Toshiba TV29C90 problem; Image fades to black...

[Dave Platt]

Could I even leave them in the nicad charger to stay fresh?

No. I wouldn't do this unless the charger were specifically designed for it.

NiMH cells show a voltage drop at full charge -- and require a heavy charge
to reach that point. It's unlikely a nicad charger would shut off at the
right point.

You're right. Although NiCd cells do have a voltage dropoff at full
charge, it's more pronounced than in a NiMH. A charger originally
designed for NiCd cells may wait until the voltage drops off
significantly (negative-delta-V) before terminating the charge. By
this point, a NiMH will have been significantly over-charged, which
isn't good for it.

NiMH battery manufacturers tend to use a dual cutoff approach - shut
off when the cell temperature starts rising, or at zero-delta-V.

I don't think NiMH cells are bothered by a trickle charge.

Depends on the charge level. A slow-charge rate (say, C/10 or C/20)
in an "overnight" charger may overcharge the NiMH cell if left
connected indefinitely.

A very low (e.g. C/100 or so) charge rate seems to be safe, I gather,
but it's also rather ineffective for NiMH cells - they have a poor
"charge acceptance" at low charge rates, and most of the power just
turns into heat.

The battery manuals I've read say that if you do decide to use a
maintenance charge (to keep the cells charged up indefinitely), what
works best is a pulse-charging technique. Hit 'em with a brief pulse
of current at a high rate (C or C/2 or so) every once in a while, and
let them rest between pulses. Time the pulses so that the total
charge delivered averages out to around 1-2% of their rated capacity
per day. This should keep them topped up (countering their tendency
to self-discharge) without overcharging them.

You should get NiMH cells with at least 2500mAh capacity. They're not
expensive. I also recommend the Maha/Powerex MH-C9000 charger.

For batteries which will be charged up, and then discharged heavily
within a few days to a week, that's good advice. Ditto if you're
planning to keep them hooked to a properly-designed maintenance charger.

For batteries that you're planning to charge, and then leave on the
shelf (or in equipment) for weeks at a time, I think it's better to go
with the new style of "ultra-low self discharge" NiMH cells - Sanyo
Eneloops, or Powerex Immedions, or Hybrios, or types of that sort.
Their rated capacity is lower (2000-2100 mAh), but unlike the older
style of NiMH they'll hold most of their charge for months.

I second the recommendation for the MH-C9000. A very neat piece of kit.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Dave Platt]

Could I even leave them in the nicad charger to stay fresh?

No. I wouldn't do this unless the charger were specifically designed for it.

NiMH cells show a voltage drop at full charge -- and require a heavy charge
to reach that point. It's unlikely a nicad charger would shut off at the
right point.

You're right. Although NiCd cells do have a voltage dropoff at full
charge, it's more pronounced than in a NiMH. A charger originally
designed for NiCd cells may wait until the voltage drops off
significantly (negative-delta-V) before terminating the charge. By
this point, a NiMH will have been significantly over-charged, which
isn't good for it.

NiMH battery manufacturers tend to use a dual cutoff approach - shut
off when the cell temperature starts rising, or at zero-delta-V.

I don't think NiMH cells are bothered by a trickle charge.

Depends on the charge level. A slow-charge rate (say, C/10 or C/20)
in an "overnight" charger may overcharge the NiMH cell if left
connected indefinitely.

A very low (e.g. C/100 or so) charge rate seems to be safe, I gather,
but it's also rather ineffective for NiMH cells - they have a poor
"charge acceptance" at low charge rates, and most of the power just
turns into heat.

The battery manuals I've read say that if you do decide to use a
maintenance charge (to keep the cells charged up indefinitely), what
works best is a pulse-charging technique. Hit 'em with a brief pulse
of current at a high rate (C or C/2 or so) every once in a while, and
let them rest between pulses. Time the pulses so that the total
charge delivered averages out to around 1-2% of their rated capacity
per day. This should keep them topped up (countering their tendency
to self-discharge) without overcharging them.

You should get NiMH cells with at least 2500mAh capacity. They're not
expensive. I also recommend the Maha/Powerex MH-C9000 charger.

For batteries which will be charged up, and then discharged heavily
within a few days to a week, that's good advice. Ditto if you're
planning to keep them hooked to a properly-designed maintenance charger.

For batteries that you're planning to charge, and then leave on the
shelf (or in equipment) for weeks at a time, I think it's better to go
with the new style of "ultra-low self discharge" NiMH cells - Sanyo
Eneloops, or Powerex Immedions, or Hybrios, or types of that sort.
Their rated capacity is lower (2000-2100 mAh), but unlike the older
style of NiMH they'll hold most of their charge for months.

