sci.electronics.repair - 25 new messages in 10 topics - digest

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

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Today's topics:

==============================================================================
TOPIC: Repairing an expensive speaker
http://groups.google.com/group/sci.electronics.repair/t/8fc3fa133c100ac4?hl=en
==============================================================================

== 1 of 15 ==
Date: Fri, Jul 9 2010 12:57 am
From: root

Ron <ron@lunevalleyaudio.com> wrote:
>
> And that takes care of the knackered voice coil does it?
>
> Ron(UK)

Not at all, the voice coil, spider, and the cone itself
are not affected. Sorry if I missed something in the
original post.

== 2 of 15 ==
Date: Fri, Jul 9 2010 6:56 am
From: John

On Thu, 08 Jul 2010 18:56:33 -0400, Meat Plow <mhywatt@yahoo.com>
wrote:

>On Thu, 8 Jul 2010 19:15:18 +0000 (UTC), root <NoEMail@home.org>wrote:
>
>>
>>Meat Plow <mhywatt@yahoo.com> wrote:
>>>
>>> Seek out a professional reconing shop. You need some specialized tools
>>> of the trade and some talent to recone. My good friend did it for a
>>> living until he passed away recently. He would advise the same even if
>>> you didn't chose his service.
>>
>>You can buy kits for reconing speakers. It isn't a
>>hard job.
>
>Trust me, it isn't an easy fix. Just what fucking experience do you
>think I might not have had with reconing. Don't make assumptions.

This has been a very interesting and informative discussion but until
now nobody has answer my original question that was the type of glue
to use to glue the coil to the 2" tube.
Since we want the sound to come out of the cone, the connection
between the cone and the coil should be as rigid as possible and that
suggests the use of epoxy but what about heat dissipation and how to
remove a coil glued with epoxy to the tube, if some thing goes wrong?

== 3 of 15 ==
Date: Fri, Jul 9 2010 7:21 am
From: bob u

On 7/9/2010 8:56 AM, John wrote:
> On Thu, 08 Jul 2010 18:56:33 -0400, Meat Plow<mhywatt@yahoo.com>

>
> This has been a very interesting and informative discussion but until
> now nobody has answer my original question that was the type of glue
> to use to glue the coil to the 2" tube.
> Since we want the sound to come out of the cone, the connection
> between the cone and the coil should be as rigid as possible and that
> suggests the use of epoxy but what about heat dissipation and how to
> remove a coil glued with epoxy to the tube, if some thing goes wrong?

Airflex 400

bob

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

== 4 of 15 ==
Date: Fri, Jul 9 2010 7:41 am
From: zekfrivo@zekfrivolous.com (GregS)

In article <ne9e36h04d1r1cd11os3tsc6ib1oh72j4c@4ax.com>, John <Ya@you.com> wrote:
>On Thu, 08 Jul 2010 18:56:33 -0400, Meat Plow <mhywatt@yahoo.com>
>wrote:
>
>>On Thu, 8 Jul 2010 19:15:18 +0000 (UTC), root <NoEMail@home.org>wrote:
>>
>>>
>>>Meat Plow <mhywatt@yahoo.com> wrote:
>>>>
>>>> Seek out a professional reconing shop. You need some specialized tools
>>>> of the trade and some talent to recone. My good friend did it for a
>>>> living until he passed away recently. He would advise the same even if
>>>> you didn't chose his service.
>>>
>>>You can buy kits for reconing speakers. It isn't a
>>>hard job.
>>
>>Trust me, it isn't an easy fix. Just what fucking experience do you
>>think I might not have had with reconing. Don't make assumptions.
>
>This has been a very interesting and informative discussion but until
>now nobody has answer my original question that was the type of glue
>to use to glue the coil to the 2" tube.
>Since we want the sound to come out of the cone, the connection
>between the cone and the coil should be as rigid as possible and that
>suggests the use of epoxy but what about heat dissipation and how to
>remove a coil glued with epoxy to the tube, if some thing goes wrong?

If your afraid if something goes wrong, you take the advice and get
somebody to do it.

Airflex 400 is flexible, for surrounds and other repair.

The type of treatment is going to depend on what you have.
Whats the VC made out of, what kind of wire does it have.
How is it wound.
What kind of glue did they use.

