sci.electronics.repair - 25 new messages in 13 topics - digest

sci.electronics.repair
http://groups.google.com/group/sci.electronics.repair?hl=en

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Today's topics:

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TOPIC: JOIN THIS WEB LINK EARN MORE
http://groups.google.com/group/sci.electronics.repair/t/7270f5b0082f857e?hl=en
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== 1 of 1 ==
Date: Fri, Jan 21 2011 3:13 am
From: kaniSH

http://123maza.com/35/phttp://www.PaisaLive.com/register.asp?1241138-3251643ower845

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TOPIC: Pet hates ?
http://groups.google.com/group/sci.electronics.repair/t/e7925b5c2233e9ec?hl=en
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== 1 of 4 ==
Date: Fri, Jan 21 2011 4:09 am
From: Ron

On 21/01/2011 10:13, Dave Plowman (News) wrote:
> In article<ihbg6q$ot5$1@news.eternal-september.org>,
> N_Cook<diverse@tcp.co.uk> wrote:
>> Last time I talked to him, late 2010, he mentioned he was starting a
>> range of "classic car" nuts and bolts , whatever that is, cannot find
>> mention on his site though
>
> In the UK, modern cars use metric threads. Ones from about after WW2 to
> the '80s mainly UNF and UNC. Pre WW2 BSW and BSF. BA was common for
> electrical stuff.
>
> A classic car is really just any which isn't recent and not defined under
> the strict headings of vintage etc. It isn't restricted to any make - just
> over 20 years old. Although that age isn't agreed by everyone.
>
Frosts carry an impressive range of useful bits and bobs for the
classic car restorer, their free catalogue is a good read

http://www.frost.co.uk

Ron

== 2 of 4 ==
Date: Fri, Jan 21 2011 4:22 am
From: "N_Cook"

Dave Plowman (News) <dave@davenoise.co.uk> wrote in message
news:519901728bdave@davenoise.co.uk...
> In article <ihbg6q$ot5$1@news.eternal-september.org>,
> N_Cook <diverse@tcp.co.uk> wrote:
> > Last time I talked to him, late 2010, he mentioned he was starting a
> > range of "classic car" nuts and bolts , whatever that is, cannot find
> > mention on his site though
>
> In the UK, modern cars use metric threads. Ones from about after WW2 to
> the '80s mainly UNF and UNC. Pre WW2 BSW and BSF. BA was common for
> electrical stuff.
>
> A classic car is really just any which isn't recent and not defined under
> the strict headings of vintage etc. It isn't restricted to any make - just
> over 20 years old. Although that age isn't agreed by everyone.
>
> --
> *Work like you don't need the money. Love like you've never been hurt.
>
> Dave Plowman dave@davenoise.co.uk London SW
> To e-mail, change noise into sound.

In the UK it probably means BSF and BSW threads perhaps brass or cyclo as
well

== 3 of 4 ==
Date: Fri, Jan 21 2011 4:37 am
From: b

On Jan 20, 2:38 pm, Lab1 <.@...> wrote:

> This is obviously made in China, everything is pretty crudely
> manufactured and assembled,

Most consumer electronics stuff these days is made in China! From low
end kit to decent, so you can't generalise that something made in
China is automatically shoddy.
Although a fair proportion is indeed cheap and disposable, that is the
case because they are responding to a demand. They only supply what
the west is prepared to pay for anyway!

Pet hates: excessive amounts of screws holding covers of TVs etc.
together. this seems to have got worse with flat panels.Often you
spend as much /more time assembling and re-asembling than the repair!

-B

== 4 of 4 ==
Date: Fri, Jan 21 2011 5:41 am
From: "Michael A. Terrell"

b wrote:
>
> On Jan 20, 2:38 pm, Lab1 <.@...> wrote:
>
> > This is obviously made in China, everything is pretty crudely
> > manufactured and assembled,
>
> Most consumer electronics stuff these days is made in China! From low
> end kit to decent, so you can't generalise that something made in
> China is automatically shoddy.
> Although a fair proportion is indeed cheap and disposable, that is the
> case because they are responding to a demand. They only supply what
> the west is prepared to pay for anyway!
>
> Pet hates: excessive amounts of screws holding covers of TVs etc.
> together. this seems to have got worse with flat panels.Often you
> spend as much /more time assembling and re-asembling than the repair!