I second the recommendation for the MH-C9000. A very neat piece of kit.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[William Sommerwerck]

"Dave Platt" <dplatt@radagast.org> wrote in message
news:n5imi5-q76.ln1@radagast.org...

A very low (e.g. C/100 or so) charge rate seems to be safe,
I gather, but it's also rather ineffective for NiMH cells -- they
have a poor "charge acceptance" at low charge rates, and
most of the power just turns into heat.

Maha says roughly the same thing. The recommend charging at at least 0.3C,
though it's not clear whether the reason is to push the cell towards a
significant delta-V at full charge, or to charge more "efficiently". I'm
bothered by the temperature rise, and tend to charge at 0.2C, which (based
on many years using nicads), seems downright excessive!

I don't expect any rechargeably battery to hold its charge indefintely. I
have a big pile of them, and charge them as I need them.

I might add that 2500mAh NiMH cells pretty much mark the end of the alkaline
cell, except for "intermittent", low-drain applications, especially where
frequently swapping the cells would be incovenient (eg, remote controls).
Such cells can provide at least the same run-time as a throw-away alkaline.
And, yes, I've checked and confirmed this.

I second the recommendation for the MH-C9000. A very neat piece of kit.

I wish I'd one 20 years ago.

 

[William Sommerwerck]

I seem to observe that *lower* capacity batteries perform *better*
with respect to Ri and lifecycle.

Of course, lifecycle has to be weighed against how often you have to swap
out the cells. If a single high-capacity battery gives you no more than the
same total runtime over its life as multiple lower-capacity batteries,
you're still ahead of the game.

 

[Dave Platt]

In article <n4CdnZHdx5Tsa8XVnZ2dnUVZ_sninZ2d@comcast.com>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

A very low (e.g. C/100 or so) charge rate seems to be safe,
I gather, but it's also rather ineffective for NiMH cells -- they
have a poor "charge acceptance" at low charge rates, and
most of the power just turns into heat.

Maha says roughly the same thing. The recommend charging at at least 0.3C,
though it's not clear whether the reason is to push the cell towards a
significant delta-V at full charge, or to charge more "efficiently".

I think it's the former. The higher charging current leads to a more
rapid flattening-out of the voltage-vs.-time curve, and also leads to
a more rapid rise in temperature at the full-charge point. Both of
these make it easier for a good charger's circuitry to detect the
full-charge point and shut down the current flow at the right time.

I'm
bothered by the temperature rise, and tend to charge at 0.2C, which (based
on many years using nicads), seems downright excessive!

I believe that Powerex actually *increased* their minimum-charge-rate
recommendation for the MH-C9000 - it was originally .2C and now they
recommend .3C or above. This change, plus some firmware changes in
the more recent versions, seems to have eliminated the problem of "the
charger never shuts off, and the batteries get really hot" problem
that early revs of this charger were prone to.

I've been charging my various low-discharge AA cells in a C9000 at .5C
or so (the charger's 1000 mAh default rate) and they don't seem to
much, if any, warmer at charge-shutdown time than if I stick them in
an old-style .1C slow-charger and let 'em fill up. The C9000 appears
to detect the full-charge state quite reliably... I have yet to run
into a single hot-battery problem.

At this point, I prefer to stick with one of two charge regimes - a
fairly fast charge (.5C) using voltage-and-temperature cutoff, or a
slow one (.1C or below) using a timed cutoff.

I might add that 2500mAh NiMH cells pretty much mark the end of the alkaline
cell, except for "intermittent", low-drain applications, especially where
frequently swapping the cells would be incovenient (eg, remote controls).
Such cells can provide at least the same run-time as a throw-away alkaline.
And, yes, I've checked and confirmed this.

I can well believe it.

The major niches I see for alkaline AAs are the ones you suggest (e.g.
remote controls) and long-storage-time emergency backup applications
(e.g. I keep a partial "brick" of AA alkalines with my amateur-radio
"go-kit", so I'd have a couple of days of on-the-air time prior to
having to drag out a recharger).

For my wife's digital cameras (and my own) I've settled on a
combination of low-discharge-rate NiMH for day-to-day use, and lithium
AA disposables for travelling (they're light, really long lasting, and
it saves the trouble of taking an overseas-voltage-qualified charger
along).

I wish I'd one 20 years ago.

Yah. I've been rather dissatisfied for years with commercial NiCd/NiMH
chargers, and toyed with the idea of designing my own with a boatload
of flexibility and control, good full-charge detection, reconditioning
circuitry, etc. - an ideal application for a small microcontroller.
Never got around to doing it... and now there's no need to go to the
effort!