By the way, I NEVER work on just one speaker.
Units must be matched for sound.

Try superglue.
Try COIL DOPE. polystyrene plastic dissolved in a solvent, toluene
You really want to use that thermal epoxy don't you.

greg

== 5 of 15 ==
Date: Fri, Jul 9 2010 8:11 am
From: zekfrivo@zekfrivolous.com (GregS)

In article <i17cc4$scl$3@usenet01.srv.cis.pitt.edu>, zekfrivo@zekfrivolous.com (GregS) wrote:
>In article <ne9e36h04d1r1cd11os3tsc6ib1oh72j4c@4ax.com>, John <Ya@you.com>
> wrote:
>>On Thu, 08 Jul 2010 18:56:33 -0400, Meat Plow <mhywatt@yahoo.com>
>>wrote:
>>
>>>On Thu, 8 Jul 2010 19:15:18 +0000 (UTC), root <NoEMail@home.org>wrote:
>>>
>>>>
>>>>Meat Plow <mhywatt@yahoo.com> wrote:
>>>>>
>>>>> Seek out a professional reconing shop. You need some specialized tools
>>>>> of the trade and some talent to recone. My good friend did it for a
>>>>> living until he passed away recently. He would advise the same even if
>>>>> you didn't chose his service.
>>>>
>>>>You can buy kits for reconing speakers. It isn't a
>>>>hard job.
>>>
>>>Trust me, it isn't an easy fix. Just what fucking experience do you
>>>think I might not have had with reconing. Don't make assumptions.
>>
>>This has been a very interesting and informative discussion but until
>>now nobody has answer my original question that was the type of glue
>>to use to glue the coil to the 2" tube.
>>Since we want the sound to come out of the cone, the connection
>>between the cone and the coil should be as rigid as possible and that
>>suggests the use of epoxy but what about heat dissipation and how to
>>remove a coil glued with epoxy to the tube, if some thing goes wrong?
>
>If your afraid if something goes wrong, you take the advice and get
>somebody to do it.
>
>Airflex 400 is flexible, for surrounds and other repair.
>
>The type of treatment is going to depend on what you have.
>Whats the VC made out of, what kind of wire does it have.
>How is it wound.
>What kind of glue did they use.
>
>By the way, I NEVER work on just one speaker.
>Units must be matched for sound.
>
>Try superglue.
>Try COIL DOPE. polystyrene plastic dissolved in a solvent, toluene
>You really want to use that thermal epoxy don't you.

The former material is going to matter. I have a feeling the
orginal "glue" was enemel, constantly rotated and baked till done.

greg

== 6 of 15 ==
Date: Fri, Jul 9 2010 8:22 am
From: "William Sommerwerck"

> This has been a very interesting and informative discussion
> but until now nobody has answer my original question that
> was the type of glue to use to glue the coil to the 2" tube.

But the question /has/ been answered -- contact the manufacturer and ask it
what the appropriate adhesive is.

You want us to give you the answer you'd like to have -- and I, for one, am
not going to do it. The manufacturer should know best.

== 7 of 15 ==
Date: Fri, Jul 9 2010 8:30 am
From: Meat Plow

On Fri, 9 Jul 2010 01:45:22 +0100, "Arfa Daily"
<arfa.daily@ntlworld.com>wrote:

