sci.electronics.repair@googlegroups.com

Today's topics:

* Reduce power of a microwave oven? - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/76e6c7ef368fc8a0?hl=en
* Pet hates ? - 5 messages, 4 authors
http://groups.google.com/group/sci.electronics.repair/t/e7925b5c2233e9ec?hl=en
* Polaroid Pola-Pack battery chemistry - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/84793df5d234c33c?hl=en
* Brittle plastic? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/2baa17ceeaefe60f?hl=en
* Awesome speakers!! - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/19ed616a0fe70f02?hl=en
* South Western federal taxation 2011 Individual test bank and solution manual
is available for purchase at affordable prices. Contact me at estudyguides[at]
gmail.com to buy it today. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/1b41a3cf8e65c3ae?hl=en
* ESR meters repository - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/ef29050e57f5e655?hl=en

==============================================================================
TOPIC: Reduce power of a microwave oven?
http://groups.google.com/group/sci.electronics.repair/t/76e6c7ef368fc8a0?hl=en
==============================================================================

== 1 of 3 ==
Date: Wed, Jan 19 2011 6:01 pm
From: "Arfa Daily"

"mike" <spamme9@gmail.com> wrote in message
news:ih7ie4$nb5$1@news.eternal-september.org...
> PeterD wrote:
>> On Tue, 18 Jan 2011 20:35:49 -0500, "Michael A. Terrell"
>> <mike.terrell@earthlink.net> wrote:
>>
>>> mike wrote:
>>>> My 27 year old microwave oven was down below 400W output and taking a
>>>> long
>>>> time to heat my coffee.
>>>> So, I went out and bought a 1100W one.
>>>> Big mistake.
>>>> It works fine on coffee, but WAY overcooks small stuff.
>>>> Yes, it has a power level setting, but the on-time is 15 seconds
>>>> and they modulate the off-time.
>>>> I tried to heat a frozen hamburger patty. It boils the liquid around
>>>> the outside for 15 seconds, but the inside is still frozen.
>>>> This really messes up the cheese stuck to it. If I leave it in
>>>> the frozen burger, it comes out awful.
>>>>
>>>> What are my options for reducing power?
>>>> Yes, I can stick in a pot of water to absorb energy, but I'm
>>>> looking for a more elegant solution.
>>>> I assume there's nothing I can do on the primary side, cause of the
>>>> filament voltage requirements.
>>>> Assuming I can find a switch that can take the voltage and current,
>>>> can I switch the value of the big cap? Not much else in there to play
>>>> with.
>>>>
>>>> Alternatively, there's stuff they put in the bottom of microwave
>>>> popcorn
>>>> that heats up from microwaves. What is that stuff? Maybe I can find a
>>>> pan with that in the bottom to average out the energy over time.
>>>> There's a "as seen on TV" serving plate that you heat in the microwave.
>>>> It's made of granite. What is it in the granite that gets heated?
>>>> IF I could find a square of floor tile in ceramic or granite, ceramic
>>>> is
>>>> more easily available, I could stick one of them in the bottom of the
>>>> oven.
>>>>
>>>> Suggestions?
>>>
>>> RTFM to see how to set the cook power.
>>
>> Or use the defrost cycle!
>
> When I ask a question on line, I go to great lengths to describe the issue
> in detail to keep the discussion from running off in all directions.
> It rarely works, but I keep hoping that people will actually read the
> info before shooting from the hip.
>
> With this, and every other low-end non-inverter microwave oven I've ever
> encountered, the power is adjusted by pulsing the magnetron in bursts
> of approximately 15 seconds followed by an off-time required to get the
> average power you programmed.
> The RELEVANT number is the 15 second MINIMUM on-time. Doesn't matter
> what buttons you push, you can't get an on-time less than 15 seconds
> unless
> you program a single burst that's shorter.
> If 15 seconds is long enough to boil the liquid in part of the payload,
> defrosting can make a mess of things.
>
> In this case, the "defrost" button has some algorithm that they don't
> disclose
> and I've been too lazy to reverse-engineer, but the minimum on-time
> is still about 15 seconds.
> It's a fundamental property of the design.

