Digest for sci.electronics.repair@googlegroups.com - 12 updates in 6 topics

John Doe <always.look@message.header>: Feb 02 07:25PM

ON THE WAY
 
That brand (probably Chinese) is falsifying reviews for its products.
 
http://www.amazon.com/ON-3800mAh-Rechargeable-Protected-Battery/product-
reviews/B00ODO8ANI/ref=cm_cr_pr_top_recent?ie=UTF8&showViewpoints=0
&sortBy=bySubmissionDateDescending
 
They are verified purchasers, but... Notice almost all of them are
either first, middle/initial, and last names. Then click on "other
reviews" and you can clearly see that they are all the same person.
 
"I can see for miles and miles and miles, Oh yeah... la la la"
 
 
 
 
default <default@defaulter.net>: Feb 02 05:28PM -0500

On Mon, 2 Feb 2015 19:25:39 +0000 (UTC), John Doe
>either first, middle/initial, and last names. Then click on "other
>reviews" and you can clearly see that they are all the same person.
 
>"I can see for miles and miles and miles, Oh yeah... la la la"
 
There must be some folks getting paid to write false reviews on
Amazon. If it sounds too good, etc. you just need to check the "other
reviews from this buyer" (in the five star category) and you will
invariable see that they only have one review for that particular
product, or just reviews on all of one seller's product, and usually
all written within the space of a week or less...
 
This is Amazon's fault IMO for making the system easy to game.
 
I depend on the reviews when buying on Amazon, but sometimes vetting
the reviews is so time consuming it is just easier to find a retailer
that depends on trust to stay in business.
John Doe <always.look@message.header>: Feb 03 03:18AM


> There must be some folks getting paid to write false reviews on
> Amazon.
 
The company "ON THE WAYŽ" is recklessly fraudulent. Here's another
example below. All twenty-one reviews are 5-stars and probably
all by the company itself, on Amazon.
 
http://www.amazon.com/ON-Presenter-Pointer-Powerpoint-Presentation/product-reviews/B00NOR9YPS/ref=cm_cr_pr_top_recent?ie=UTF8&showViewpoints=0&sortBy=bySubmissionDateDescending
default <default@defaulter.net>: Feb 03 09:47AM -0500

On Tue, 3 Feb 2015 03:18:07 +0000 (UTC), John Doe
>example below. All twenty-one reviews are 5-stars and probably
>all by the company itself, on Amazon.
 
>http://www.amazon.com/ON-Presenter-Pointer-Powerpoint-Presentation/product-reviews/B00NOR9YPS/ref=cm_cr_pr_top_recent?ie=UTF8&showViewpoints=0&sortBy=bySubmissionDateDescending
 
 
A google search yielded:
 
"Ms. Carole Adamowicz has left 47 product reviews and they are all 5
star. Raving reviews of all 47 products, coincidentally, all sold by
EcoClean Solutions."
 
From Amazon's own forum...
 
NYT article on false reviews
The Best Book Reviews Money Can Buy
http://tinyurl.com/asosf73
 
Forbes
They claim 300 reviews costs $6,000!
http://tinyurl.com/9gzr29o
Rutherford's venture collapsed when Google stopped him advertising his
services and Amazon pulled many, although not all, of his reviews from
their system. But that hasn't put a stop to false reviews.
 
Indeed, many authors will recognize the phenomenon of the malicious
one-star review designed to sabotage their book. Although Amazon
prohibits "spiteful remarks" it is difficult to get such reviews
removed. There's absolutely no doubt that some of these reviews are
coming from other authors who see self-publishing as a zero sum game
in which if they lose out if another author does well. Others may come
from an author's fans who see anyone else's success as a threat to
their idol, or from grifters and trolls who just get off on attacking
strangers in public.
Jeff Liebermann <jeffl@cruzio.com>: Jan 25 10:12PM -0800


>I was on my computer when my Flat Screen Monitor went black. Just
>suddenly black, no prior indication of a problem. It's a HP 1740.
 