>
>
>"Meat Plow" <mhywatt@yahoo.com> wrote in message
>news:3t2ats.t4n.19.4@news.alt.net...
>> On Thu, 08 Jul 2010 20:48:38 +0100, Ron
>> <ron@lunevalleyaudio.com>wrote:
>>
>>>On 08/07/2010 20:15, root wrote:
>>>> Meat Plow<mhywatt@yahoo.com> wrote:
>>>>>
>>>>> Seek out a professional reconing shop. You need some specialized tools
>>>>> of the trade and some talent to recone. My good friend did it for a
>>>>> living until he passed away recently. He would advise the same even if
>>>>> you didn't chose his service.
>>>>
>>>> You can buy kits for reconing speakers. It isn't a
>>>> hard job. You remove the flex outer rim from the
>>>> cone. Then you cut out the bulge covering the voice
>>>> coil and put shims (supplied with the kit) in to center
>>>> the cone. Then you glue new flex material around
>>>> the cone, and wait overnight. Then you remove the
>>>> shims and seal up the bulge with glue.
>>>>
>>>> Apart from the overnight wait for glue to dry, it
>>>> only took me about half an hour the first time.
>>>> With practice I might be able to get it down to
>>>> 10 minutes.
>>>
>>>And that takes care of the knackered voice coil does it?
>>>
>>>Ron(UK)
>>
>> The 10 minute recone part really bothers me. Sure with production line
>> jigs, shims, guides and people who do maybe a 100 per day that is a
>> tangible goal. But for an average Joe buying reconing parts and being
>> successful is not the average outcome. Sure there are exceptions so if
>> you want to try it on your own good luck.
>
>
>Interestingly, I was discussing exactly this issue with the owner of the
>music shop that I do a lot of work for, just this week. He rents a lot of
>biiiiigggg PA equipment out - kilowatt amps and 4 x 15 bass cabs and such.
>These get damaged by inept users all the time, apparently. I suggested that
>it must cost him a fortune in replacement speakers, but he said "Oh no - I
>just re-cone them". I asked him how long he had been doing this and he said
>years, but I had never seen this going on in his shop. Anyway, I asked him
>how long it took, and how hard a job it was, and did he have lots of
>specialist shims and feeler gauges and jigs and what have you. Nope, he
>said. He reckons it takes him but a few minutes (literally) to do the job.
>He says that the most time consuming part is making sure that all the crud
>from the burnt up voice coil, is removed from the airgap. He uses a
>combination of compressed air, and sticky tape to do this. As to centering
>the new cone's voice coil, he says that most replacement kits come with a
>set of four plastic spacer shims, but that many modern designs are
>fundamentally self - centering anyway. He reckoned that it was basically a
>piece of piss job that just needed a little care, and that much bollocks was
>talked on the subject. I might ask him to let me know next time he's got one
>to do, as I would like to watch him at work ...
>
>Arfa

I've been around when my buddy Bart reconed some pro-audio speakers.
It all comes down to people doing it the way they have learned. It's
not as easy as you think but it isn't hard either. He chose to buy
specific tools and glues and treatments not relying on kits for shims
and glues. He knew what he was doing and reconed all my speakers.
Never had a re-run because of a botched repair. Hey if you can learn
the essentials and want to give reconing a try go for it. Maybe it's
for you maybe it's not.

== 8 of 15 ==
Date: Fri, Jul 9 2010 8:33 am
From: TMI

When voice coils are wound the former which you refer to as a 2" tube,
is placed an a mandrel with an expanding collet. In better speakers,
it is "wet wound" in glue under precise tension onto the former to
create a mechanically homogeneous coil, using a precision "coil
winder" which advances the width of the wire for each turn of the
mandrel. Without the mandrel and the collet, you cannot apply the
correct tension to the wire, assuming you knew what it was.

Old cones are not good cones and become tired, particularly after an
event like you describe. New cones have a break-in period of several
months until the spider and surround stabilize at their nominal
compliance.

Tannoy speakers are high efficiency with relatively small magnets
which point to a tight gap. This is very unforgiving with respect to
egging the coil and former, extra glue from the repair, misalignment,
debris, nonlinearity of the reworked spider, surround and cone.

You do not mention centering the coil in the excursion, which is
critical for low distortion and is 90 degrees away from the shims.
Since this alignment opposes the spring action of the suspension, the
cone and spider must have no glue grooves to the former.

In short, buy the cone kits or better still, ship the drivers to allow
someone who does vintage Tannoy work to install them and preserve
those $5,000.00 speakers through restoration. A top notch shop may
also have a magnet charger to restore the specified flux density to
the gap.

Tell you friend that there are few "Vintage" cassette decks and for
what this repair is going to cost he should look for something newer.

About glue....a bit of acetone can be used (in areas other than the
coil where it may create a shorted turn) to rewet and bond glue that
has cracked. GC Radio and TV Service Cement was the old fashioned
method used by TV repair shops. Real speaker reconers use the OEM
glues.

Adding epoxy to a solvent based glue joint is a cobblers repair.

Using epoxy in place of a solvent cement is better, but still
different. While tougher, epoxy often lacks the Q of a solvent cement
joint that has aged, particularly when mixed and applied by hand which
yields entrapped air and sloppy nonuniform ratios.