All correct by my experience, also

Arfa

== 2 of 3 ==
Date: Wed, Jan 19 2011 9:49 pm
From: "larry moe 'n curly"

mike wrote:
> larry moe 'n curly wrote:
> >
> > mike wrote:
> >
> >> My 27 year old microwave oven was down below 400W output and taking a long
> >> time to heat my coffee.
> >> So, I went out and bought a 1100W one.
> >> Big mistake.
> >> It works fine on coffee, but WAY overcooks small stuff.
> >> Yes, it has a power level setting, but the on-time is 15 seconds
> >> and they modulate the off-time.
> >
> >> Suggestions?
> >
> > Put in a smaller high voltage capacitor?
> Thanks for repeating one of my suggested options.
> Can you be a little more theoretical?
> One reference suggested that the cap is actually
> sized to resonate with the transformer. That would make
> the change of cap value much more sensitive than just a power
> ratio.
> Relevant input?
> Thanks, mike

I thought you meant adding another capacitor and switching between it
and the original.

I doubt the capacitor resonates because years ago someone mentioned a
line of microwaves being identical except for power rating, cavity
size, and the size of the high voltage capacitor, which ranged from
about 0.6uF to 1.0uF.

> > Get an oven with inverter power control, like a Panasonic?
> Simple matter of price ;-)

They're not as expensive as some people implied.

== 3 of 3 ==
Date: Thurs, Jan 20 2011 2:23 am
From: mike

larry moe 'n curly wrote:
>
> mike wrote:
>> larry moe 'n curly wrote:
>>> mike wrote:
>>>
>>>> My 27 year old microwave oven was down below 400W output and taking a long
>>>> time to heat my coffee.
>>>> So, I went out and bought a 1100W one.
>>>> Big mistake.
>>>> It works fine on coffee, but WAY overcooks small stuff.
>>>> Yes, it has a power level setting, but the on-time is 15 seconds
>>>> and they modulate the off-time.
>>>> Suggestions?
>>> Put in a smaller high voltage capacitor?
>> Thanks for repeating one of my suggested options.
>> Can you be a little more theoretical?
>> One reference suggested that the cap is actually
>> sized to resonate with the transformer. That would make
>> the change of cap value much more sensitive than just a power
>> ratio.
>> Relevant input?
>> Thanks, mike
>
> I thought you meant adding another capacitor and switching between it
> and the original.

Yes, that's what I had in mind. All you need is a switch that can
handle that much volts safely...and maybe some means to make sure
that switching a charged cap doesn't explode the diode or the switch.

Some months ago, I had to replace the diode in my old one.
Hooked a resistor to a couple of clip leads and hooked them to the cap.
I never did find any of the resistor pieces. May have gotten swept up
when I cleaned up the puddle I made. ;-)
>
> I doubt the capacitor resonates because years ago someone mentioned a
> line of microwaves being identical except for power rating, cavity
> size, and the size of the high voltage capacitor, which ranged from
> about 0.6uF to 1.0uF.

>
>>> Get an oven with inverter power control, like a Panasonic?
>> Simple matter of price ;-)
>
> They're not as expensive as some people implied.
It's all relative. Paid $80 for mine. I did visit a few stores and the
inverter ones seemed to be almost 3x that and they don't go on sale
often. Knowing what I know now, I might have gone with the inverter.
Spilt milk now...

==============================================================================
TOPIC: Pet hates ?
http://groups.google.com/group/sci.electronics.repair/t/e7925b5c2233e9ec?hl=en
==============================================================================

== 1 of 5 ==
Date: Wed, Jan 19 2011 8:26 pm
From: "Michael Kennedy"

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:kzMZo.214$%p6.39@newsfe03.ams2...
>
>
> "William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
> news:ih7bqe$ajf$1@news.eternal-september.org...
>>> I once got in a lot of trouble with my boss when I was young and worked
>> for
>>> a U.S. based company. At that time, I didn't understand that there was a
>> big
>>> difference between British 'tongue-in-cheek' humour, and the much more
>>> direct U.S. type. I was talking on the phone to one of the designers of
>>> a
>>> piece of equipment that we sold here in the UK, and asked the guy if he
>>> could arrange to send me some screws for the cabinet, as they were a
>> thread
>>> that we didn't readily get over here. He asked if I knew exactly what
>>> size
>>> they were so I replied, quick as a flash, thinking that I was being
>>> funny,
>>> "I guess that they are round about 3/16ths APF." "What's APF ?" the guy
>>> asked. "American Piss Fit", said I ...
>>
>>> Stony silence on the phone. Half an hour later, I was summoned to the
>> boss's
>>> office. Apparently, the guy had been really offended by this, thinking
>> that
>>> it was a slur on what he considered to be good American engineering, and
>> had
>>> called my boss to complain about me. Just goes to show how easily
>>> offence
>>> can be caused between nations, even when they speak what's basically the
>>> same language ... :-)
>>
>> It's hard /not/ to interpret such a description as an intentional insult.
>> I
>> can't imagine what it actually means -- in any innocuous sense, anyway.
>>
>>
>
> There ya go then ! Anyone from the UK would see it as a quick-fire
> throw-away line, and would laugh at it. It's sort of intended to be
> 'barbed', but not in a malicious way. It's a very hard to describe form of
> humour that is quite prevalent over here.
>
> Arfa

