sci.electronics.repair - 22 new messages in 9 topics - digest

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

sci.electronics.repair@googlegroups.com

Today's topics:

==============================================================================
TOPIC: Type of ceramic wirewound resistor?
http://groups.google.com/group/sci.electronics.repair/t/24e3fe2e41d78acc?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 15 2011 12:20 am
From: "N_Cook"

nesesu <neil_sutcliffe@telus.net> wrote in message
news:8b8b00d5-77b4-463e-8bc6-3d43637d602a@w23g2000vbx.googlegroups.com...
On Oct 13, 5:58 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
> <snip>
>
> >> > I must be missing something here , what is the point of the spring
off
> >> > disconnect?
>
> >> It opens the resistor, and removes power from the overload condition
that
> >> it's there to protect against ...
>
> >> Arfa
>
> > But not if you "weld" it shut with high melting point solder
>
> What are you saying exactly ? That 'high melting point' solder was not
what
> was originally used to hold it shut by the manufacturers ? Are you
> suggesting that a company the size of Rediffusion, who designed their own
TV
> sets making use of these devices, then went on to encourage their
(extremely
> well trained and well thought of in the trade) engineers, to execute some
> kind of bodge repair on ones that had opened ?
>
> No, of course they didn't. If that material is what central stores
supplied
> to the branches for remaking the spring connection, then I think you can
be
> pretty sure that it was appropriate for the job. Presumably, as you found
it
> necessary to ask what one of these resistors was in the first place, you
> have no experience of them, contemporary with the time that they were
> commonly in use ?
>
> Arfa
>
>
>
> - Hide quoted text -
>
> - Show quoted text -

Perhaps N-Cook was thinking of the similar over temperature cutouts
used to protect transformers such as used in Philips Tape recorders
that used a very low temperature 'solder' to hold the spring
connection together.
This type of 'fusable link' has been used for well over 100 years and
uses very carefully formulated alloy as the sensor to operate at
remarkably precise temperatures. The fire sprinkler head is one of the
earliest mass produced applications of this technique.

Neil S.

+++++

Someone upthread mentiond a currently available type of them
http://www.vishay.com/docs/21008/kk.pdf
page 41 top left has a spring open view of the sprung type
and top right of p42 has the derating plot showing the maximum operating
temperature of 150 degrees for the spring type , compared to 350 degrees for
the non-safety, plain vanilla ones

==============================================================================
TOPIC: Tips for saving ancient loudspeakers?
http://groups.google.com/group/sci.electronics.repair/t/47e1ea90a9d3138f?hl=en
==============================================================================

== 1 of 4 ==
Date: Sat, Oct 15 2011 12:36 am
From: "N_Cook"

Anyone aware of a site of such tips for renovation.
About 50 years old. Looks as though the card of the cone hase weakened with
age, probably like the paper of books goes brown and crumbly over time.
Looks as though the central cone area probably has failed to resist the
returning force of the periphery and the spider and has buckled torsionally
but not split in that inner zone ,one or so inches, from the voice coil join
and radially out.

== 2 of 4 ==
Date: Sat, Oct 15 2011 7:17 am
From: "Michael A. Terrell"

N_Cook wrote:
>
> Anyone aware of a site of such tips for renovation.
> About 50 years old. Looks as though the card of the cone hase weakened with
> age, probably like the paper of books goes brown and crumbly over time.
> Looks as though the central cone area probably has failed to resist the
> returning force of the periphery and the spider and has buckled torsionally
> but not split in that inner zone ,one or so inches, from the voice coil join
> and radially out.

Recone the thing.

--
You can't have a sense of humor, if you have no sense.

== 3 of 4 ==
Date: Sat, Oct 15 2011 9:29 am
From: spamtrap1888

On Oct 15, 12:36 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> Anyone aware of a site of such tips for renovation.
> About 50 years old. Looks as though the card of the cone hase weakened with
> age, probably like the paper of books goes brown and crumbly over time.
> Looks as though the central cone area probably has failed to resist the
> returning force of the periphery and the spider and has buckled torsionally
> but not split in that inner zone ,one or so inches, from the voice coil join
> and radially out.

If you attempt to splint or reinforce that area, perhaps with a collar
of paper, you will change the mass and thus lower the output. If the
speaker is meant to reproduce a wide frequency range, it will no
longer go up as high in frequency.

Acoustic design of speaker cones relies on the shape of the cone and
the material from which it's made. Speakers meant to be woofers only
are the least demanding -- you merely have to get the mass right.
Midrange and full range speaker performance depends largely on the
diaphragm material.