Some large color TV consoles built in the '60s had 20 to 30 screws.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

==============================================================================
TOPIC: Yamaha PF 1000 piano , 2002
http://groups.google.com/group/sci.electronics.repair/t/2fdc9f41e99e9293?hl=en
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== 1 of 1 ==
Date: Fri, Jan 21 2011 4:26 am
From: "N_Cook"

Do they want repairers to use the included ,single, off-centre steel rod
prop, when the top is open , to slip out of the next to non existant holding
position on the floppy drive housing , so they do fatal damage when the
whole wooden top with main pcb and display etc, crashes down? A bit of a
workup disconnecting wiring looms and screening cover but a hell of a lot
safer for collateral damage and personal safety, totally removing the top
section.

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TOPIC: TV picture distorted
http://groups.google.com/group/sci.electronics.repair/t/ec61658f4376abe1?hl=en
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== 1 of 1 ==
Date: Fri, Jan 21 2011 4:39 am
From: b

On Jan 17, 3:11 am, "PE" <p...@ix.netcom.com> wrote:
> Hi all: My 15-yr old Toshiba 27" crt television has recently developed a
> problem which is that approx 15 minutes after being turned on, the picture
> bows inward on the left and right sides. Then, after a few more minutes,
> the picture resolves and returns to normal and remains perfect for the
> remaining time the tv is on. If the symptom described above means the crt
> is wearing out, so be it, the set will soon be history. However, I'm
> wondering whether some other, replaceable part, might be going bad and
> causing the temporarily distorted picture.
>
> Would appreciate any suggestions re. probable cause(s) of symptom described
> above. Am basically novice, but handy and with soldering skills, and have
> done a few simple tv repairs in the past. Thanks for your replies!

resolder the connections of the coils in the E-W correction circuit,
common fault. Nothing to do with the tube. Do be aware of high
voltages in tvs, see the www.repairfaq.org before proceeding.
good luck
-B

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TOPIC: Sanyo TV
http://groups.google.com/group/sci.electronics.repair/t/9e4c8f5b72f9e8d7?hl=en
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== 1 of 1 ==
Date: Fri, Jan 21 2011 4:43 am
From: b

On Jan 18, 6:30 am, Michael Gross <pigwigg...@yahoo.com> wrote:
> Michael A. Terrell wrote:
>
> > Yawn. Phil is in Australia. It's also where you should be. They
> > don't require you to have brains in the outback.
>
> If I had a fucking pig here, I would fucking kill it right here on
> camera. I don't give a fuck. I like to eat. Fuck him. I'll cut his
> throat with a knife, I'll do it with my teeth. I don't give a shit. I
> really don't give a fuck. That's what I think.

How did your pig slaughter /meal go? I'm intrigued. Post us some
images from your camera.

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TOPIC: Awesome speakers!!
http://groups.google.com/group/sci.electronics.repair/t/19ed616a0fe70f02?hl=en
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== 1 of 4 ==
Date: Fri, Jan 21 2011 5:02 am
From: Jeffrey Angus

On 1/21/2011 4:06 AM, JW wrote:
> I've always wondered (and dreamed) of a speaker cabinet made of granite or
> soapstone. With the right drivers, I'll bet they'd sound great.

I seem to remember Popular Electronics (I think) having
an article where you made the cabinets out of a section
of flue liner.

Jeff

== 2 of 4 ==
Date: Fri, Jan 21 2011 5:52 am
From: Jeff Liebermann

On Fri, 21 Jan 2011 07:02:59 -0600, Jeffrey Angus
<jangus@suddenlink.net> wrote:

>On 1/21/2011 4:06 AM, JW wrote:
>> I've always wondered (and dreamed) of a speaker cabinet made of granite or
>> soapstone. With the right drivers, I'll bet they'd sound great.
>
>I seem to remember Popular Electronics (I think) having
>an article where you made the cabinets out of a section
>of flue liner.

It was made from glazed tile sewer pipe. That was the DrainPipe 8
speaker.
<http://www.audioxpress.com/magsdirx/ax/addenda/media/weems_drainpipe8.pdf>
My father and I built one (not two as this was in the daze before
stereo). It think I was 15 or 16 years old at the time. I vaguely
recall that it sounded great, but my mother had aesthetic objections.
The sound also coupled nicely to the floor and neighbors downstairs
also voiced their objections. The only part I really remember was
watching someone haul off the monster to who knows where.