It's probably not the CCFL tubes but rather the capacitors in the
inverter section, which is built onto the power supply PCB.
 
Thank you for including the model number. Please double check the
muddle number as it can be a 1740 or an L1740 display. If you're not
sure, tear it open and compare the photos in the following links.
There are also different mutations of the PCB.
 
You can buy a recap (capacitor replacement) kit for about $7.00:
<http://www.ebay.com/itm/330506313562> (L1740)
<http://www.ebay.com/itm/330502333292> (1740)
There are other kits for replacing the semiconductors, which sometimes
also blow up. If you don't feel like doing the repair, you can also
get PCB's rather cheaply:
<http://www.ebay.com/sch/i.html?_nkw=hp+1740+board>
Again, notice the different PCB mutations.
 
You will probably find the PCB between the two big xformers to be
overheated and scorched. If the PCB crumbles, take some epoxy and
rebuild the burnt area. Use your imagination for how to rework the
PCB traces. With a single sided board, this should be easy.
 
Hint: Take some digital photos as you go along so that you can put it
back together without extra screws, etc.
 
Good luck.
 
--
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
bleachbot <bleachbot@httrack.com>: Jan 28 03:27AM +0100

Rheilly Phoull <rheilly@bigslong.com>: Feb 03 05:55AM +0800

On 02/02/15 9:52 PM, Tim R wrote:
 
> It's not clear to me if that circuit shows before the amplifier or after.
 
> If not, is there a better way to do this? Or better just not to do it at all?
 
> thanks,
 
The ccts shown are for inputs to the amp, you should be able to just use
one channel if you desire. Depending on the amp it may be possible to
bridge the outputs.
Rheilly Phoull <rheilly@bigslong.com>: Feb 03 06:01AM +0800

On 02/02/15 9:52 PM, Tim R wrote:
 
> It's not clear to me if that circuit shows before the amplifier or after.
 
> If not, is there a better way to do this? Or better just not to do it at all?
 
> thanks,
 
Very likely that if you feed the speaker from both + outputs (ie. do not
connect the - terminals just each + terminal) you will have the effect
you want.
Jeroni Paul <JERONI.PAUL@terra.es>: Feb 02 03:55PM -0800

Stereo to mono conversion is a dangerous process. There is a caveat: broadcasters often apply stereo wide expansion effects done by inverting one channel which do not add to mono very well. My all purpose safe solution is to take only the left channel and look in the device configuration for options to switch to mono.
 
I've lived that first hand. One user connected a cheap wireless headphone to a TV set. The headphones had a switch to set Normal (Stereo) mode or TV (Mono) mode, TV mode had to be used to stop a high pitch noise. The user complained that it worked fine most of the time but her favourite program would sound very faint and turning the volume up would result in very distorted sound. I found that switching the headphones to stereo would cure the problem but it resulted in the high pitched noise back. So that was it, that program was broadcast in wide stereo made by inverting one audio channel and the headphones summing of both channels resulted in almost no sound.
As a curiosity, enabling the TV builtin stereo enhacer did invert the situation: the affected program sounded good and any other had a very faint audio.
 
My solution: I disassembled the base station, unsoldered the right channel and connected the left channel to both inputs. Not a high tech solution but she was very happy with it.
dansabrservices@yahoo.com: Feb 02 04:32PM -0800

The simplest way to do this is to use an RCA Y adapter and connect the single input to both the left and right channels. This is a common practice and will not harm the unit. Any attempt to combine the separate outputs could result in damage to the amp. It was not designed to have that occur.
 
Pick up a y-cable. Should be less than $5.00
 
Dan
Scotophor <a.j.franzman@verizon.net>: Feb 02 03:17PM -0800

I'm seeking some out-of-production discrete through-hole component LED light bars for a project. There are two different styles that I want and can not substitute. According to a couple of archived internet postings, they were reportedly manufacturer-discontinued in either the late 1970s or early 1990s, but remained somewhat available until around 2000 because at least two distributors had bought the manufacturers' remaining stocks as surplus and sold them in retail packaging.
 