== 4 of 4 ==
Date: Sat, Oct 15 2011 10:39 am
From: gregz

"N_Cook" <diverse@tcp.co.uk> wrote:
> Anyone aware of a site of such tips for renovation.
> About 50 years old. Looks as though the card of the cone hase weakened with
> age, probably like the paper of books goes brown and crumbly over time.
> Looks as though the central cone area probably has failed to resist the
> returning force of the periphery and the spider and has buckled torsionally
> but not split in that inner zone ,one or so inches, from the voice coil join
> and radially out.

Does it play? I would have to see it.

Greg

==============================================================================
TOPIC: Site to open blocked sites, and prohibited and encoded
http://groups.google.com/group/sci.electronics.repair/t/3fb8d37a4e78c393?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 15 2011 1:56 am
From: porxy

Site to open blocked sites, and prohibited and encoded

http://myway.x90x.net/

==============================================================================
TOPIC: Sony CDX-C5000 head unit, TUX-020 tuner module failure
http://groups.google.com/group/sci.electronics.repair/t/92a5f0f54c6a56ca?hl=en
==============================================================================

== 1 of 4 ==
Date: Sat, Oct 15 2011 2:26 am
From: Clyde

Hi.

I have 2 Sony Car Audio head units both with faulty tuner modules. The
module is labelled TUX-020, and is listed online simply as "mounted
circuit board", it is also no longer available. I am able to get
schematics for the main unit, but this does not include any details of
the tuner block at all. I suspect Sony regarded it as a "black box".

One of the units tunes to AM stations fine, but FM reception is
extremely faint, barely audible behind the background noise. The tuning
voltage does sweep when I do a seek, and since the local stations are
faintly audible I suspect some failure in the front-end.

The second unit does not tune at all, though noise is present and
changes when an aerial is inserted. On this one the tuning voltage
remains high and does not sweep at all, obviously no reception on any band.

Car aerial has been confirmed good with a working unit. I have swapped
the tuner modules between the head units and the fault travels with the
module, confirming that the fault is with the module itself.

Does anyone have a schematic for this module? Failing that does anyone
have an old head unit with a good module (possibly one with a faulty CD
mechanism or output stage)? Or possibly some idea of where to start
fault finding? There are a lot of models from this vintage (around 1999)
which appear to use this module. If it's any help in identification, the
unit is a face-off with CD/MD changer control.

I would just buy a new head unit, but I have a 10 disc CD changer fitted
to the vehicle which is in good working order.

== 2 of 4 ==
Date: Sat, Oct 15 2011 3:08 am
From: "N_Cook"

Clyde <mkdrummeyNOSPAMPLEASE@hotmail.com> wrote in message
news:ulcmq.10$UN2.4@newsfe04.ams2...
> Hi.
>
> I have 2 Sony Car Audio head units both with faulty tuner modules. The
> module is labelled TUX-020, and is listed online simply as "mounted
> circuit board", it is also no longer available. I am able to get
> schematics for the main unit, but this does not include any details of
> the tuner block at all. I suspect Sony regarded it as a "black box".
>
> One of the units tunes to AM stations fine, but FM reception is
> extremely faint, barely audible behind the background noise. The tuning
> voltage does sweep when I do a seek, and since the local stations are
> faintly audible I suspect some failure in the front-end.
>
> The second unit does not tune at all, though noise is present and
> changes when an aerial is inserted. On this one the tuning voltage
> remains high and does not sweep at all, obviously no reception on any
band.
>
> Car aerial has been confirmed good with a working unit. I have swapped
> the tuner modules between the head units and the fault travels with the
> module, confirming that the fault is with the module itself.
>
> Does anyone have a schematic for this module? Failing that does anyone
> have an old head unit with a good module (possibly one with a faulty CD
> mechanism or output stage)? Or possibly some idea of where to start
> fault finding? There are a lot of models from this vintage (around 1999)
> which appear to use this module. If it's any help in identification, the
> unit is a face-off with CD/MD changer control.
>
> I would just buy a new head unit, but I have a 10 disc CD changer fitted
> to the vehicle which is in good working order.

From my experience on
http://www.divdev.fsnet.co.uk/repair5.htm
probably not the TUX but some sort of firmware problem or a problem on the
front panel if its like those Sony XR-C5300
cant help more than that , its a "repair" job that got away

== 3 of 4 ==
Date: Sat, Oct 15 2011 9:49 am
From: "William R. Walsh"

Hi!

> From my experience onhttp://www.divdev.fsnet.co.uk/repair5.htm
> probably not the TUX but some sort of firmware problem or a problem on the
> front panel if its like those Sony XR-C5300
> cant help more than that , its a "repair" job that got away

A friend of mine was repairing a radio using a similar TEA-series IC.
I don't recall the exact details, but the IC "seemed" to be doing most
of the right things while reception just never happened. When audio
did come through the set, there was a lot of hash and other noise in
the signal. Every other piece of circuitry checked out.

He replaced the IC and the radio sprang immediately back to life.

William

== 4 of 4 ==
Date: Sat, Oct 15 2011 2:47 pm
From: Clyde

On 15/10/2011 17:49, William R. Walsh wrote:
> Hi!
>
>> From my experience onhttp://www.divdev.fsnet.co.uk/repair5.htm
>> probably not the TUX but some sort of firmware problem or a problem on the
>> front panel if its like those Sony XR-C5300
>> cant help more than that , its a "repair" job that got away
>
> A friend of mine was repairing a radio using a similar TEA-series IC.
> I don't recall the exact details, but the IC "seemed" to be doing most
> of the right things while reception just never happened. When audio
> did come through the set, there was a lot of hash and other noise in
> the signal. Every other piece of circuitry checked out.
>
> He replaced the IC and the radio sprang immediately back to life.
>
> William

I have to say I am suspicious of the i.c, as initial comparisons between
the 2 modules don't show any notable differences in component values.
The i.c itself seems to handle virtually everything aside from the tuned
circuits. I am suspicious that I have 2 faulty chips, one with an RF
amplifier or AGC fault or something along those lines, the other with a
fault in the tuning section.

I may well see if I can grab the i.c. and try it if it's cheap enough.
It may be difficult soldering up since there are quite a few large
components around it, which may make access awkward.

Thanks for the info

==============================================================================
TOPIC: White LED spectrum?
http://groups.google.com/group/sci.electronics.repair/t/7b379dacdacd2dfe?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Oct 15 2011 3:39 am
From: Salmon Egg

In article
<0001HW.CABDFC87000B6522B02069DF@news.eternal-september.org>,
Paul Conners <pconners98@gUSmail.com> wrote:

> Would like to find white SMD LEDs suitable for use as backlight for LCD
> monitors where the CCFL lamps have burned out. So need is for consistency
> between units and... well, "whiteness". ;-)
>
I really have no help for the question asked, but I think people
interested in the subject may have an answer to one of my questions.

I have a relatively new Samsung LCD monitor using LED back lighting.
When the computer is not providing a signal, such as waking from sleep,
I see a speckling or snow rather than steady background light. I have
two competing explanations.

1. The LED light is sufficiently spatially coherent to generate "laser
speckle." For example, you can see colored speckle in your fingernail
when illuminated by the sun. At one time I saw laser speckle from a
noble gas laser providing a mixture of lines that gave white looking
light.

2. With no signal, the noise in the video line was amplified in the
monitor circuitry. The display was presenting this as a fine churning
snow. When the computer finally was sending a signal, the pixels were
either fully on or fully off.

Does anyone have bette insight on this matter than I do?

Sam

Conservatives are against Darwinism but for natural selection.
Liberals are for Darwinism but totally against any selection.

== 2 of 3 ==
Date: Sat, Oct 15 2011 9:58 am
From: "William Sommerwerck"

"White" LEDs are actually blue LEDs with a phosphor that glows yellow under
blue light. The eyes sees blue + yellow = white.

Their spectrum is anything but continuous -- or even peaked at the right
points -- so it's highly unlikely to work.

== 3 of 3 ==
Date: Sat, Oct 15 2011 12:06 pm
From: Rich Webb

On Sat, 15 Oct 2011 09:58:38 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>"White" LEDs are actually blue LEDs with a phosphor that glows yellow under
>blue light. The eyes sees blue + yellow = white.
>
>Their spectrum is anything but continuous -- or even peaked at the right
>points -- so it's highly unlikely to work.

Most white LEDs are phosphor-based but hardy as bi-chromatic as you make
them sound. The little Cree in my pocket flashlight has the typical
broad peak around 450 nm and valley around 485 but it's quite continuous
down to 650, tailing off at about 670. Very different from the narrow,
discrete lines from a CCFL.

--
Rich Webb Norfolk, VA

==============================================================================
TOPIC: vizio tv
http://groups.google.com/group/sci.electronics.repair/t/fe5b8f308bd7494e?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Oct 15 2011 4:45 am
From: "Vince Schmitt"

Hi
I have a Vizio TV MDL VW37L HDTV20A
The pilot light is on (orange) push the power button and nothing
happens, the light stays orange, the set is dead, I tried a new power
supply board and still the same thing.
Thanks for any help I can get.
Vince
vschmitt29@gmail.com

== 2 of 3 ==
Date: Sat, Oct 15 2011 10:00 am
From: "William Sommerwerck"

If a new, good PS board doesn't fix it, then it's likely there's a short on
one of the other boards that's pulling down the voltage and keeping the
supply from turning on.

