinary electros 220uF tested over 5
ohms ESR so I'm going to replace that, but I very much doubt that's
anything to do with the fault in question.

You were just looking at it, in the last report.

You should be able to do a simple repair, without a lot
of useless speculation.


IME there's *rarely* any such thing!

I'll post some photos of the internals shortly....
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Old January 9th 21, 08:49 PM posted to sci.electronics.repair
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Default Finding the cmos battery

Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?


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Old January 9th 21, 11:12 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On Sat, 09 Jan 2021 19:49:21 +0000, Cursitor Doom
wrote:

Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?


Look at the actual board with the memory on it?

RL
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Old January 9th 21, 11:26 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On Sat, 09 Jan 2021 17:12:36 -0500, legg wrote:

On Sat, 09 Jan 2021 19:49:21 +0000, Cursitor Doom
wrote:

Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?


Look at the actual board with the memory on it?

RL


Good steer. Unfortunately this is the most inaccessible of the lot;
sandwiched up against the top display module it's impossible to see
what's in there without further disassembly. But now you have
suggested it, I think there's no other obvious course of action here.

Am I still looking solely for a supercap?

  #28   Report Post  
Old January 9th 21, 11:48 PM posted to sci.electronics.repair
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Default Finding the cmos battery

On 09.01.21 20:49, Cursitor Doom wrote:
Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?

Yes. Use a valid,working photo website instead of the crap site.
  #29   Report Post  
Old January 10th 21, 01:11 AM posted to sci.electronics.repair
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Default Finding the cmos battery

On Sat, 09 Jan 2021 22:26:29 +0000, Cursitor Doom
wrote:

On Sat, 09 Jan 2021 17:12:36 -0500, legg wrote:

On Sat, 09 Jan 2021 19:49:21 +0000, Cursitor Doom
wrote:

Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?


Look at the actual board with the memory on it?

RL


Good steer. Unfortunately this is the most inaccessible of the lot;
sandwiched up against the top display module it's impossible to see
what's in there without further disassembly. But now you have
suggested it, I think there's no other obvious course of action here.

Am I still looking solely for a supercap?


If it, or a battery, is there, it will be obvious and likely mounted
on the through-hole side of the board.

Niether are small parts, just low profile.

RL
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Old January 10th 21, 01:44 AM posted to sci.electronics.repair
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Default Finding the cmos battery

On Sat, 09 Jan 2021 19:11:53 -0500, legg wrote:

On Sat, 09 Jan 2021 22:26:29 +0000, Cursitor Doom
wrote:

On Sat, 09 Jan 2021 17:12:36 -0500, legg wrote:

On Sat, 09 Jan 2021 19:49:21 +0000, Cursitor Doom
wrote:

Here's some photos of the insides:

https://yandex.com/collections/user/...M0MzZmMw%3D%3D


Any suggestions?

Look at the actual board with the memory on it?

RL


Good steer. Unfortunately this is the most inaccessible of the lot;
sandwiched up against the top display module it's impossible to see
what's in there without further disassembly. But now you have
suggested it, I think there's no other obvious course of action here.

Am I still looking solely for a supercap?


If it, or a battery, is there, it will be obvious and likely mounted
on the through-hole side of the board.

Niether are small parts, just low profile.


OK, got it, thanks.I'll investigate further tomorrow..........


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