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Dave Platt]

In article <n4CdnZHdx5Tsa8XVnZ2dnUVZ_sninZ2d@comcast.com>,
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

A very low (e.g. C/100 or so) charge rate seems to be safe,
I gather, but it's also rather ineffective for NiMH cells -- they
have a poor "charge acceptance" at low charge rates, and
most of the power just turns into heat.

Maha says roughly the same thing. The recommend charging at at least 0.3C,
though it's not clear whether the reason is to push the cell towards a
significant delta-V at full charge, or to charge more "efficiently".

I think it's the former. The higher charging current leads to a more
rapid flattening-out of the voltage-vs.-time curve, and also leads to
a more rapid rise in temperature at the full-charge point. Both of
these make it easier for a good charger's circuitry to detect the
full-charge point and shut down the current flow at the right time.

I'm
bothered by the temperature rise, and tend to charge at 0.2C, which (based
on many years using nicads), seems downright excessive!

I believe that Powerex actually *increased* their minimum-charge-rate
recommendation for the MH-C9000 - it was originally .2C and now they
recommend .3C or above. This change, plus some firmware changes in
the more recent versions, seems to have eliminated the problem of "the
charger never shuts off, and the batteries get really hot" problem
that early revs of this charger were prone to.

I've been charging my various low-discharge AA cells in a C9000 at .5C
or so (the charger's 1000 mAh default rate) and they don't seem to
much, if any, warmer at charge-shutdown time than if I stick them in
an old-style .1C slow-charger and let 'em fill up. The C9000 appears
to detect the full-charge state quite reliably... I have yet to run
into a single hot-battery problem.

At this point, I prefer to stick with one of two charge regimes - a
fairly fast charge (.5C) using voltage-and-temperature cutoff, or a
slow one (.1C or below) using a timed cutoff.

I might add that 2500mAh NiMH cells pretty much mark the end of the alkaline
cell, except for "intermittent", low-drain applications, especially where
frequently swapping the cells would be incovenient (eg, remote controls).
Such cells can provide at least the same run-time as a throw-away alkaline.
And, yes, I've checked and confirmed this.

I can well believe it.

The major niches I see for alkaline AAs are the ones you suggest (e.g.
remote controls) and long-storage-time emergency backup applications
(e.g. I keep a partial "brick" of AA alkalines with my amateur-radio
"go-kit", so I'd have a couple of days of on-the-air time prior to
having to drag out a recharger).

For my wife's digital cameras (and my own) I've settled on a
combination of low-discharge-rate NiMH for day-to-day use, and lithium
AA disposables for travelling (they're light, really long lasting, and
it saves the trouble of taking an overseas-voltage-qualified charger
along).

I wish I'd one 20 years ago.

Yah. I've been rather dissatisfied for years with commercial NiCd/NiMH
chargers, and toyed with the idea of designing my own with a boatload
of flexibility and control, good full-charge detection, reconditioning
circuitry, etc. - an ideal application for a small microcontroller.
Never got around to doing it... and now there's no need to go to the
effort!

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[William Sommerwerck]

Apologies for jumping in late but before you buy, hop over
to Amazon.com and read the reviews on the MH-C9000.

I was particularly "impressed" with the reviewer who felt that its wealth of
features made it too difficult to use.

The point about watching what you're doing when recharging with such a
powerful unit is well-taken, though. I've had no problems with mine.

 

[gb]

"bz" <bz+ser@ch100-5.chem.lsu.edu> wrote in message
news:Xns9AC080A9DC414WQAHBGMXSZHVspammote@130.39.198.139...

"gb" <w9nogbspam@arrlspamno.net> wrote in news:TMydncjw-
Z_Wc8rVnZ2dnUVZ_qvinZ2d@comcast.com:

MATCH the MASS
of the tip to the MASS of the soldering area.

Thanks for that information. That sounds like a great hint!


--
bz 73 de N5BZ k

Common error for newcomers to Soldering.
Based on sound physical principles of thermal conduction of heat (Fourier's
law)
http://en.wikipedia.org/wiki/Thermal_conductivity

Greg
w9gb

 

[gb]

"bz" <bz+ser@ch100-5.chem.lsu.edu> wrote in message
news:Xns9AC080A9DC414WQAHBGMXSZHVspammote@130.39.198.139...

"gb" <w9nogbspam@arrlspamno.net> wrote in news:TMydncjw-
Z_Wc8rVnZ2dnUVZ_qvinZ2d@comcast.com:

MATCH the MASS
of the tip to the MASS of the soldering area.