We have that kind of humor in the US too.. But only amongst friends or
people you know fairly well. If a stranger uses sharp humor with me (some
do) and It gives the feeling of you dont know me well enough to be poking
humor at me, and we also usually take the fact there is ususaly truth in
humor.. And honestly you probaly think the US standards are idioic and
stupid to still be using when the rest of the world is using the metric
system. Thats the feeling I get here in Japan at least. People cant
understand why the US uses the old system still.

Anyhow.. Just my $0.02

== 2 of 5 ==
Date: Wed, Jan 19 2011 9:41 pm
From: "Michael Kennedy"

"Lab1" <.@...> wrote in message
news:ih7h4o$uc9$1@news.eternal-september.org...
> On 1/19/2011 2:25 PM, Meat Plow wrote:
>
>>> Great dollops of that white goo between metal to metal thermally
>>> conductive surfaces.
>
>> Overuse of that stuff is worse for thermal conductivity than none at all.
>> I've clean up gobs of it since they started using it decades ago.
>
> This is something I'm currently wondering about. I have a fridge-like
> thermo-electric cooler than has two sections, top and bottom, with
> different temperatures. The top suddenly stopped getting cool at all, so I
> took it apart to figure out why. The fans and voltages were all there so I
> broke down the heat sinks on the bad one to get to the Peltier device.
> With it isolated, I powered it up briefly and much to my surprise the
> Peltier device got hot real quickly with the opposite side getting cooler.
> So the device works, it has to be something with the heat sinks?
> They did use white goop on both sides, but very little and it was already
> dried. The heat sinks are milled flat where they make contact with the
> Peltier device, so my thinking is they need new goop.
> Looking around I found that Star heat sink compound is about the best you
> can get, so I ordered some. It just arrived the other day so I'm planning
> to clean up the old goop, put on some new goop and hope for the best. I
> don't think too much would be an issue in this case, I want it as cold as
> possible.
>
>
>
>
>
> --
> -Scott

Too much of the stuff will be a problem whether you are trying to heat or
cool. I have some major doubts that a thin coating of that stuff would be
enough to make any major difference in the performance of peteler junction.
Now on the other hand, if the heatsink is loose... That could give you some
real issues.

== 3 of 5 ==
Date: Wed, Jan 19 2011 11:03 pm
From: dplatt@radagast.org (Dave Platt)

In article <Q_adnVJtm5SAVqrQnZ2dnVY3go-dnZ2d@giganews.com>,
Michael Kennedy <mike@com> wrote:

>> They did use white goop on both sides, but very little and it was already
>> dried. The heat sinks are milled flat where they make contact with the
>> Peltier device, so my thinking is they need new goop.

>Too much of the stuff will be a problem whether you are trying to heat or
>cool. I have some major doubts that a thin coating of that stuff would be
>enough to make any major difference in the performance of peteler junction.
>Now on the other hand, if the heatsink is loose... That could give you some
>real issues.

Michael is quite correct.

The thing about heatsink compound, is that you should only use a
*very* thin layer, and use it between surfaces which are already flat
and well-fitting. Adding a thicker layer of heatsink compound than is
necessary, will actually reduce thermal conductivity.

You want as much direct metal-to-metal or metal-to-ceramic contact as
you can get - enthusiasts who "overclock" their PCs will often flatten
and polish the top of the CPU and the bottom of the heatsink to
increase direct contact. A *thin* smear of heatsink compound is
appropriate... just enough to fill the remaining gaps between the
heatsink and the heat-sunk :-). You almost want to smear it on, and
then wipe most of it off gently with a single-edged razor blade, so
that there is no excess buildup between the two surfaces.

And, yes, if the heatsink actually comes loose from the Peltier
junction (e.g. if it was originally spring-clipped in place, and the
clips are loose or have fatigued and lost pressure) then you've got
problems... you'll get a layer of air between the two surfaces, and
thermal conductivity will become quite poor. Adding a thicker layer
of goop to try to fill the gap isn't the right thing to do - instead,
fix whatever caused the devices to become loose, clean the surfaces,
reapply a *thin* layer of compound, and secure the devices back
together with the proper amount of pressure.