== 3 of 3 ==
Date: Sat, Oct 15 2011 3:52 pm
From: PlainBill@yawhoo.com

On Sat, 15 Oct 2011 05:45:06 -0600, "Vince Schmitt"
<vschmitt29@gmail.com> wrote:

>Hi
>I have a Vizio TV MDL VW37L HDTV20A
> The pilot light is on (orange) push the power button and nothing
>happens, the light stays orange, the set is dead, I tried a new power
>supply board and still the same thing.
> Thanks for any help I can get.
> Vince
>vschmitt29@gmail.com
Probably a problem with the main board. Some models of Vizio are
notorius for a failure of U33 (a AS1117 voltage regulator) on the main
board.

More information is available at www.badcaps.net/forum

PlainBill

==============================================================================
TOPIC: Tektronix TDS-744A SPC fails
http://groups.google.com/group/sci.electronics.repair/t/b56d00cbbdb41f12?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 15 2011 8:18 am
From: Andy Cuffe

On Fri, 14 Oct 2011 22:04:54 +0200, Reinhard Zwirner
<reinhard.zwirner@t-online.de> wrote:

>Andy Cuffe schrieb:
>
>May I dare to direct you to the Tek Scopes Yahoo group? You'll find a
>lot of Tek specialists there.
>
>HTH
>
>Reinhard

That's worth a try. I'm waiting for them to approve me now.

As a side question, has anyone here ever removed the LCD color shutter
from the CRT? I have two similar scopes (a 544 and 744). The 544 has
a mint CRT, but there are some bad spots on the shutter. The 744 has
a lot of burn in, but a perfect shutter. I would like to swap the
good shutter onto the good CRT, but only if I can expect the results
to be good.

==============================================================================
TOPIC: Sherwood RX-5502 Receiver Protection Shutdown, Repair, thoughts wanted..
.
http://groups.google.com/group/sci.electronics.repair/t/ba9b4799ea243157?hl=en
==============================================================================

== 1 of 2 ==
Date: Sat, Oct 15 2011 10:00 am
From: "William R. Walsh"

Hi!

> These Murata parts are about $4.50 each in onesies, through Mouser.

If I've found the right part, I reckon you are speaking of the 7812SR/
SRH-C regulators. These look like interesting devices but the low
current rating may be a problem. I need to rig up a way to see what
the current draw actually is.

I don't think noise in the circuit would be a problem, this regulator
appears to be powering a protection circuit. I've not traced the
circuit to know exactly what it's powering beyond that.

William

== 2 of 2 ==
Date: Sat, Oct 15 2011 1:34 pm
From: Uffe Bærentsen

Den 12-10-2011 19:05, William R. Walsh skrev:
> Hello all...
>
> This is part of a longer story which I won't get into now. Suffice it
> to say that I've wanted to get my hands on a failed Sherwood RX-4105
> or RX-4109 stereo receiver to see just what it is that kills
> them...abuse, misuse, weak parts, bad engineering/quality control or
> something else. I've never had any luck coming into a truly broken
> one, but someone recently gave me an RX-5502 that would just shut down
> right after power on. I've been very happy with all of the RX-4105 and
> 4109 units I own.
>
> The RX-5502 is a so-called multi-zone receiver. That is to say it can
> support up to eight connected pairs of speakers, with four of the
> pairs playing a different ("room 2") source if that is desired. It has
> two complete stereo amplifiers in place, each one claimed to have an
> output power of 100 watts per channel. (Obviously they're dreaming if
> they think that this receiver is ever going to output 400 total watts
> of power without catching fire, but...) This example was manufactured
> sometime in 2008.
>
> As found, this set would indeed power on for a few seconds, and shut
> down with a blinking standby LED. I started checking things out. In
> this set, the amplifier board is separate from the main board, so this
> was not terribly hard to do. Every power device tested good with a
> simple ohmmeter check, and nothing looked burnt or distressed on the
> amp board. This doesn't look like a case of a failed power transistor
> to me.
>
> I'm working without service literature or even a schematic as Sherwood
> would not provide them, but there is printing on the board that
> identifies what each conductor in the ribbon cable going to the amp
> board is used for. This set has a "test mode", and unlike similar
> models, the "test mode" allows the power to stay on indefinitely while
> the display test is running. Testing for voltages is a lot nicer
> without having to constantly turn the set back on again! Voltages are
> what I'd expect for B+ and B-, but a twelve volt input to the board is
> hovering around a few hundred millivolts at most. That could do it!
>
> Removing the amplifier board from the system and running without it
> was probably risky, but it seemed like a worthwhile thing to do. With
> the amp board removed, there was still no voltage from the +12 volt
> connection. It still hovered around 300mV with the set on.
> Interestingly, every now and then, a good power up was possible with
> the amp board out, and the set would come out of protection.
> Okay...where is the +12 volt supply generated?
>
> Over in the power supply section there are a few linear voltage
> regulators--two heatsinked 7812s and one freestanding 7912. One 7812
> and the 7912 are doing their jobs, but the other 7812 is cold to the
> touch and does not seem to be doing anything. (In fact, it was putting
> out 300mV when I later checked it.)
>
> Replacing the failed 7812 with an LM340 solved the problem. The set
> immediately came back to life with the amp board in place, and it
> plays. It appears, based on simple observation, that one 7812 is
> powering the coils leading up to the speaker selection/protection
> relays and the other is powering the amp board itself. What other
> loads might be powered by these regulators has not been determined.
>
> While the set is working, I don't like the temperature at which the
> new regulator is running. Within ten minutes, its heatsink is on the
> verge of being too hot to touch for more than a few seconds. There is
> evidence on the circuit board that these regulators have always run
> very hot. I've been in touch with Sherwood America, who said "the
> regulator may become too hot to touch and possibly fail". I strongly
> suspect there are bad capacitors on the amp and main boards, which
> will need to be replaced and may be stressing the regulator. Yet
> Sherwood seems to be saying that the extremely hot operation is
> *normal* here. (However, it should be said that there is something of
> a language barrier with the folks I've been communicating with.)
>
> I could install a fan above or larger heatsink on the regulator and
> I'm not above doing it if that is just the way things will be. I
> suspect that would force the regulator to operate more reliably.
>
> What I really want to know, though, is whether or not a drop-in
> replacement with more current delivering capability than the LM340 or
> 78xx series exists. I've looked halfheartedly over the years but never
> found anything. I could always build a more capable regulator board
> and hack it in there, but I don't really feel like doing that. A fan
> would be easier and faster.
>
> I'd also like to know if anyone has had an RX-5502 on their repair
> bench, and if they could comment on just how hot its regulators were
> running. Any thoughts would be very much appreciated!

Replace the burning hot 7812 with one of these:

http://www.dimensionengineering.com/datasheets/DE-SWADJ.pdf

I have no connection to the company only thinks their product is sweet.

--
Uffe Bï¿½rentsen

==============================================================================
TOPIC: FLAT, FLEXIBLE CABLE
http://groups.google.com/group/sci.electronics.repair/t/54b7b87321dcf7af?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Oct 15 2011 7:24 pm
From: justme

Hi, folks.

I have several Icom 745 radios. I need flat, flexible cable to make
up for them. The maximum conductors are 11 but I can slit more to
make 11. The spacing is .060 x .060. I have worked with a lot of
cables as I am an nnnjineer but never this type of Mylar? cable other
than plugging it in or out.

Any suggestions other than asking Icom would be appreciated.

Thank you.

== 2 of 3 ==
Date: Sat, Oct 15 2011 8:18 pm
From: Allodoxaphobia

On Sat, 15 Oct 2011 21:24:15 -0500, justme wrote:
>
> I have several Icom 745 radios. I need flat, flexible cable to make
> up for them. The maximum conductors are 11 but I can slit more to
> make 11. The spacing is .060 x .060. I have worked with a lot of
> cables as I am an nnnjineer but never this type of Mylar? cable other
> than plugging it in or out.

rec.radio.amateur.equipment

... others may have gone before you.

== 3 of 3 ==
Date: Sat, Oct 15 2011 8:25 pm
From: justme

Thanks, I will try there, too.

On 16 Oct 2011 03:18:53 GMT, Allodoxaphobia
<knock_yourself_out@example.net> wrote:

>On Sat, 15 Oct 2011 21:24:15 -0500, justme wrote:
>>
>> I have several Icom 745 radios. I need flat, flexible cable to make
>> up for them. The maximum conductors are 11 but I can slit more to
>> make 11. The spacing is .060 x .060. I have worked with a lot of
>> cables as I am an nnnjineer but never this type of Mylar? cable other
>> than plugging it in or out.
>
> rec.radio.amateur.equipment
>
> ... others may have gone before you.
>
>73
>Jonesy

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