Thanks for that information. That sounds like a great hint!


--
bz 73 de N5BZ k

Common error for newcomers to Soldering.
Based on sound physical principles of thermal conduction of heat (Fourier's
law)
http://en.wikipedia.org/wiki/Thermal_conductivity

Greg
w9gb

 

[Tim Williams]

<anglomont@yahoo.com> wrote in message
news:eb5d7c30-1fd2-4dd7-8345-45056982f98f@x41g2000hsb.googlegroups.com...

there should be 2 diodes near the microwave magnetron

Nope, only need one. The magnetron is the other.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

 

[Tim Williams]

<anglomont@yahoo.com> wrote in message
news:eb5d7c30-1fd2-4dd7-8345-45056982f98f@x41g2000hsb.googlegroups.com...

there should be 2 diodes near the microwave magnetron

Nope, only need one. The magnetron is the other.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

 

[Daniel Who Wants to Know]

<phil-news-nospam@ipal.net> wrote in message
news:g1gkdp01hd6@news1.newsguy.com...

In alt.engineering.electrical Daniel Who Wants to Know
danielthechskid@merrychristmasi.com> wrote:

| Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and
has 3
| HV magnetrons along with 3 each of the other necessary items (cap,
diode,
| etc.). It even has a current transformer that tells the control board
via
| current draw when the magnetrons are warmed up so that the timer doesn't
| start counting down until it is actually cooking. It has a standard
NEMA
| 6-20 plug on it now and will pop a bag of popcorn in roughly 75 seconds
| without scorching it. I can tell you it sure beats the hell out of
regular
| microwave ovens for most things. The only thing I still use the regular
one
| for are items that involve liquids as the Amana tends to make them
either
| boil over or boils out all of the water before the food is cooked.

Will it operate on single phase power, like I have in my home?

Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the
cord is a 14-3 AWG with one conductor being ground, yes it is single phase.

 

[Daniel Who Wants to Know]

<phil-news-nospam@ipal.net> wrote in message
news:g1gkdp01hd6@news1.newsguy.com...

In alt.engineering.electrical Daniel Who Wants to Know
danielthechskid@merrychristmasi.com> wrote:

| Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and
has 3
| HV magnetrons along with 3 each of the other necessary items (cap,
diode,
| etc.). It even has a current transformer that tells the control board
via
| current draw when the magnetrons are warmed up so that the timer doesn't
| start counting down until it is actually cooking. It has a standard
NEMA
| 6-20 plug on it now and will pop a bag of popcorn in roughly 75 seconds
| without scorching it. I can tell you it sure beats the hell out of
regular
| microwave ovens for most things. The only thing I still use the regular
one
| for are items that involve liquids as the Amana tends to make them
either
| boil over or boils out all of the water before the food is cooked.

Will it operate on single phase power, like I have in my home?

Considering a NEMA 6-20 plug only has the 2 hot prongs plus ground and the
cord is a 14-3 AWG with one conductor being ground, yes it is single phase.

 

[Daniel Who Wants to Know]

"msg" <msg@_cybertheque.org_> wrote in message
news:KLWdnQNX5KSnL6bVnZ2dnUVZ_orinZ2d@posted.cpinternet...

Daniel Who Wants to Know wrote:

snip

Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and has
3 HV magnetrons along with 3 each of the other necessary items (cap,
diode, etc.).

Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

Each mag has its own waveguide with a rotating antenna at the end that
extends into the oven cavity. 2 of the waveguides are at the top of the
cavity firing down and the third is at the bottom firing up. The HV
transformer primaries are wired so that the top 2 mags fire on the positive
alternation of the AC sine wave and the bottom mag fires on the negative
alternation. The top 2 antennas are driven by a single timer motor with
large plastic gears (complete with timing marks) so that they both are
pointing the same direction at all times as they rotate. The HV
transformers have tapped primaries so that the oven can operate on either
208 or 230 volts with no change in output power. Also there is a small
208-230 volt boost autotransformer that boosts the voltage for the cavity
lamp, cooling blower, and antenna motors when the oven is plugged in to 208.
When the microwave is first plugged in it sits for about 30 seconds to (I
assume) to sense the supplied voltage and frequency so that it uses the
correct taps on the 4 transformers. Oh yeah when the oven is set for less
than 100% power the HV transformers are cycled on and off by 3 triacs (1
each) with arc snubbers across them and there is a relay that cuts the power
to the triac/transformer circuits when the oven is off. Each mag has 2
thermal cutouts, 3 cut off the power to the respective transformer primary
and the other 3 are wired in series and are connected to the logic board
which makes the vacuum fluorescent display show HOT and also causes the oven
to refuse to operate. There is also a thermal fuse in the oven cavity air
discharge duct.