The first type have 2 LED emitters (a.k.a. chips, or dice) per unit. Their front face measures approximately 14 mm x 7 mm (9/16 x 1/4 inch) and they're about 12 mm (1/2 inch) tall excluding leads. They're made of lightly-tinted clear epoxy, with a white-ish diffusion layer about 1-2 mm (~1/16 inch) thick at the front. The dice are about 7 mm (1/4 inch) apart, center-to-center. These were once sold in retail packaging as Cal-Pak brand "Specialty LEDs", distributed by Cal West Supply, Inc. as their part numbers CP-59 (green), CP-58 (red) and CP-60 (yellow). I know that the Cal-Pak packages were stocked in MarVac Electronics stores in the Los Angeles, California vicinity, but I do not know where else they may have been found nor how widely distributed they were. They were also offered online via Cal West's website, www.hallbar.com (defunct since early 2005). Additionally, I've been told that these LEDs have been found in "Lucky Bag" LED assortments sold primarily in Europe several years ago by Kemo Electronic. Kemo still sells such assortments but this type is apparently no longer included. I do not know the original manufacturers' part numbers nor which company(/ies) made them, though I have read a post mentioning that they were Japanese.
 
The second type is of similar general appearance and construction, but they have 3 emitters per unit. Their front face measures about 18 mm x 5 mm (11/16 inch x 3/16 inch) and they're about 9 mm (3/8 inch) tall excluding leads. The chips are about 5 mm (3/16 inch) apart, center-to-center. These were also sold in Cal-Pak packaging, at least in green (CP-57) and red (CP-56) colors, but apparently not in yellow. There are similar LEDs to these in current production, but not exactly alike -- the chip-to-chip spacing is 6 mm now, and the dimensions a bit smaller at 16 mm length and 8 mm height. Some time circa 2000, Cal West switched the LEDs in their Cal-Pak packaging to the current style without changing the part numbers. They also changed the 2-die style to a much smaller modern type of only 10 mm x 5 mm frontal dimension, again without changing the part numbers.
 
Photos linked below show the original large 2-chip style (slightly retouched image of actual LEDs in all 3 colors), the original 3-chip style (the green one is real and the others are simulated), and the Cal-Pak blister card packaging (partly simulated -- I don't know how many actually came on a card; it would most likely have been in the range of 1 to 4).
 
At the time of posting this, I believe I have fairly well exhausted the online possibilities presented by the popular search engines. I'm also running several daily eBay searches in English and German. So, unless you have access to data that isn't generally available to the public or crawled by the search bots, or is in another language, please don't waste your time running internet searches on my behalf. I'm after real-world info about a source or possible sources for these LEDs that probably /isn't/ already online.
 
I will consider your offers for any quantity. I am willing to pay international shipping costs. I'm in southern California, U.S.A.
 
http://www.electro-tech-online.com/attachments/cp-59-58-60-png.89802/
http://www.electro-tech-online.com/attachments/cp-57-56-xx-png.89803/
http://www.electro-tech-online.com/attachments/cp-58-packaging_simulated-png.89804/
 
Reply here or to a.j.franzman [ A T ] verizon [ D O T ] net. You can also view a duplicate of this posting at http://www.electro-tech-online.com/threads/wanted-obsolete-component-led-rectangular-light-bars.143227/ and reply there.
"Ron D." <Ron.Dozier@gmail.com>: Feb 02 02:15PM -0800

switch specifications usuallyy have the following notoations
 
ON-(ON)-none
and shorting or make before break
thus an (ON)-none-ON switch would have 2 positions. One momentary and the other ON.
 
The notation of poles and throws are also used, thus SPDT is a single pole double throw (two positions).
 
Shorting switches were used in audio where both adjacent connections are made simultaneously for a brief instant to avoid pops. This is usually used for rotary switches.
 
Watch switch ratings: The AC and DC ratings can be very different.
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