If there was (apparently) nothing holding the two surfaces together -
no clips or retainers - then you're probably dealing with a "thermally
conductive adhesive". Some of these are good, some are poor... and
you'll have to strip off all of the remains, and then reapply (again)
a very thin layer of a suitable thermal adhesive, and fasten the parts
back together with appropriate pressure until the adhesive cures.

--
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!

== 4 of 5 ==
Date: Thurs, Jan 20 2011 12:09 am
From: "N_Cook"

Michael Kennedy <mike@com> wrote in message
news:KPGdndudDvPFJKrQnZ2dnVY3goudnZ2d@giganews.com...
>
> "Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
> news:kzMZo.214$%p6.39@newsfe03.ams2...
> >
> >
> > "William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
> > news:ih7bqe$ajf$1@news.eternal-september.org...
> >>> I once got in a lot of trouble with my boss when I was young and
worked
> >> for
> >>> a U.S. based company. At that time, I didn't understand that there was
a
> >> big
> >>> difference between British 'tongue-in-cheek' humour, and the much more
> >>> direct U.S. type. I was talking on the phone to one of the designers
of
> >>> a
> >>> piece of equipment that we sold here in the UK, and asked the guy if
he
> >>> could arrange to send me some screws for the cabinet, as they were a
> >> thread
> >>> that we didn't readily get over here. He asked if I knew exactly what
> >>> size
> >>> they were so I replied, quick as a flash, thinking that I was being
> >>> funny,
> >>> "I guess that they are round about 3/16ths APF." "What's APF ?" the
guy
> >>> asked. "American Piss Fit", said I ...
> >>
> >>> Stony silence on the phone. Half an hour later, I was summoned to the
> >> boss's
> >>> office. Apparently, the guy had been really offended by this, thinking
> >> that
> >>> it was a slur on what he considered to be good American engineering,
and
> >> had
> >>> called my boss to complain about me. Just goes to show how easily
> >>> offence
> >>> can be caused between nations, even when they speak what's basically
the
> >>> same language ... :-)
> >>
> >> It's hard /not/ to interpret such a description as an intentional
insult.
> >> I
> >> can't imagine what it actually means -- in any innocuous sense, anyway.
> >>
> >>
> >
> > There ya go then ! Anyone from the UK would see it as a quick-fire
> > throw-away line, and would laugh at it. It's sort of intended to be
> > 'barbed', but not in a malicious way. It's a very hard to describe form
of
> > humour that is quite prevalent over here.
> >
> > Arfa
>
>
> We have that kind of humor in the US too.. But only amongst friends or
> people you know fairly well. If a stranger uses sharp humor with me (some
> do) and It gives the feeling of you dont know me well enough to be poking
> humor at me, and we also usually take the fact there is ususaly truth in
> humor.. And honestly you probaly think the US standards are idioic and
> stupid to still be using when the rest of the world is using the metric
> system. Thats the feeling I get here in Japan at least. People cant
> understand why the US uses the old system still.
>
> Anyhow.. Just my $0.02
>

I got the impression that was where Ricky Gervaise went wrong, last week, at
the latest Hollywood bash

== 5 of 5 ==
Date: Thurs, Jan 20 2011 3:29 am
From: "Mark Zacharias"

Packing peanuts.

Probe slips.

People begging me to work on stuff which I used to turn away, but now have
to take in because business is slow.

Mark Z.

==============================================================================
TOPIC: Polaroid Pola-Pack battery chemistry
http://groups.google.com/group/sci.electronics.repair/t/84793df5d234c33c?hl=en
==============================================================================

== 1 of 3 ==
Date: Wed, Jan 19 2011 8:37 pm
From: "hrhofmann@att.net"

Going thru my pile of old batteries, I discovered 3 1995 Polaroid pola-
pack batteries. They still read above 7.2 V. I think they were 7.5V
when new. Whatever chemistry they used has held up for 16 years. I
am wondering what the chemistry of these batteries is that they
haven't self-discharged after this long period of time. Does anyone
know for sure what Polaroid used?

== 2 of 3 ==
Date: Wed, Jan 19 2011 11:39 pm
From: Jeff Liebermann

On Wed, 19 Jan 2011 20:37:04 -0800 (PST), "hrhofmann@att.net"
<hrhofmann@att.net> wrote:

>Going thru my pile of old batteries, I discovered 3 1995 Polaroid pola-
>pack batteries. They still read above 7.2 V. I think they were 7.5V
>when new. Whatever chemistry they used has held up for 16 years. I
>am wondering what the chemistry of these batteries is that they
>haven't self-discharged after this long period of time. Does anyone
>know for sure what Polaroid used?

Google for "Polaroid Polapulse Battery" and you'll find plenty of
photos and references.
The P80 and P100 are 6V at 250ma-hr and Zinc-Manganese dioxide.
The P500 are 6V at 1400ma-hr and Lithium-Manganese dioxide.
Note that they can be recharged successfully a few times.

<http://users.rcn.com/fcohen/Polaroid.htm>

Still available for sale:
<http://users.rcn.com/fcohen/>

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

== 3 of 3 ==
Date: Thurs, Jan 20 2011 1:36 am
From: "N_Cook"

<hrhofmann@att.net> wrote in message
news:dacc68a5-d1f6-480b-938a-43abe32a7d3b@z5g2000yqb.googlegroups.com...
> Going thru my pile of old batteries, I discovered 3 1995 Polaroid pola-
> pack batteries. They still read above 7.2 V. I think they were 7.5V
> when new. Whatever chemistry they used has held up for 16 years. I
> am wondering what the chemistry of these batteries is that they
> haven't self-discharged after this long period of time. Does anyone
> know for sure what Polaroid used?

what do they read with say 1Kohm over them ?

==============================================================================
TOPIC: Brittle plastic?
http://groups.google.com/group/sci.electronics.repair/t/2baa17ceeaefe60f?hl=en
==============================================================================

== 1 of 1 ==
Date: Wed, Jan 19 2011 11:15 pm
From: "larry moe 'n curly"

I got rid of my vintage 1995 Sanyo TV because the plastic case was so
brittle it didn't seem capable of safely supporting the weight of the
CRT, but the plastic of my 1976 TV seems fine. Both cases were made
of fire retardant ABS, but why was it so much more brittle in the
newer TV?

==============================================================================
TOPIC: Awesome speakers!!
http://groups.google.com/group/sci.electronics.repair/t/19ed616a0fe70f02?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jan 20 2011 1:49 am
From: "N_Cook"

Lab1 <.@...> wrote in message
news:ih80l7$ni4$1@news.eternal-september.org...
> On 1/19/2011 7:28 PM, Archon wrote:
> > I was thinking of buying these, can anyone suggest some suitable gold
> > infused 200 Amp speaker wire with low oxygen content?
>
> 3/0 copper is the only wire you will find that can handle 200 amps, and
> it's about 1/2 inch in diameter.
>
> I think you mean 200 watts.
>
> --
> -Scott
>

No you need full 200 amp capacity wiring for the peak demands for the odd
picosecond during use, for the best transcription

==============================================================================
TOPIC: South Western federal taxation 2011 Individual test bank and solution
manual is available for purchase at affordable prices. Contact me at
estudyguides[at]gmail.com to buy it today.
http://groups.google.com/group/sci.electronics.repair/t/1b41a3cf8e65c3ae?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jan 20 2011 3:11 am
From: Esolutions

South Western federal taxation 2011 Individual test bank and solution
manual is available for purchase at affordable prices. Contact me at
estudyguides[at]gmail.com to buy it today.

==============================================================================
TOPIC: ESR meters repository
http://groups.google.com/group/sci.electronics.repair/t/ef29050e57f5e655?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jan 20 2011 3:27 am
From: "Arfa Daily"

"Kripton" wrote in message news:4d375cfd$0$29143$426a34cc@news.free.fr...
> hi
>
> for those who want to know more about it I ran a web site about the esr
> meters
> comments welcomed
>
> http://kripton2035.free.fr/esr-repository.html
>
> regards,
>
> --
> ---
> Kripton
>

When the 'Blue' version of Bob's meter first came out, I wrote an article
for a UK magazine, on building the kit. The mag has long ago ceased to be
published. I think I still have the article archived on this machine
somewhere. If it would be of any interest for your site, mail me direct
off-group with a valid address that I can send it to, and you're welcome to
make use of it.

Arfa

==============================================================================

You received this message because you are subscribed to the Google Groups "sci.electronics.repair"
group.

To post to this group, visit http://groups.google.com/group/sci.electronics.repair?hl=en

To unsubscribe from this group, send email to sci.electronics.repair+unsubscribe@googlegroups.com

To change the way you get mail from this group, visit:
http://groups.google.com/group/sci.electronics.repair/subscribe?hl=en

To report abuse, send email explaining the problem to abuse@googlegroups.com

==============================================================================
Google Groups: http://groups.google.com/?hl=en