I think I have provided WAY more info than anybody wanted or needed.

 

[Daniel Who Wants to Know]

"msg" <msg@_cybertheque.org_> wrote in message
news:KLWdnQNX5KSnL6bVnZ2dnUVZ_orinZ2d@posted.cpinternet...

Daniel Who Wants to Know wrote:

snip

Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and has
3 HV magnetrons along with 3 each of the other necessary items (cap,
diode, etc.).

Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

Each mag has its own waveguide with a rotating antenna at the end that
extends into the oven cavity. 2 of the waveguides are at the top of the
cavity firing down and the third is at the bottom firing up. The HV
transformer primaries are wired so that the top 2 mags fire on the positive
alternation of the AC sine wave and the bottom mag fires on the negative
alternation. The top 2 antennas are driven by a single timer motor with
large plastic gears (complete with timing marks) so that they both are
pointing the same direction at all times as they rotate. The HV
transformers have tapped primaries so that the oven can operate on either
208 or 230 volts with no change in output power. Also there is a small
208-230 volt boost autotransformer that boosts the voltage for the cavity
lamp, cooling blower, and antenna motors when the oven is plugged in to 208.
When the microwave is first plugged in it sits for about 30 seconds to (I
assume) to sense the supplied voltage and frequency so that it uses the
correct taps on the 4 transformers. Oh yeah when the oven is set for less
than 100% power the HV transformers are cycled on and off by 3 triacs (1
each) with arc snubbers across them and there is a relay that cuts the power
to the triac/transformer circuits when the oven is off. Each mag has 2
thermal cutouts, 3 cut off the power to the respective transformer primary
and the other 3 are wired in series and are connected to the logic board
which makes the vacuum fluorescent display show HOT and also causes the oven
to refuse to operate. There is also a thermal fuse in the oven cavity air
discharge duct.

I think I have provided WAY more info than anybody wanted or needed.

 

[Daniel Who Wants to Know]

"msg" <msg@_cybertheque.org_> wrote in message
news:KLWdnQNX5KSnL6bVnZ2dnUVZ_orinZ2d@posted.cpinternet...

Daniel Who Wants to Know wrote:

snip

Yes like my Amana commercial RadarRange which is 4KW in 2.2KW out and has
3 HV magnetrons along with 3 each of the other necessary items (cap,
diode, etc.).

Does this oven somehow injection-lock the magnetrons? Can you describe
the (RF) plumbing?

Michael

In my other post I forgot to mention that Sam already has most of what I
wrote posted on his site somewhere as I sent him the details awhile back.

 

[Dave Platt]

My sincere thanks for all replies and the aggregated expertise! It
seems that I should get a Maha/Powerex MH-C9000 charger. I'm presently
using a Sanyo "Super Quick Charger", model NC-MQH01U - bought with a
pack of NiMH's at COSTCO a couple of years ago for around $30. I've
no idea what the so-called "C-rate" is but the cells get quite hot
before it cuts off (my guess is that it does not have a temperature
sensors.) Does anyone know a good source, preferably in Canada, for
the Maha/Powerex MH-C9000 charger?

I'd suggest seeing if Thomas Distributing will ship to Canada.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Dave Platt]

My sincere thanks for all replies and the aggregated expertise! It
seems that I should get a Maha/Powerex MH-C9000 charger. I'm presently
using a Sanyo "Super Quick Charger", model NC-MQH01U - bought with a
pack of NiMH's at COSTCO a couple of years ago for around $30. I've
no idea what the so-called "C-rate" is but the cells get quite hot
before it cuts off (my guess is that it does not have a temperature
sensors.) Does anyone know a good source, preferably in Canada, for
the Maha/Powerex MH-C9000 charger?

I'd suggest seeing if Thomas Distributing will ship to Canada.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Geoffrey S. Mendelson]

Franc Zabkar wrote:

The subject VCR is powering up with "SAFE" in the display. I suspect
this is due to a child lock.

No, there is a copy of "Marathon Man" stuck in it.



http://www.imdb.com/title/tt0074860/quotes

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Geoffrey S. Mendelson]

Franc Zabkar wrote:

The subject VCR is powering up with "SAFE" in the display. I suspect
this is due to a child lock.

No, there is a copy of "Marathon Man" stuck in it.



http://www.imdb.com/title/tt0074860/quotes

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM