sci.electronics.repair@googlegroups.com

Today's topics:

* Magnifying glass for smd components - 3 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/152fab9f5593225c?hl=en
* Samsung Monitor - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/b8e64ece9d65ce8d?hl=en
* Electronic curiosities - 7 messages, 6 authors
http://groups.google.com/group/sci.electronics.repair/t/92fb1a53d8547e80?hl=en
* AA-sized conductor (fake battery) wanted - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/33083a4b1e46ccc0?hl=en

==============================================================================
TOPIC: Magnifying glass for smd components
http://groups.google.com/group/sci.electronics.repair/t/152fab9f5593225c?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Jan 15 2011 9:58 pm
From: Baron

Jeff Liebermann Inscribed thus:

> On Sat, 15 Jan 2011 21:23:48 +0000, Baron
> <baron.nospam@linuxmaniac.nospam.net> wrote:
>
>>Yes colours have definitely become harder to read. I've used the
>>"PTFE" tape trick on IC's and SMD parts a number of times to read the
>>markings.
>
> I often use my pocket LED flashing to provide extra illumination. It
> has a built in holder, also known as my teeth.
>
> So, what's the PTFE trick for reading IC and SMD markings? I couldn't
> find anything with Google.
>
Place a short length of plumbers ptfe tape over the surface and rub with
your fingernail.

--
Best Regards:
Baron.

== 2 of 3 ==
Date: Sat, Jan 15 2011 9:59 pm
From: Baron

N_Cook Inscribed thus:

> Baron <baron.nospam@linuxmaniac.nospam.net> wrote in message
> news:igt358$gkj$2@news.eternal-september.org...
>> D Yuniskis Inscribed thus:
>>
>> > On 1/15/2011 10:52 AM, Baron wrote:
>> >> D Yuniskis Inscribed thus:
>> >>> I have found that adequate *light* is more important than
>> >>> magnification (but that may just be the age of my eyes)
>> >>
>> >> I can certainly empathise with that last paragraph. Good lighting
>> >> is very important. Particularly where identifying colors is
>> >> required.
>> >
>> > I find that I need more than "good" :-/
>> >
>> > I used to be able to read the markings on DIPs at arm's length
>> > "with a glance". Now, I need to rock them back and forth to get
>> > the light to reflect off them at the right angle before things
>> > are visible (at times, I swear they have changed to BLACK INK!! :<
>> > )
>> >
>> > Ditto for color codes. Seems like the colors have crept closer
>> > together in the spectrum :-/
>>
>> Yes colours have definitely become harder to read. I've used the
>> "PTFE" tape trick on IC's and SMD parts a number of times to read the
>> markings.
>>
>> --
>> Best Regards:
>> Baron.
>
>
> Shame I didn't patent that PTFE tip

It was probably you I pinched it from. :-)

--
Best Regards:
Baron.

== 3 of 3 ==
Date: Sun, Jan 16 2011 12:25 am
From: "N_Cook"

Jeff Liebermann <jeffl@cruzio.com> wrote in message
news:bnq4j61p5492udfbgq3t441f9eflnrckpa@4ax.com...
> On Sat, 15 Jan 2011 21:23:48 +0000, Baron
> <baron.nospam@linuxmaniac.nospam.net> wrote:
>
> >Yes colours have definitely become harder to read. I've used the "PTFE"
> >tape trick on IC's and SMD parts a number of times to read the
> >markings.
>
> I often use my pocket LED flashing to provide extra illumination. It
> has a built in holder, also known as my teeth.
>
> So, what's the PTFE trick for reading IC and SMD markings? I couldn't
> find anything with Google.
>
> --
> Jeff Liebermann jeffl@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

In the archives of here as
TIP: How to read unreadable IC/transistor lettering
17 Dec 2007

How to read unreadable IC/transistor lettering
Yes, just like magic.
I could not read 3 of the 5 characters on a heat damaged TOP66 power
transistor.
I wondered if a sort of "brass rubbing" would work.
I just happened to have some plumber's PTFE tape to hand ( nominal 0.05 to
0.08 mm thick).
Laid a piece over the power tranny, rubbed with a finger nail, and the
missing characters
came up like magic.
As the characters remained on the PTFE, as an image , I realised you could
use this technique to read IC lettering where it is impossible to read,
because of constrictions and inability to introduce an inspection mirror or
even just
where you cannot get the illumination at just the right angle to read.
You need access space enough to introduce a piece of PTFE and then rub it
with the wooden end of a small artist's brush, or similar, wrapped in some
of the PTFE, so it rubs easily without dragging.
Don't rub too firmly because you want the relief print to show as clear and
the rest of the PTFE becoming translucent rather than the original white.
Remove and read with a backlight or against something matt black. Maybe a
couple of attempts to get a clear image in all parts of the label.
May even be worth trying on reverse-engineering-proofed, rubbed off, IC
lettering. Useful for indistinct moulding logos /
lettering etc on small plastic parts, gives some contrast.
Confirmed - this time a SIL IC with
the lettering side of the IC 2 mm from a large block cap. Would have
required 3 hours taking boards apart and back together to desolder just
to read.
Used a 1mm steel rod covered with some PTFE tape for the "rubbing" and
pulling
a length of PTFE tight around the IC through the gap,
and held tight while rubbing. I urge everyone to give it
a try, so it is impressed on memory for when required in earnest,
its just like magic

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://diverse.4mg.com/index.htm

==============================================================================
TOPIC: Samsung Monitor
http://groups.google.com/group/sci.electronics.repair/t/b8e64ece9d65ce8d?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Jan 15 2011 10:05 pm
From: Baron

William Brown Inscribed thus:

>
>
> I have a LS19MEDSBQ/XSA
>
> How do you remove the back..
>
> Thanks

If its like most LCD screens then you remove the front bezel. Just be
careful you don't crack the screen. Take the stand off first, then you
can lay it down flat.

--
Best Regards:
Baron.

==============================================================================
TOPIC: Electronic curiosities
http://groups.google.com/group/sci.electronics.repair/t/92fb1a53d8547e80?hl=en
==============================================================================

== 1 of 7 ==
Date: Sat, Jan 15 2011 10:08 pm
From: Randy Day

In article
<4d326a24$0$2374$822641b3@news.adtechcomputers.com>,
nobody@but.us.chickens says...
> Trying to teach myself electronics, I've been reading a few textbooks I
> inherited on the subject. Tough going, as my math is in serious need of
> repair.
>
> Anyhow, found a couple of interesting things in these older books:
>
> 1. TRF:
>
> In the section on modulation, demodulation and other radio-related stuff
> one book brings up "the tuned radio-frequency receiver" before
> discussing superhet, as one would expect. But they say;
>
> During the evolution of radio, the tuned-radio-frequency (TRF)
> receiver was used to receive AM signals. Today, a few special
> applications still use TRF receivers.
>
> Now, they go on to explain why TRF is inferior to superheterodyne. But
> I'm curious: are there still any radios that use TRF? and why? (Keep in
> mind this book was written in 1979).
>
> 2. Thermionic converters & magneto-hydrodynamic generators:
>
> Another book (which I frankly don't like as much since it's so
> math-heavy: wouldn't electronics be so easy to learn if all that goddamn
> math didn't get in the way?) covers these somewhat fantastic devices in
> its chapter on "Energy Conversion Phenomena". The thermionic converter
> is especially intriguing, as it seems a fairly efficient (20%) direct
> conversion from heat to electricity. I seem to remember seeing a program
> on PBS about something like magnetohydrodynamics being developed for
> deep-space exploration propulsion.
>
> Are either of these devices being seriously researched or used nowadays?
> Keep in mind that *this* book was written in 1966.

Did you mean deep-ocean exploration? IIRC, the
Russian sub in Hunt for Red October used a
MHD stealth drive.

Couldn't say if anyone's actually using it for
real...

== 2 of 7 ==
Date: Sat, Jan 15 2011 10:14 pm
From: Jeff Liebermann

On Sat, 15 Jan 2011 19:47:23 -0800, David Nebenzahl
<nobody@but.us.chickens> wrote:

Talk about off topic... sigh.

>1. TRF:
>
>In the section on modulation, demodulation and other radio-related stuff
>one book brings up "the tuned radio-frequency receiver" before
>discussing superhet, as one would expect. But they say;
>
> During the evolution of radio, the tuned-radio-frequency (TRF)
> receiver was used to receive AM signals. Today, a few special
> applications still use TRF receivers.
>
>Now, they go on to explain why TRF is inferior to superheterodyne. But
>I'm curious: are there still any radios that use TRF? and why? (Keep in
>mind this book was written in 1979).

Yes, but it's not obvious or really TRF. The reason superheterodyne
receivers were invented was that decent narrow band LC or crystal IF
bandpass filters were not tuneable and didn't work well at higher RF
frequencies. About 45MHz was as high as they went before going exotic
with SAW devices.

These daze, dramatically improved semiconductor technology has
produced chips that work at almost any useful RF frequency. No more
need to downconvert when the IF filtering is done by a DSP (digital
signal processor). Instead of TRF, it's now called "direct
conversion". There's no local oscillator, no mixer, for fixed IF
filter, and probably no LC devices anywhere. Just a ceramic bandpass
filter (or duplexer) some gain, an A/D converter, and a DSP for
demodulation. Most GPS, Wi-Fi, and cellular chipsets work this way.
<http://en.wikipedia.org/wiki/Direct-conversion_receiver>

There are some rather simple TRF devices still around. A freqency
selective voltmeter is sometimes a TRF device. So are some field
strength measurement instruments, and remotes (car alarm, TV remote,
etc).

>2. Thermionic converters & magneto-hydrodynamic generators:
>
>Another book (which I frankly don't like as much since it's so
>math-heavy: wouldn't electronics be so easy to learn if all that goddamn
>math didn't get in the way?) covers these somewhat fantastic devices in
>its chapter on "Energy Conversion Phenomena". The thermionic converter
>is especially intriguing, as it seems a fairly efficient (20%) direct
>conversion from heat to electricity. I seem to remember seeing a program
>on PBS about something like magnetohydrodynamics being developed for
>deep-space exploration propulsion.
>
>Are either of these devices being seriously researched or used nowadays?
>Keep in mind that *this* book was written in 1966.

Yep. Just about anything that has to do with plasma research involves
MHD. However, the generator part is effectively dead because of lousy
efficiency. I think the best it can do is about 20% thermal
efficiency. Light reading:
<http://en.wikipedia.org/wiki/MHD_generator>
The only hope for commercial use of MHD technology is generating
electricity (and some cooling) from waste heat, such as nuclear
reactor coolant.

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

== 3 of 7 ==
Date: Sat, Jan 15 2011 10:29 pm
From: "Phil Allison"

"Jeff Liebermann"

>
> Yes, but it's not obvious or really TRF. The reason superheterodyne
> receivers were invented was that decent narrow band LC or crystal IF
> bandpass filters were not tuneable and didn't work well at higher RF
> frequencies.

** Total hogwash.

That has got nothing to do with the invention and wide adoption of superhet
radios.

> These daze, dramatically improved semiconductor technology has
> produced chips that work at almost any useful RF frequency. No more
> need to downconvert when the IF filtering is done by a DSP (digital
> signal processor). Instead of TRF, it's now called "direct
> conversion".

** TRF and "direct conversion" are separate techniques.

> There's no local oscillator, no mixer, for fixed IF
> filter, and probably no LC devices anywhere. Just a ceramic bandpass
> filter (or duplexer) some gain, an A/D converter, and a DSP for
> demodulation. Most GPS, Wi-Fi, and cellular chipsets work this way.
>
>
> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>

** How hysterically funny.

The bullshitting fool has posted a Wiki link that completely contradicts his
fabricated thesis.

" In telecommunication, a direct-conversion receiver (DCR), also known as
homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design that
demodulates the incoming signal by mixing it with a local oscillator signal
synchronized in frequency to the carrier of the wanted signal. "

..... Phil

== 4 of 7 ==
Date: Sun, Jan 16 2011 12:15 am
From: "N_Cook"

David Nebenzahl <nobody@but.us.chickens> wrote in message
news:4d326a24$0$2374$822641b3@news.adtechcomputers.com...
> Trying to teach myself electronics, I've been reading a few textbooks I
> inherited on the subject. Tough going, as my math is in serious need of
> repair.
>
> Anyhow, found a couple of interesting things in these older books:
>
> 1. TRF:
>
> In the section on modulation, demodulation and other radio-related stuff
> one book brings up "the tuned radio-frequency receiver" before
> discussing superhet, as one would expect. But they say;
>
> During the evolution of radio, the tuned-radio-frequency (TRF)
> receiver was used to receive AM signals. Today, a few special
> applications still use TRF receivers.
>
> Now, they go on to explain why TRF is inferior to superheterodyne. But
> I'm curious: are there still any radios that use TRF? and why? (Keep in
> mind this book was written in 1979).
>
> 2. Thermionic converters & magneto-hydrodynamic generators:
>
> Another book (which I frankly don't like as much since it's so
> math-heavy: wouldn't electronics be so easy to learn if all that goddamn
> math didn't get in the way?) covers these somewhat fantastic devices in
> its chapter on "Energy Conversion Phenomena". The thermionic converter
> is especially intriguing, as it seems a fairly efficient (20%) direct
> conversion from heat to electricity. I seem to remember seeing a program
> on PBS about something like magnetohydrodynamics being developed for
> deep-space exploration propulsion.
>
> Are either of these devices being seriously researched or used nowadays?
> Keep in mind that *this* book was written in 1966.
>
>
> --
> Comment on quaint Usenet customs, from Usenet:
>
> To me, the *plonk...* reminds me of the old man at the public hearing
> who stands to make his point, then removes his hearing aid as a sign
> that he is not going to hear any rebuttals.

Infra long-wave timecode receivers , eg Rugby and Darmstat, are usually TRF.

Which reminds me - I used to use Teletext timecode for within 1 second
accuracy but that was analogue processing - gone now with "digital" delays
to TV . So bad , up to about 8 seconds delay , and variable , the digital
Teletext has only the minutes of time shown

== 5 of 7 ==
Date: Sun, Jan 16 2011 12:38 am
From: David Nebenzahl

On 1/15/2011 10:14 PM Jeff Liebermann spake thus:

> On Sat, 15 Jan 2011 19:47:23 -0800, David Nebenzahl
> <nobody@but.us.chickens> wrote:
>
> Talk about off topic... sigh.

Hey, at least it's about *electronics* ...

>> 1. TRF:
>>
>> In the section on modulation, demodulation and other radio-related
>> stuff one book brings up "the tuned radio-frequency receiver"
>> before discussing superhet, as one would expect. But they say;
>>
>> During the evolution of radio, the tuned-radio-frequency (TRF)
>> receiver was used to receive AM signals. Today, a few special
>> applications still use TRF receivers.
>>
>> Now, they go on to explain why TRF is inferior to superheterodyne.
>> But I'm curious: are there still any radios that use TRF? and why?
>> (Keep in mind this book was written in 1979).
>
> Yes, but it's not obvious or really TRF. The reason superheterodyne
> receivers were invented was that decent narrow band LC or crystal IF
> bandpass filters were not tuneable and didn't work well at higher RF
> frequencies. About 45MHz was as high as they went before going exotic
> with SAW devices.
>
> These daze, dramatically improved semiconductor technology has
> produced chips that work at almost any useful RF frequency. No more
> need to downconvert when the IF filtering is done by a DSP (digital
> signal processor). Instead of TRF, it's now called "direct
> conversion". There's no local oscillator, no mixer, for fixed IF
> filter, and probably no LC devices anywhere. Just a ceramic bandpass
> filter (or duplexer) some gain, an A/D converter, and a DSP for
> demodulation. Most GPS, Wi-Fi, and cellular chipsets work this way.
> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>

OK, so this is why I absolutely *hate* Wikipedia. Here's the lead
paragraph in the article:

In telecommunication, a direct-conversion receiver (DCR), also known as
homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design
that demodulates the incoming signal by mixing it with a local
oscillator signal synchronized in frequency to the carrier of the wanted
signal. The wanted modulation signal is obtained immediately by low-pass
filtering the mixer output, without requiring further detection. Thus a
direct-conversion receiver requires only a single stage of detection and
filtering, as opposed to the more common superheterodyne receiver
design, which converts the carrier frequency to an intermediate
frequency first before extracting the modulation, and thus requires two
stages of detection and filtering.

Now, class, how many things are wrong here? (And please correct *me* if
I'm incorrect):

o First of all, superhet receivers have only one stage of detection and
filtering, not two, after the last IF stage, right? (I suppose there may
be some filtering in or around the mixer stage, but I don't think that's
what they're claiming, which I assume is filtering out the carrier.) So
where do they get "two stages of detection and filtering"?

o Is their explanation of how DCR works even correct? I don't understand
the business of mixing the signal with a LO signal: why would you do
that? They're a little vague: does "synchronized in frequency to the
carrier" mean *exactly* the same frequency as the carrier (???), or some
other frequency to produce a sum or difference frequency? (In which
case, we're back to IF, aren't we, so what's "direct conversion" about this?

If I were in front of a firing squad and had to try to describe DCR
without actually knowing what it is, I'd guess(tm)(R) that it's a bunch
of tuned RF stages followed by a detector.

Anyhow, I think I've shown that even if I'm way off base, Wikipedia
articles tend to be extremely badly written, if not outright full of
doubtful information. What else would one expect of the "encyclopedia"
that any PlayStation-playing, junk-food wolfing pimple-faced
junior-high-school student can edit?

--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

== 6 of 7 ==
Date: Sun, Jan 16 2011 12:47 am
From: David Nebenzahl

On 1/16/2011 12:38 AM David Nebenzahl spake thus:

> o Is their explanation of how DCR works even correct? I don't understand
> the business of mixing the signal with a LO signal: why would you do
> that? They're a little vague: does "synchronized in frequency to the
> carrier" mean *exactly* the same frequency as the carrier (???), or some
> other frequency to produce a sum or difference frequency? (In which
> case, we're back to IF, aren't we, so what's "direct conversion" about this?

It occurred to me that maybe they (the Wikipedia article) are referring
to FM, not AM, DCR (it doesn't say)?

