February 24th 16, 07:12 AM
posted to uk.rec.audio
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Quad FM4 Battery
"Johnny B Good" wrote in message
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On Sat, 20 Feb 2016 04:40:14 -0800, Phil Allison wrote:
RJH wrote:
Phil is right but I would wait until you have extracted it
before
buying a replacement as it could be Ni-Cad or Ni-MH depending on
the
age of the tuner, and they require slightly different charging
regimes. Equally it could be 3V, 3.6V or 4.8V although I would
admit
that the size suggests the latter.
** AFAIK, Quad FM4s only ever used 4.8V NiCd battery packs with
four
cells specially made for memory back-up. It was trickle charged at
a few
mA whenever the tuner was powered up.
I doubt any re-engineering is needed to employ a four cell NiMH
pack
instead.
Agreed, In fact, when I was looking for a replacement 3 cell NiCd
for a
Potterton 2000 CH program controller, they'd changed to a larger
capacity
NiMH version. Oddly, the tagless drop in batteries used by this
programmer were over twice the price of the solder tagged ones.
Naturally, I bought the cheaper tagged battery and pulled the tags
off
and dressed the 'pips' with a fine file to recreate the plug in
version
at less than half price for less than ten minutes of D-I-Y activity.
:-)
The 4.8 volts seems unusually high for battery backed memory though.
The
more usual with static cmos ram being 3.6 volts. CMOS sram is
guaranteed
to retain data integrity right down to the 2 volt point - and that
includes the RTCs with their 70 8 bit registers 'going spare' as
used by
IBM in their AT PCs first marketed back in August 1984).
--
Quad list it as a 4V battery - quite how they achieve that is another
question altogether!
--
Woody
harrogate3 at ntlworld dot com
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February 26th 16, 01:48 AM
posted to uk.rec.audio
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Quad FM4 Battery
On Wed, 24 Feb 2016 08:12:11 +0000, Woody wrote:
"Johnny B Good" wrote in message
...
On Sat, 20 Feb 2016 04:40:14 -0800, Phil Allison wrote:
RJH wrote:
Phil is right but I would wait until you have extracted it before
buying a replacement as it could be Ni-Cad or Ni-MH depending on
the age of the tuner, and they require slightly different charging
regimes. Equally it could be 3V, 3.6V or 4.8V although I would
admit that the size suggests the latter.
** AFAIK, Quad FM4s only ever used 4.8V NiCd battery packs with four
cells specially made for memory back-up. It was trickle charged at a
few mA whenever the tuner was powered up.
I doubt any re-engineering is needed to employ a four cell NiMH pack
instead.
Agreed, In fact, when I was looking for a replacement 3 cell NiCd for a
Potterton 2000 CH program controller, they'd changed to a larger
capacity NiMH version. Oddly, the tagless drop in batteries used by
this programmer were over twice the price of the solder tagged ones.
Naturally, I bought the cheaper tagged battery and pulled the tags off
and dressed the 'pips' with a fine file to recreate the plug in version
at less than half price for less than ten minutes of D-I-Y activity.
:-)
The 4.8 volts seems unusually high for battery backed memory though.
The more usual with static cmos ram being 3.6 volts. CMOS sram is
guaranteed to retain data integrity right down to the 2 volt point -
and that includes the RTCs with their 70 8 bit registers 'going spare'
as used by IBM in their AT PCs first marketed back in August 1984).
--
Quad list it as a 4V battery - quite how they achieve that is another
question altogether!
It might be the charger's nominal upper voltage limit for a 3 cell NiCd
(blue) or 3 cell NiMH (green) battery. Constant current charging of
either type results in a 'resting voltage' immediately after going off
charge in the region of 1.4 volts per cell, usually dropping to 1.36
volts after a day or two. The 1.2 volts rating for these cells is the
minimum voltage just prior to becoming exhausted of useful charge.
It's quite likely that a very simple blocking diode and current limiting
resistor charging circuit fed off the 5v logic supply is all that's being
used to keep the battery charged up just like the arrangement used on
early pre-Pentium PC motherboards to maintain the RTC battery backup
(typically a 3 cell 60mAH NiCd soldered onto the board).
If needs must, you could replace it with a lithium primary cell (3.1v)
and snip the resistor lead to disable the charging. Those CR2032 180mAH
coin cells now commonly used in PCs will keep the RTC running for
anywhere from 18 months in the case of the ****e PC Chips branded
motherboards right up to 5 years or more on the better quality brands of
motherboard. If you wire in one of those "Half AA" Lithium 'batteries' so
favoured by the manufacturers of smoke detectors guaranteed to last ten
years on their soldered in battery, I should imagine it will last a
couple of decades at least.
--
Johnny B Good
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March 2nd 16, 05:04 PM
posted to uk.rec.audio
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Quad FM4 Battery
On 26/02/2016 18:55, Woody wrote:
"RJH" wrote in message
...
On 26/02/2016 07:02, Phil Allison wrote:
Johnny B Good wrote:
Quad list it as a 4V battery - quite how they achieve that is
another
question altogether!
** Quad have " 4.8V NiCd " printed on the schem next to it.
It might be the charger's nominal upper voltage limit for a 3 cell
NiCd
(blue) or 3 cell NiMH (green) battery. Constant current charging
of
either type results in a 'resting voltage' immediately after going
off
charge in the region of 1.4 volts per cell, usually dropping to
1.36
volts after a day or two. The 1.2 volts rating for these cells is
the
minimum voltage just prior to becoming exhausted of useful charge.
** The rest voltage of a NiCd cell is 1.25V - under a moderate load
it drops to 1.2v and is exhausted at 1.1V.
When trickle charged in memory back up use, there is just enough
charge to compensate for internal self discharge - normally about
C/50. So for a nominal 150mAh cell, that equates to a 3mA trickle
charge.
A good condition, 4 cell pack ought to measure between 4.8 and 5V.
This one reads 4.6V.
I've been in touch with the seller. I've had a couple of messages.
Last week's was 'I'll sort it next week'. This week's is the same
;-)
It turns out that he hasn't (he says) used the tuner for some years.
The truth will out...............
I wish. At first he admitted (by email) that he hadn't used the tuner
for some time - 'forgotten when I last used it'. Now he's adamant that
it worked at the time of sale. He's willing to give me a £30 refund, but
I'm not overly happy about that so I may take it to the ebay dispute
thingy. Problem being I can't prove either way, it may have taken a
knock in transit - although his dishonesty is now on record, so that
might help.
On the up-side, had an email from Quad - £48 plus VAT fixed labour
charge, plus parts and postage, to 'full working specification'. That
seems like a very good deal, so I may take them up on that.
Still a bit cross that I paid for a 'very nice' FM4.
--
Cheers, Rob
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March 2nd 16, 08:33 PM
posted to uk.rec.audio
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Quad FM4 Battery
The truth will out...............
I wish. At first he admitted (by email) that he hadn't used the tuner
for some time - 'forgotten when I last used it'. Now he's adamant that
it worked at the time of sale. He's willing to give me a £30 refund, but
I'm not overly happy about that so I may take it to the ebay dispute
thingy. Problem being I can't prove either way, it may have taken a
knock in transit - although his dishonesty is now on record, so that
might help.
On the up-side, had an email from Quad - £48 plus VAT fixed labour
charge, plus parts and postage, to 'full working specification'. That
seems like a very good deal, so I may take them up on that.
That is a very good deal!...
Still a bit cross that I paid for a 'very nice' FM4.
What was actually wrong with it again?..
--
Tony Sayer
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