These observations do not apply to modern 1KW drivers used in PA
systems and beaten to death every weekend. Your friend's solution is
perfectly valid in this application and a little DEVCON goes a long
way toward a reasonable operating cost.

Tom Maguire
TMI Engineering

== 9 of 15 ==
Date: Fri, Jul 9 2010 9:28 am
From: Ron

On 09/07/2010 16:33, TMI wrote:
> When voice coils are wound the former which you refer to as a 2" tube,
> is placed an a mandrel with an expanding collet. In better speakers,
> it is "wet wound" in glue under precise tension onto the former to
> create a mechanically homogeneous coil, using a precision "coil
> winder" which advances the width of the wire for each turn of the
> mandrel. Without the mandrel and the collet, you cannot apply the
> correct tension to the wire, assuming you knew what it was.
>
> Old cones are not good cones and become tired, particularly after an
> event like you describe. New cones have a break-in period of several
> months until the spider and surround stabilize at their nominal
> compliance.
>
> Tannoy speakers are high efficiency with relatively small magnets
> which point to a tight gap. This is very unforgiving with respect to
> egging the coil and former, extra glue from the repair, misalignment,
> debris, nonlinearity of the reworked spider, surround and cone.
>
> You do not mention centering the coil in the excursion, which is
> critical for low distortion and is 90 degrees away from the shims.
> Since this alignment opposes the spring action of the suspension, the
> cone and spider must have no glue grooves to the former.
>
> In short, buy the cone kits or better still, ship the drivers to allow
> someone who does vintage Tannoy work to install them and preserve
> those $5,000.00 speakers through restoration. A top notch shop may
> also have a magnet charger to restore the specified flux density to
> the gap.
>
> Tell you friend that there are few "Vintage" cassette decks and for
> what this repair is going to cost he should look for something newer.
>
> About glue....a bit of acetone can be used (in areas other than the
> coil where it may create a shorted turn) to rewet and bond glue that
> has cracked. GC Radio and TV Service Cement was the old fashioned
> method used by TV repair shops. Real speaker reconers use the OEM
> glues.
>
> Adding epoxy to a solvent based glue joint is a cobblers repair.
>
> Using epoxy in place of a solvent cement is better, but still
> different. While tougher, epoxy often lacks the Q of a solvent cement
> joint that has aged, particularly when mixed and applied by hand which
> yields entrapped air and sloppy nonuniform ratios.
>
> These observations do not apply to modern 1KW drivers used in PA
> systems and beaten to death every weekend. Your friend's solution is
> perfectly valid in this application and a little DEVCON goes a long
> way toward a reasonable operating cost.
>
> Tom Maguire
> TMI Engineering

Interestingly, a similar discussion has been going on over in
alt.audio.pro.live-sound, tho mainly concerned with repairing cracked
magnets.

I was surprised (after seeing a program on tv - to find out that
ferrites are magnetised _after_ assembly with the motor and basket assembly

Veejo here

http://www.youtube.com/watch?v=VN0tmyyC0ak

Ron(UK)

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== 10 of 15 ==
Date: Fri, Jul 9 2010 11:36 am
From: TMI

This is a horse of a different color.

You can't repair a cracked magnet and get the same flux in the gap
because the crack adds extra gaps. Getting the magnet to crack in the
first place usually means something horrible happened to the driver.
Buy a new one.

If you ever tried to assemble something with a charged magnet,
particularlly something with a gap you did not want to close, it would
make a lot more sense. The assembly acts to protect the charge from
being deminished by nearby magnets. It also allows you to achieve the
specified flux in the gap of the assembled speaker, where the rubber
truly meets the road.

Tom Maguire
TMI Engineering

> Interestingly, a similar discussion has been going on over in
> alt.audio.pro.live-sound, tho mainly concerned with repairing cracked
> magnets.
>
> I was surprised (after seeing a program on tv - to find out that
> ferrites are magnetised _after_ assembly with the motor and basket assembly
>
> Veejo here
>
> http://www.youtube.com/watch?v=VN0tmyyC0ak
>
> Ron(UK)
>
> --
> I am using the free version of SPAMfighter.
> We are a community of 7 million users fighting spam.
> SPAMfighter has removed 1438 of my spam emails to date.
> Get the free SPAMfighter here:http://www.spamfighter.com/len
>
> The Professional version does not have this message- Hide quoted text -
>
> - Show quoted text -

== 11 of 15 ==
Date: Fri, Jul 9 2010 12:39 pm
From: "Arfa Daily"

"Meat Plow" <mhywatt@yahoo.com> wrote in message
news:3t44sc.v8m.19.13@news.alt.net...
> On Fri, 9 Jul 2010 01:45:22 +0100, "Arfa Daily"
> <arfa.daily@ntlworld.com>wrote:
>
>>
>>
>>"Meat Plow" <mhywatt@yahoo.com> wrote in message
>>news:3t2ats.t4n.19.4@news.alt.net...
>>> On Thu, 08 Jul 2010 20:48:38 +0100, Ron
>>> <ron@lunevalleyaudio.com>wrote:
>>>
>>>>On 08/07/2010 20:15, root wrote:
>>>>> Meat Plow<mhywatt@yahoo.com> wrote:
>>>>>>
>>>>>> Seek out a professional reconing shop. You need some specialized
>>>>>> tools
>>>>>> of the trade and some talent to recone. My good friend did it for a
>>>>>> living until he passed away recently. He would advise the same even
>>>>>> if
>>>>>> you didn't chose his service.
>>>>>
>>>>> You can buy kits for reconing speakers. It isn't a
>>>>> hard job. You remove the flex outer rim from the
>>>>> cone. Then you cut out the bulge covering the voice
>>>>> coil and put shims (supplied with the kit) in to center
>>>>> the cone. Then you glue new flex material around
>>>>> the cone, and wait overnight. Then you remove the
>>>>> shims and seal up the bulge with glue.
>>>>>
>>>>> Apart from the overnight wait for glue to dry, it
>>>>> only took me about half an hour the first time.
>>>>> With practice I might be able to get it down to
>>>>> 10 minutes.
>>>>
>>>>And that takes care of the knackered voice coil does it?
>>>>
>>>>Ron(UK)
>>>
>>> The 10 minute recone part really bothers me. Sure with production line
>>> jigs, shims, guides and people who do maybe a 100 per day that is a
>>> tangible goal. But for an average Joe buying reconing parts and being
>>> successful is not the average outcome. Sure there are exceptions so if
>>> you want to try it on your own good luck.
>>
>>
>>Interestingly, I was discussing exactly this issue with the owner of the
>>music shop that I do a lot of work for, just this week. He rents a lot of
>>biiiiigggg PA equipment out - kilowatt amps and 4 x 15 bass cabs and
>>such.
>>These get damaged by inept users all the time, apparently. I suggested
>>that
>>it must cost him a fortune in replacement speakers, but he said "Oh no - I
>>just re-cone them". I asked him how long he had been doing this and he
>>said
>>years, but I had never seen this going on in his shop. Anyway, I asked him
>>how long it took, and how hard a job it was, and did he have lots of
>>specialist shims and feeler gauges and jigs and what have you. Nope, he
>>said. He reckons it takes him but a few minutes (literally) to do the job.
>>He says that the most time consuming part is making sure that all the crud
>>from the burnt up voice coil, is removed from the airgap. He uses a
>>combination of compressed air, and sticky tape to do this. As to centering
>>the new cone's voice coil, he says that most replacement kits come with a
>>set of four plastic spacer shims, but that many modern designs are
>>fundamentally self - centering anyway. He reckoned that it was basically a
>>piece of piss job that just needed a little care, and that much bollocks
>>was
>>talked on the subject. I might ask him to let me know next time he's got
>>one
>>to do, as I would like to watch him at work ...
>>
>>Arfa
>
> I've been around when my buddy Bart reconed some pro-audio speakers.
> It all comes down to people doing it the way they have learned. It's
> not as easy as you think but it isn't hard either. He chose to buy
> specific tools and glues and treatments not relying on kits for shims
> and glues. He knew what he was doing and reconed all my speakers.
> Never had a re-run because of a botched repair. Hey if you can learn
> the essentials and want to give reconing a try go for it. Maybe it's
> for you maybe it's not.

I don't reckon I've got the patience, Meat. I had always thought that it was
quite a tricky and skilled job, so I was just interested to have a watch
next time Dunc does one, as he reckoned it was so straightforward !

Arfa

== 12 of 15 ==
Date: Fri, Jul 9 2010 1:08 pm
From: Ron

On 09/07/2010 19:36, TMI wrote:
> This is a horse of a different color.
>
> You can't repair a cracked magnet and get the same flux in the gap
> because the crack adds extra gaps. Getting the magnet to crack in the
> first place usually means something horrible happened to the driver.
> Buy a new one.

Cracked ferrites _are_ repaired but only as a last resort in cases where
there's no alternative. We've been through this recently on another n/g.
It's not recommended, but it can be done.

According to a large professional loudspeaker repair company I contacted
on the subject, de-magnetising and remagnetising also is to be avoided
as it loses flux.

Ron(UK)
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== 13 of 15 ==
Date: Fri, Jul 9 2010 2:15 pm
From: John

On Fri, 9 Jul 2010 08:22:27 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>> This has been a very interesting and informative discussion
>> but until now nobody has answer my original question that
>> was the type of glue to use to glue the coil to the 2" tube.
>
>But the question /has/ been answered -- contact the manufacturer and ask it
>what the appropriate adhesive is.
>
>You want us to give you the answer you'd like to have -- and I, for one, am
>not going to do it. The manufacturer should know best.
>

That was the first thing I did and the answer from Tannoy was:

"We don't have the kit but you may get it from company x. Then send
the complete assembly to the closest Tannoy service center (200 miles
from my residence) and we will do the reconing.
We don't recommend changing the coil."

The installation of the kit is easy. It is self center and it doesn't
have play adjustments.

In order to do a god job, I should order 2 cone kits from England but
the total cost including transportation, duty an taxes will be more
than $1k.

The speaker with less damage has about 6 turns dislocated as a group
from the rest of the coil that looks solid.
I am going to read again your recommendations about the glue, paint
the 2" tube with that glue and slide the 6 turns group into their
previous position.

If this works I may try to rewind the other coil "fat chance"

Then I may order one or two kits from England and do the reconing
myself.

Thanks for all your help.

John

== 14 of 15 ==
Date: Fri, Jul 9 2010 2:36 pm
From: Cydrome Leader

Ron <ron@lunevalleyaudio.com> wrote:
> On 09/07/2010 16:33, TMI wrote:
>> When voice coils are wound the former which you refer to as a 2" tube,
>> is placed an a mandrel with an expanding collet. In better speakers,
>> it is "wet wound" in glue under precise tension onto the former to
>> create a mechanically homogeneous coil, using a precision "coil
>> winder" which advances the width of the wire for each turn of the
>> mandrel. Without the mandrel and the collet, you cannot apply the
>> correct tension to the wire, assuming you knew what it was.
>>
>> Old cones are not good cones and become tired, particularly after an
>> event like you describe. New cones have a break-in period of several
>> months until the spider and surround stabilize at their nominal
>> compliance.
>>
>> Tannoy speakers are high efficiency with relatively small magnets
>> which point to a tight gap. This is very unforgiving with respect to
>> egging the coil and former, extra glue from the repair, misalignment,
>> debris, nonlinearity of the reworked spider, surround and cone.
>>
>> You do not mention centering the coil in the excursion, which is
>> critical for low distortion and is 90 degrees away from the shims.
>> Since this alignment opposes the spring action of the suspension, the
>> cone and spider must have no glue grooves to the former.
>>
>> In short, buy the cone kits or better still, ship the drivers to allow
>> someone who does vintage Tannoy work to install them and preserve
>> those $5,000.00 speakers through restoration. A top notch shop may
>> also have a magnet charger to restore the specified flux density to
>> the gap.
>>
>> Tell you friend that there are few "Vintage" cassette decks and for
>> what this repair is going to cost he should look for something newer.
>>
>> About glue....a bit of acetone can be used (in areas other than the
>> coil where it may create a shorted turn) to rewet and bond glue that
>> has cracked. GC Radio and TV Service Cement was the old fashioned
>> method used by TV repair shops. Real speaker reconers use the OEM
>> glues.
>>
>> Adding epoxy to a solvent based glue joint is a cobblers repair.
>>
>> Using epoxy in place of a solvent cement is better, but still
>> different. While tougher, epoxy often lacks the Q of a solvent cement
>> joint that has aged, particularly when mixed and applied by hand which
>> yields entrapped air and sloppy nonuniform ratios.
>>
>> These observations do not apply to modern 1KW drivers used in PA
>> systems and beaten to death every weekend. Your friend's solution is
>> perfectly valid in this application and a little DEVCON goes a long
>> way toward a reasonable operating cost.
>>
>> Tom Maguire
>> TMI Engineering
>
>
> Interestingly, a similar discussion has been going on over in
> alt.audio.pro.live-sound, tho mainly concerned with repairing cracked
> magnets.
>
> I was surprised (after seeing a program on tv - to find out that
> ferrites are magnetised _after_ assembly with the motor and basket assembly
>
> Veejo here
>
> http://www.youtube.com/watch?v=VN0tmyyC0ak

hahaha. Skip to 2:10

they magnetize the ferrite with the operator panel from a reel to reel
tape drive or some washing machine sized hard drive, and by pushing the
Fault button.

== 15 of 15 ==
Date: Fri, Jul 9 2010 3:01 pm
From: Jeffrey D Angus

Cydrome Leader wrote:
>> http://www.youtube.com/watch?v=VN0tmyyC0ak
>
> hahaha. Skip to 2:10
>
> they magnetize the ferrite with the operator panel from a reel to reel
> tape drive or some washing machine sized hard drive, and by pushing the
> Fault button.

Yeah, I thought the button legends were a bit odd.
Equally funny is watching the whole thing jump in the fixture.

Jeff

--
"Egotism is the anesthetic that dulls the pain of stupidity."
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com

==============================================================================
TOPIC: Chanel goggle (http://www.brandtrade99.com free shipping)
http://groups.google.com/group/sci.electronics.repair/t/248d15f99be67229?hl=en
==============================================================================

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TOPIC: Electric fence operation problem
http://groups.google.com/group/sci.electronics.repair/t/eef28366a8aa3bbf?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jul 9 2010 1:12 am
From: Franc Zabkar

On Fri, 9 Jul 2010 08:45:56 +0100, "N_Cook" <diverse@tcp.co.uk> put
finger to keyboard and composed:

>There is a chain of 3.3M resistors for feedback , I suspect it would change
>the 1.5KHz multivibrator rather than the 300KHz one. There is also the 1 to
>2 second repetition cycling, perhaps 3 multivibrator package, also
>unreadable marking

I would expect that the multivibrator would have an internal reference
voltage which it would compare against the voltage on the resistor at
the bottom end of the potential divider. The IC's reference voltage
may appear on one of its pins.

I would locate where the divider feeds into the IC, and determine the
values of all the resistances in the chain. Then measure the voltages
on the pins on either side of the feedback pin. If you can supply this
information, then perhaps it will help ascertain the capacitor
voltage.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

==============================================================================
TOPIC: CRT: Brief contrast/brightness prob at start-up.
http://groups.google.com/group/sci.electronics.repair/t/cdf227264ff94f95?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jul 9 2010 1:43 am
From: "Arfa Daily"

"Meatman" <KevinLee33@comcast.net> wrote in message
news:6f199bd8-ac89-41ee-a6e0-6aae02e397cd@y11g2000yqm.googlegroups.com...
> 32" RCA Entertainment Series CRT. Had popping noise w/ no pic or
> sound. Replaced HOT and FBT. Now A-OK except: At start-up, every start-
> up, contrast/brightness is way low/very dark picture. After 3-5 secs
> it corrects and is normal. I even let it run for 30 hrs straight to
> see if it would freak-out in other ways. It didn't. Problem is quite
> sufferable, but I'd like to chase it down. Ideas? Thanks again!

Wrongly set 'screen' control on your new FBT ? Taking a while for the beam
limiter to assess what's going on and correct for it ? If original FBT was
faulty, beam limiter sense resistor in ground return gone high ?

Arfa

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http://groups.google.com/group/sci.electronics.repair/t/45398294d79f87d6?hl=en
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TOPIC: I WISH SOMEONE WOULD HAVE SHOWED ME THIS SOONER! LOVE IT!
http://groups.google.com/group/sci.electronics.repair/t/9e517993b60c10af?hl=en
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== 1 of 1 ==
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TOPIC: PLEASE HELP!
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TOPIC: Polaroid TLX-04011C vertical stripe
http://groups.google.com/group/sci.electronics.repair/t/4c8b4302f2fee97b?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jul 9 2010 11:47 am
From: PlainBill47@yahoo.com

On Wed, 7 Jul 2010 05:38:55 -0700 (PDT), klem kedidelhopper
<captainvideo462009@gmail.com> wrote:

>On Jul 6, 2:28 pm, PlainBil...@yahoo.com wrote:
>> On Tue, 6 Jul 2010 07:12:43 -0700 (PDT), klem kedidelhopper
>>
>> <captainvideo462...@gmail.com> wrote:
>> >This set has a dim vertical bar about 4 inches wide just to the right
>> >of center screen. There is a normal full color picture otherwise but
>> >this "bar" is a bit dimmer than the rest of the screen, and so its
>> >noticible. The strange thing is though depending upon the scene
>> >sometimes you don't notice it at all and at other times it seems quite
>> >prominent. At times you can notice smears of red going through this
>> >area as well. The customer says he did a search on this thing and
>> >seems to think it needs a "capacitor". But then sometimes they tell me
>> >its the switch when it won't turn on too. I looked but found nothing
>> >that really seems to pertain to this problem exectly.
>> >Does anyone have any experience with this problem on this set? Thanks,
>> >Lenny
>>
>> Is this a sharply deliniated bar, indicating a problem with columns of
>> pixels, or do the edges gradually merge into the 'good' area.
>> A sharp edged column would indicate a problem either with a column
>> driver in the LCD panel itself (not repairable), or the t-con board
>> (usually replaceable).
>>
>> A dimmer column with no sharp edges could indicate a backlight
>> problem.
>>
>> As far as the customer's suggestion, while it is unlikely, this
>> wouldn't be the first time some very strange symptoms resulted from a
>> marginal capacitor.
>>
>> PlainBill
>
>The edges are sharply defined however the "column" is slightly
>somewhat dimmer than the rest of the picture. That's what makes it
>noticeable I guess. How do you rule out /in a t con board? I did try
>cleaning the cable but it made no difference.Thanks, Lenny
The only way to evaluate the t-con board is by replacement with a
known good one. Because of the way the drivers are arranged, this is
most likely due to a bad driver IC.

PlainBill

==============================================================================
TOPIC: How to dissolve clear plastic coat from circuit boards?
http://groups.google.com/group/sci.electronics.repair/t/3589eaf245b53d57?hl=en
==============================================================================

== 1 of 2 ==
Date: Fri, Jul 9 2010 2:20 pm
From: "Robbie Hatley"

"Dave Platt" wrote:

> Robbie Hatley wrote:
>
> > Greetings, group. I've got a sticky issue here. I'm repairing a number
> > of circuit
> > boards from a manufacturer who coats their boards after assembly with some
> > sort of plastic clear coat. (Polyurethane, maybe? Indoors it's clear and
> > colorless, but outdoors under skylight, it glows a pale blue.) It makes probing
> > and soldering/unsoldering quite difficult. What's the best way to remove it?
>
> Google "conformal coating stripper".

Ah, so that's what that coating is called. I was looking for "plastic clear coat".

> MG chemicals makes one ...

Brush-on gel. Don't think that's what I need.

> Miller-Stephenson ... D0319B ...

Yep, I'm going to look into that, see if I can get a quart. (Have to order
local, because it can't be shipped any way other than ground.)

Thanks for the tip on that!

> ... The pale-blue glow you observed is probably a UV-fluorescent tracer dye...

Confirmed. Coworker put a UV light on it, and it glows crazily. (The cuticles
of all the fingers of my left hand also glow extremely brightly under UV;
seems I now have a poisonous muck of plastic resins, toxic solvents, and
radioactive isotopes embedded under my fingernails. Great. Sigh. I'll have
to remember to wear gloves before cleaning these boards from now on.)

--
Cheers,
RH
lonewolf [[at]] well [[dot]] com

== 2 of 2 ==
Date: Fri, Jul 9 2010 3:24 pm
From: "William Sommerwerck"

> Confirmed. Coworker put a UV light on it, and it glows crazily. (The
> cuticles of all the fingers of my left hand also glow extremely brightly
> under UV; seems I now have a poisonous muck of plastic resins,
> toxic solvents, and radioactive isotopes embedded under my
> fingernails. Great. Sigh.)

Actually, you're mutating into a scorpion.

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