--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

== 7 of 7 ==
Date: Sun, Jan 16 2011 12:50 am
From: Sjouke Burry

David Nebenzahl wrote:
> On 1/15/2011 10:14 PM Jeff Liebermann spake thus:
>
>> On Sat, 15 Jan 2011 19:47:23 -0800, David Nebenzahl
>> <nobody@but.us.chickens> wrote:
>>
>> Talk about off topic... sigh.
>
> Hey, at least it's about *electronics* ...
>
>>> 1. TRF:
>>>
>>> In the section on modulation, demodulation and other radio-related
>>> stuff one book brings up "the tuned radio-frequency receiver"
>>> before discussing superhet, as one would expect. But they say;
>>>
>>> During the evolution of radio, the tuned-radio-frequency (TRF)
>>> receiver was used to receive AM signals. Today, a few special
>>> applications still use TRF receivers.
>>>
>>> Now, they go on to explain why TRF is inferior to superheterodyne.
>>> But I'm curious: are there still any radios that use TRF? and why?
>>> (Keep in mind this book was written in 1979).
>> Yes, but it's not obvious or really TRF. The reason superheterodyne
>> receivers were invented was that decent narrow band LC or crystal IF
>> bandpass filters were not tuneable and didn't work well at higher RF
>> frequencies. About 45MHz was as high as they went before going exotic
>> with SAW devices.
>>
>> These daze, dramatically improved semiconductor technology has
>> produced chips that work at almost any useful RF frequency. No more
>> need to downconvert when the IF filtering is done by a DSP (digital
>> signal processor). Instead of TRF, it's now called "direct
>> conversion". There's no local oscillator, no mixer, for fixed IF
>> filter, and probably no LC devices anywhere. Just a ceramic bandpass
>> filter (or duplexer) some gain, an A/D converter, and a DSP for
>> demodulation. Most GPS, Wi-Fi, and cellular chipsets work this way.
>> <http://en.wikipedia.org/wiki/Direct-conversion_receiver>
>
> OK, so this is why I absolutely *hate* Wikipedia. Here's the lead
> paragraph in the article:
>
> In telecommunication, a direct-conversion receiver (DCR), also known as
> homodyne, synchrodyne, or zero-IF receiver, is a radio receiver design
> that demodulates the incoming signal by mixing it with a local
> oscillator signal synchronized in frequency to the carrier of the wanted
> signal. The wanted modulation signal is obtained immediately by low-pass
> filtering the mixer output, without requiring further detection. Thus a
> direct-conversion receiver requires only a single stage of detection and
> filtering, as opposed to the more common superheterodyne receiver
> design, which converts the carrier frequency to an intermediate
> frequency first before extracting the modulation, and thus requires two
> stages of detection and filtering.
>
> Now, class, how many things are wrong here? (And please correct *me* if
> I'm incorrect):
>
> o First of all, superhet receivers have only one stage of detection and
> filtering, not two, after the last IF stage, right? (I suppose there may
> be some filtering in or around the mixer stage, but I don't think that's
> what they're claiming, which I assume is filtering out the carrier.) So
> where do they get "two stages of detection and filtering"?
>
> o Is their explanation of how DCR works even correct? I don't understand
> the business of mixing the signal with a LO signal: why would you do
> that? They're a little vague: does "synchronized in frequency to the
> carrier" mean *exactly* the same frequency as the carrier (???), or some
> other frequency to produce a sum or difference frequency? (In which
> case, we're back to IF, aren't we, so what's "direct conversion" about this?
>
> If I were in front of a firing squad and had to try to describe DCR
> without actually knowing what it is, I'd guess(tm)(R) that it's a bunch
> of tuned RF stages followed by a detector.
>
> Anyhow, I think I've shown that even if I'm way off base, Wikipedia
> articles tend to be extremely badly written, if not outright full of
> doubtful information. What else would one expect of the "encyclopedia"
> that any PlayStation-playing, junk-food wolfing pimple-faced
> junior-high-school student can edit?
>
>
The story above sounds like descibing a Single Sideband
receiver, where you indeed have to mix in a carrier to detect things.

==============================================================================
TOPIC: AA-sized conductor (fake battery) wanted
http://groups.google.com/group/sci.electronics.repair/t/33083a4b1e46ccc0?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Jan 15 2011 10:10 pm
From: Baron

David Nebenzahl Inscribed thus:

> On 1/15/2011 9:28 PM Michael A. Terrell spake thus:
>
>> Baron wrote:
>>>
>>> Very true ! A trick I've used to clean up the end of damaged bolts.
>>
>> How rebolting! ;-)
>
> Aaaaaah, the guy's nuts I say. Cross-threaded between the ears. Tapped
> out, ready to die.
>

Ooo Nasty. ;-)

--
Best Regards:
Baron.

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