--
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 4 ==
Date: Fri, Jan 21 2011 6:43 am
From: Jeffrey Angus

On 1/21/2011 7:52 AM, Jeff Liebermann wrote:
> <jangus@suddenlink.net> wrote:
>> I seem to remember Popular Electronics (I think) having
>> an article where you made the cabinets out of a section
>> of flue liner.
>
> It was made from glazed tile sewer pipe. That was the DrainPipe 8
> speaker.

And then I found this...

> I think David Weems did something such as
> this in one of his speaker books from the
> 80s. If I recall, he used the chimney flues
> which were rectangular and had rounded
> corners. He cut the flue in half, making an
> angled cut, so each piece had a slanted
> front baffel, which was made of wood.

> From what I can remember, it made a great
> cabinet. I think it was Weems.

My memory served me well. He used 9"x13"x24" chimney flue tile, and cut
it in two, by making an angled cut, using a masonry blade attached to a
skil saw.

Reply With Quote

Jeff
the other other one.

== 4 of 4 ==
Date: Fri, Jan 21 2011 7:13 am
From: Chuck

On Thu, 20 Jan 2011 09:51:56 -0500, Archon
<Chipbee40_SpamNo@yahoo.com> wrote:

>On 1/20/2011 8:51 AM, Archon wrote:
>> On 1/20/2011 8:45 AM, William Sommerwerck wrote:
>>> Though I know you're kidding, I sincerely hope you're kidding about
>>> buying
>>> them.
>>>
>>> For what the speaker costs, and the profit they make on it, they could
>>> easily pay a native-English-speaking copywriter to create effective
>>> advertising. That they don't, shows they don't care what kind of image
>>> they
>>> present. I would not normally buy products from such a company.
>>>
>>> I loved the line about the effectiveness of biwiring in controlling
>>> back-EMF
>>> had been proved by lenz [sic]! (Lenz has been dead for some years.) In
>>> fact,
>>> biwiring should have no effect on the back-EMF "seen" by the amplfier.
>>>
>>> "But remember what it does when you block a bicycle pump at one side
>>> and you
>>> lower the handle. It gets more difficult to compress air. Well all other
>>> speakers have that problem!"
>>>
>>> No, they don't. Planar dipoles don't.
>>>
>>> If Tesla were alive, he'd probably sue for having his name attached to
>>> this
>>> product.
>>>
>>> I wish JGH were still alive, so I could call him and we could read the ad
>>> together, and laugh our heads off.
>>>
>>> If you have US$13K to spend on a speaker, you can buy something much
>>> better...
>>>
>>> http://www.quad-hifi.co.uk/ranges.php?sector_id=1
>>>
>>>
>> I don't have a spare $13K to spend on anything, let alone wasting it on
>> some hyped up bogus speaker, yes, William I was kidding ;-)
>> JC
>
>I was actually looking for some good speakers when I came across the ad,
>but seriously though, the whole audio sector is so overhyped, I know a
>couple of guys developing speakers, and the way they go on, its more
>magic than physics. I'd like to see a pro review of those speakers, they
>may well sound great, but so far I've not found anything. The Quads look
>good but again way out of my price range.
>JC

You might want to look at the higher end Paradigm speakers. Some of
their under $2k speakers sounded better than a $20k speaker we used to
sell at an upscale audio salon. Chuck

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TOPIC: OT? How did they do the double image on the Patti Duke show?
http://groups.google.com/group/sci.electronics.repair/t/40e332a7f10aa6b4?hl=en
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== 1 of 4 ==
Date: Fri, Jan 21 2011 5:26 am
From: mm

OT? How did they do the double image on the Patti Duke show?

Does anyone know how they showed two of her at the same time?
I'm watching reruns now on an 19" tv now, from one foot away, and I
can't see line or anything. Sometimes they just show the back of the
head of a double for the second one, but other times they show both of
them. Nothing shows and and I don't think they had green-screen
electronic technology then. Was there a physical or photographic
method of separating one moving image from its background and
superimposing it on another?

== 2 of 4 ==
Date: Fri, Jan 21 2011 6:03 am
From: Jeff Liebermann

On Fri, 21 Jan 2011 08:26:08 -0500, mm <NOPSAMmm2005@bigfoot.com>
wrote:

>OT? How did they do the double image on the Patti Duke show?
>
>Does anyone know how they showed two of her at the same time?
>I'm watching reruns now on an 19" tv now, from one foot away, and I
>can't see line or anything. Sometimes they just show the back of the
>head of a double for the second one, but other times they show both of
>them. Nothing shows and and I don't think they had green-screen
>electronic technology then. Was there a physical or photographic
>method of separating one moving image from its background and
>superimposing it on another?

Split screen:
<http://en.wikipedia.org/wiki/Split_screen_%28film%29>

Rita McLaughlin sometimes played the identical twin:
<http://en.wikipedia.org/wiki/The_Patty_Duke_Show#Visual_effects>
<http://en.wikipedia.org/wiki/Rita_McLaughlin>

--
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 4 ==
Date: Fri, Jan 21 2011 6:48 am
From: nesesu

On Jan 21, 5:26 am, mm <NOPSAMmm2...@bigfoot.com> wrote:
> OT? How did they do the double image on the Patti Duke show?
>
> Does anyone know how they showed two of her at the same time?
> I'm watching reruns now on an 19" tv now, from one foot away, and I
> can't see line or anything. Sometimes they just show the back of the
> head of a double for the second one, but other times they show both of
> them. Nothing shows and and I don't think they had green-screen
> electronic technology then. Was there a physical or photographic
> method of separating one moving image from its background and
> superimposing it on another?

Look to see if there is ever any overlap. If the two images are always
left screen/right screen with a gap between, then it is likely simple
split screen. If it is done well, the only indication is an occasional
shadow cut off at the 'dodged' [fuzzed] boundry. Early 'blue screen'
had problems with the edges so it was usually fairly obvious.

Neil S.

== 4 of 4 ==
Date: Fri, Jan 21 2011 7:22 am
From: "William Sommerwerck"

> Split screen:
> http://en.wikipedia.org/wiki/Split_screen_%28film%29

This article is incomplete. Split screen was traditionally done in-camera,
using a "matte box". This device -- which is basically a black-painted box
resembling a rectangular lens shade -- sits in front of the camera and
blocks half the image. Once the actor has performed one role, the film is
rewound and the matte box flipped. The edge of the box is tapered in such a
way that there is a gradual, calculated fall-off in light intensity at the
inner edge, allowing the images to blend without an obvious "seam".

One of the most-famous uses of matte-box split screen occurs in Buster
Keaton's "The Playhouse", where he appears nine times in the same scene!

http://en.wikipedia.org/wiki/The_Playhouse_%28film%29

It's also possible to create a dynamic split screen in an optical printer.
This was most-famously done in "Bringing Up Baby", where we see Cary Grant
leave Katherine Hepburn's apartment, followed (IIRC) by George, then Baby.
As it would have been extremely difficult to choreograph/synchronize the
movements of the animals, this scene was printed from three strips of film.
If you look closely, you can see the join line moving across the image.

Digital technology makes split-screen effects almost trivial. The first time
I saw a digital split screen was in an episode of ST:TNG where a character
materialized from the transporter, then moved across the image without a
cut. My jaw hung open for a few seconds, because I knew that wasn't possible
in-camera. I then realized how it had to have been done.

Digital split screen is extremely flexible, because the dividing line can
have any shape and be anywhere in the image, and can move or change shape
from frame to frame.

Split-screen devices have been made for still cameras, most notably
Polaroids.

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TOPIC: Cell phone data plan
http://groups.google.com/group/sci.electronics.repair/t/8974e71ed0054784?hl=en
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== 1 of 2 ==
Date: Fri, Jan 21 2011 5:48 am
From: Lab1 <.@...>

On 1/20/2011 10:07 PM, LSMFT wrote:
> If I have cell phone usb stick for wireless data connection can I use
> Magic Jack phone service on my notebook?

I don't see why not. If you can use Skype you can use Magic Jack as they
are pretty close to the same technology less Magic Jacks DTMF telephone
interface.

--
-Scott

== 2 of 2 ==
Date: Fri, Jan 21 2011 6:17 am
From: "Michael A. Terrell"

Lab1 wrote:
>
> On 1/20/2011 10:07 PM, LSMFT wrote:
> > If I have cell phone usb stick for wireless data connection can I use
> > Magic Jack phone service on my notebook?
>
> I don't see why not. If you can use Skype you can use Magic Jack as they
> are pretty close to the same technology less Magic Jacks DTMF telephone
> interface.

Have you ever used a Magic Jack? The audio is clear, but there is a
lot of latency.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

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TOPIC: Are CRT monitor registers standardized?
http://groups.google.com/group/sci.electronics.repair/t/c82cfde479e993f8?hl=en
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== 1 of 1 ==
Date: Fri, Jan 21 2011 5:48 am
From:

whit3rd, thanks. Very useful info.

Apologies for the top post.

Mike

"whit3rd" <whit3rd@gmail.com> wrote in message news:ecbcff92-b87e-4405-a617-3a45b86bcdf3@o9g2000pre.googlegroups.com...
On Jan 20, 6:44 am, <nos...@nospam.invalid> wrote:
> Hi all, I used WinDAS to adjust G2 on an overbright Sony F500R monitor, and want to learn about a few of the other registers,
> especially 22-38 and the relationships between them (full dump copied below). Google was useless.
>
> In general are these registers standard across monitor manufacturers?

Some names are familiar.
Your "G2" means the second grid of the CRT, and determines
the overall brightness (and needs correction often as the tube ages).
A 'readjustment' of a color monitor is potentially complex, it seems
like most things we used to do with screwdrivers are now 0-255 range
binary numbers, probably for one or several 8-bit DACs.

(about registers 28-33)
Red, green, blue blanking levels (the cutoff 'black' setting) might
have a 'center' value so one can start the adjustment procedure
at a neutral value (we used to center the ranges first, set G2 or
"screen" and go from there). The "max" might mean maximum
value of the voltage, not necessarily maximum integer in the
DAC register...

then when the 'zero' brightness values are set you adjust gains
of the video amplifiers, i.e. 'drive'
(registers 22...27)

Sizing and centering the screen with (104...107)

Pincushion and pincushion balance adjustments(108...109) are
for barrel distortion (or inverse barrel == pincushion)

Keystone (get this wrong and the rectangles come out as rhombuses)
(110...111)

> REG# ** LABEL ** VALUE NOTES
> 1 ** G2 ** 115 Factory setting (139) caused overbrightness
> 2 ** DRV_ZERO_LEVEL ** 0
> 3 ** DRIVE_MIN ** 0
> 4 ** DRIVE_MAX ** 250
> 5 ** dummy4 ** SKIP
> 6 ** dummy5 ** SKIP
> 7 ** SRGB_CONT ** 225
> 8 ** SRGB_BRT ** 75
> 9 ** dummy8 ** SKIP
> 10 ** dummy9 ** SKIP
> 11 ** dummy10 ** SKIP
> 12 ** dummy11 ** SKIP
> 13 ** dummy12 ** SKIP
> 14 ** REG13 ** 2
> 15 ** REG14 ** 2
> 16 ** REG15 ** 0
> 17 ** OSD_ENLARGE_LIN ** 102
> 18 ** REG17 ** 35
> 19 ** REG18 ** 177
> 20 ** REG19 ** 37
> 21 ** REG20 ** 80
> 22 ** R_DRV_CONT_MIN ** 200
> 23 ** R_DRV_CONT_MAX ** 200
> 24 ** G_DRV_CONT_MIN ** 150
> 25 ** G_DRV_CONT_MAX ** 150
> 26 ** B_DRV_CONT_MIN ** 150
> 27 ** B_DRV_CONT_MAX ** 150
> 28 ** R_BKG_BRT_CENT ** 100
> 29 ** R_BKG_BRT_MAX ** 86
> 30 ** G_BKG_BRT_CENT ** 140
> 31 ** G_BKG_BRT_MAX ** 125
> 32 ** B_BKG_BRT_CENT ** 125
> 33 ** B_BKG_BRT_MAX ** 105
> 34 ** CONT_MIN ** 30
> 35 ** CON_MAX_BR_CENT ** 150
> 36 ** CON_MAX_BRT_MAX ** 115
> 37 ** BRIGHTNESS_CENT ** 125
> 38 ** BRIGHTNESS_MAX ** 170
> 39 ** R_USER_DRIVE ** 151
> 40 ** G_USER_DRIVE ** 139
> 41 ** B_USER_DRIVE ** 142
> 42 ** R_USER_BKG ** 128
> 43 ** G_USER_BKG ** 128
> 44 ** B_USER_BKG ** 128
> 45 ** REG44 ** 60
> 46 ** USER_COLOR_FLAG ** 2
> 47 ** H_FREQ ** 1078
> 48 ** COLOR_MODE ** 1
....
> 100 ** SIGNAL_INDEX ** 17
> 101 ** V_BLK_WIDTH_MIN ** 115
> 102 ** V_BLK_WIDTH_MAX ** 115
> 103 ** REG102 ** 115
> 104 ** H_PHASE ** 149
> 105 ** H_SIZE ** 114
> 106 ** V_CENTER ** 148
> 107 ** V_SIZE ** 132
> 108 ** PIN ** 136
> 109 ** PIN_BAL ** 128
> 110 ** KEY ** 128
> 111 ** KEY_BAL ** 128
> 112 ** MOIRE_CANCEL_SW ** 0
> 113 ** MOIRE_LEVEL ** 0
... and lots more...

==============================================================================
TOPIC: Nickel plated polyimide--where to get?
http://groups.google.com/group/sci.electronics.repair/t/8bee83d05dbdcb50?hl=en
==============================================================================

== 1 of 2 ==
Date: Fri, Jan 21 2011 5:57 am
From: Glen Walpert

On Thu, 20 Jan 2011 23:32:53 -0500, Phil Hobbs wrote:

> I have a partly-baked idea for improving temperature controllers, but it
> requires a bunch of nickel plated polyimide film--say 3 to 8 mils thick,
> with 40 microinches of electroless nickel on it.
>
> I need to pattern it and then solder to it. Copper is too conductive,
> which is a pity, since I already have a roll of polyimide with 1/2 oz Cu
> on it.
>
> I haven't found anybody that's interested in supplying it in engineering
> quantities (say 10 square feet).
>
> Anyone here have a favourite shop that does nickel plating on plastic?
>
> Thanks
>
> Phil Hobbs

Not sure about the nickel, but Minco will do custom polyimide film
heaters to your design:

http://www.minco.com/products/heaters.aspx?id=71

== 2 of 2 ==
Date: Fri, Jan 21 2011 7:37 am
From: Phil Hobbs

Glen Walpert wrote:
> On Thu, 20 Jan 2011 23:32:53 -0500, Phil Hobbs wrote:
>
>> I have a partly-baked idea for improving temperature controllers, but it
>> requires a bunch of nickel plated polyimide film--say 3 to 8 mils thick,
>> with 40 microinches of electroless nickel on it.
>>
>> I need to pattern it and then solder to it. Copper is too conductive,
>> which is a pity, since I already have a roll of polyimide with 1/2 oz Cu
>> on it.
>>
>> I haven't found anybody that's interested in supplying it in engineering
>> quantities (say 10 square feet).
>>
>> Anyone here have a favourite shop that does nickel plating on plastic?
>>
>> Thanks
>>
>> Phil Hobbs
>
> Not sure about the nickel, but Minco will do custom polyimide film
> heaters to your design:
>
> http://www.minco.com/products/heaters.aspx?id=71

Thanks, I asked them already--they aren't interested in supplying plain
sheets.

I thought about vacuum dep, but it'll get expensive in the sort of
quantity I want, and there's still the adhesion issue. If I still had
my own evaporator, I'd probably do it that way--I could just wrap the PI
round the inside of the bell jar!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058

email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net

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

== 1 of 2 ==
Date: Fri, Jan 21 2011 6:46 am
From: PeterD

On Wed, 19 Jan 2011 17:59:29 -0800, David Nebenzahl
<nobody@but.us.chickens> wrote:

>On 1/19/2011 12:55 PM mike spake thus:
>
>> PeterD wrote:
>>
>>> On Wed, 19 Jan 2011 05:55:03 -0800, "William Sommerwerck"
>>> <grizzledgeezer@comcast.net> wrote:
>>>
>>>>>> Can you return the oven? You can use the argument that it's
>>>>>> not fit for its intended purpose. Which it isn't.
>>>>>
>>>>> Nope, my inability to forecast the consequences is not the
>>>>> fault of the seller.
>>>>
>>>> If your description is correct, the oven is grossly misdesigned.
>>>> You do not implement variable power by turning the magenetron on
>>>> for 15 seconds, then letting it sit for a minute! I've /never/
>>>> seen a microwave oven that works that way. My home GE works fine,
>>>> as do all those I've seen where I've worked.
>>>
>>> Huh? Virtually all the ones I've seen do just that: run a 10 to 15
>>> second on/off time cycle. The magnetron is turned on with a relay,
>>> so rapid cycling just begs to blow that relay.
>>
>> It's worse than that. A triac can fix the relay issue. The problem
>> is the thermal time constant of the magnetron filament.
>
>I guess I'm showing my ignorance here, as I don't know much about
>magnetrons, but why can't you just let the filament burn while you cycle
>the HV, like you'd do with any other ordinary tube? I mean, with other
>tubes, it's OK to apply power to the heater without any anode voltage,
>right?

The filament is a minor current, the main HV voltage is the issue. To
cycle off the transformer rapidly with a relay would likely result in
a relay lifetime of a few weeks at best.

I don't believe there ever was an issue with the filaments.

I agree, a triac could possibly be used, though you are talking about
swtiching as much as 1500 watts, inductive (because of the
transformer). Might be too expensive to find a triac that will take
that kind of abuse and survive!

== 2 of 2 ==
Date: Fri, Jan 21 2011 6:47 am
From: PeterD

On Thu, 20 Jan 2011 21:50:04 -0800, isw <isw@witzend.com> wrote:

>In article <4d3796cb$0$2374$822641b3@news.adtechcomputers.com>,
> David Nebenzahl <nobody@but.us.chickens> wrote:
>
>> On 1/19/2011 12:55 PM mike spake thus:
>>
>> > PeterD wrote:
>> >
>> >> On Wed, 19 Jan 2011 05:55:03 -0800, "William Sommerwerck"
>> >> <grizzledgeezer@comcast.net> wrote:
>> >>
>> >>>>> Can you return the oven? You can use the argument that it's
>> >>>>> not fit for its intended purpose. Which it isn't.
>> >>>>
>> >>>> Nope, my inability to forecast the consequences is not the
>> >>>> fault of the seller.
>> >>>
>> >>> If your description is correct, the oven is grossly misdesigned.
>> >>> You do not implement variable power by turning the magenetron on
>> >>> for 15 seconds, then letting it sit for a minute! I've /never/
>> >>> seen a microwave oven that works that way. My home GE works fine,
>> >>> as do all those I've seen where I've worked.
>> >>
>> >> Huh? Virtually all the ones I've seen do just that: run a 10 to 15
>> >> second on/off time cycle. The magnetron is turned on with a relay,
>> >> so rapid cycling just begs to blow that relay.
>> >
>> > It's worse than that. A triac can fix the relay issue. The problem
>> > is the thermal time constant of the magnetron filament.
>>
>> I guess I'm showing my ignorance here, as I don't know much about
>> magnetrons, but why can't you just let the filament burn while you cycle
>> the HV, like you'd do with any other ordinary tube? I mean, with other
>> tubes, it's OK to apply power to the heater without any anode voltage,
>> right?
>
>Not sure about the ones used in uwave ovens, but with some magnetrons,
>once they get going, the filament power has to be reduced (sometimes to
>zero) because the filament is heated by the impact of accelerated
>electrons banging into it.
>

Neat trick since the filament emitts teh electrons...

==============================================================================
TOPIC: Fender Frontman 212R amp, 2010
http://groups.google.com/group/sci.electronics.repair/t/b4d6a83c2aaabd02?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jan 21 2011 6:49 am
From: "N_Cook"

Yes, just out of warranty, even if in warranty little point in an exchange
because the same would likely occur a year after that. Of course yet again
recent made in China for USA and then export to here UK, so absolutely no
mention of RoHs / PbF anywhere - anyone the definitive answer? I've not
taken appart to the solder side yet.

aside
[see this thread a week ago , uk.legal.moderated/title "failed /
unrepairable goods - what are my options? (if any)"
no mention of pbfitis there but PbF a likely cause. ]

This Fender - low level domestic use and failed to no output , no hiss or
anything, during usual low volume use. Both // speakers are o/c , I suspect
cutting into the dome of each will show the usual , these days, failed PbF
at the tail/VC wire union. One must have quietly failed unnoticed and then
the second , I don't expect to see burnt coils if I explore that far . Will
of course check for o/p DC or ultrasonic but no reported magic smoke/smells
or noise or signs of excess heat.
The killer ;-( is the mains transformer is only hanging in there on a wing
and a prayer - 3 of the 4 retaining nuts dropped off, fourth totally loose
and primary tail mains-wire rubbing on the abrasive ceramic edge of a 5W W/W

==============================================================================
TOPIC: USA free classifieds for advertising !!! Just free for you !!!
http://groups.google.com/group/sci.electronics.repair/t/4f2a36b3ac6c1098?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jan 21 2011 6:50 am
From: Marrina anderson tina

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