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

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Today's topics:

* Luxmeter problem - 3 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/3131ff981cfbd416?hl=en
* Black Glue Peril - 16 messages, 8 authors
http://groups.google.com/group/sci.electronics.repair/t/e2b7af1ebdef2435?hl=en
* What to do when a key stops working on a Laptop keyboard? - 1 messages, 1
author
http://groups.google.com/group/sci.electronics.repair/t/bbd9adad1ab1364d?hl=en
* alliance antenna rotor - 3 messages, 3 authors
http://groups.google.com/group/sci.electronics.repair/t/60e644314adaefab?hl=en
* IC Identification Help (SMD Marking 651+, or maybe G51+), SOT-23-6 - 1
messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/03b5c5812be29ee3?hl=en
* Converting a 200W discharge lamp video projector to LED - 1 messages, 1
author
http://groups.google.com/group/sci.electronics.repair/t/c84c8e901a969276?hl=en
* Dual Channel Software Oscilloscope Ver 2.0 - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/fccc843f2ff99948?hl=en

==============================================================================
TOPIC: Luxmeter problem
http://groups.google.com/group/sci.electronics.repair/t/3131ff981cfbd416?hl=en
==============================================================================

== 1 of 3 ==
Date: Thurs, Oct 3 2013 9:49 am
From: ggherold@gmail.com


On Wednesday, October 2, 2013 1:16:14 PM UTC-4, N_Cook wrote:
> the BPW21 datasheet shows log-log plot of short circuit current v lux
>
> over 6 decades as linear, so something about short circuit compared with
>
> actual use?

I assume it's a photodiode. Then short circiut current is very linear. You'd have to share the circuit. But if they just use a simple resistor across the diode to convert I to V, then it becomes non-linear as the diode becomes forward biased and some of the current goes back though the diode and not the resistor.

George H.




== 2 of 3 ==
Date: Thurs, Oct 3 2013 10:44 am
From: N_Cook


On 03/10/2013 17:49, ggherold@gmail.com wrote:
> On Wednesday, October 2, 2013 1:16:14 PM UTC-4, N_Cook wrote:
>> the BPW21 datasheet shows log-log plot of short circuit current v lux
>>
>> over 6 decades as linear, so something about short circuit compared with
>>
>> actual use?
>
> I assume it's a photodiode. Then short circiut current is very linear. You'd have to share the circuit. But if they just use a simple resistor across the diode to convert I to V, then it becomes non-linear as the diode becomes forward biased and some of the current goes back though the diode and not the resistor.
>
> George H.
>

Sounds plausible.
No known schematic but I'll dig out the data for the main chip and work
out what applies to it and lux measurement, which should show which pair
of presets and which is zero and which is range.




== 3 of 3 ==
Date: Thurs, Oct 3 2013 11:58 pm
From: N_Cook


The photodiode is in series with 18K and one end of those 2 is connected
to an opamp input and the other end to another opamp input. So cannot be
fully linear. I.m reasonably confident which preset relates to which
function.
Overal zero and overall scaling, then one for scaling the temperature
function and one for the lux. The extra CMOS for OR driving the always
on 0 digit and the switching function and maybe auto-off function. As it
stands with zero lux it reads -80 lux so something obviously adrift.
Adjusting light levels up from zero , then from -20 to probably +20 it
auto "zeros" to 0. The temperature scale is easy to check calibration,
which leaves the lux scale.
Looks as though the nearest i will get to a reference light source is
taking the average of a number of 60watt mains tungsten lamps, but then
www sources say that is betwwen 700 lumens to 900 lumens, mostly about
840 to 870, and monitor 1 metre away. Accept that a reading of 20,000 is
nearer 100,000 lux and produce a corelation chart via some unknown but
constant value of bright source and 1,2,3, and 4 stop (1/2 to 1/16)
neutral density filters over the sensor .





==============================================================================
TOPIC: Black Glue Peril
http://groups.google.com/group/sci.electronics.repair/t/e2b7af1ebdef2435?hl=en
==============================================================================

== 1 of 16 ==
Date: Thurs, Oct 3 2013 4:33 pm
From: "Phil Allison"


** Hi to all,

the dreaded " Yellow Glue" problem has been mentioned here a few times.

I have exactly the same problem, but the glue is now black instead - with a
KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
liberally covered in the stuff, more on the amplifier and PSU one.

Symptoms in my example were loud crackling and low volume - which
recovered when I wound the AC back to 160V !!

Seems you have to get every bit of it off to effect repair. Along the way
you will see corroded leads and PCB link wires - there is a 2.2kohm next
to the filter caps that is buried in the glue and needs replacing.

This is worse than the Yellow Glue problem as it becomes conductive in areas
that have no heat.

Could the black colouring be carbon ??


... Phil








== 2 of 16 ==
Date: Fri, Oct 4 2013 3:50 am
From: "Gareth Magennis"



"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:bb6d6fFhbqrU1@mid.individual.net...
> ** Hi to all,
>
> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>
> I have exactly the same problem, but the glue is now black instead - with
> a KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
> liberally covered in the stuff, more on the amplifier and PSU one.
>
> Symptoms in my example were loud crackling and low volume - which
> recovered when I wound the AC back to 160V !!
>
> Seems you have to get every bit of it off to effect repair. Along the way
> you will see corroded leads and PCB link wires - there is a 2.2kohm next
> to the filter caps that is buried in the glue and needs replacing.
>
> This is worse than the Yellow Glue problem as it becomes conductive in
> areas that have no heat.
>
> Could the black colouring be carbon ??
>
>
> ... Phil
>
>


I've been seeing this black stuff for a while now, on KRK, Alesis and Tannoy
powered monitors, but curiously not other types of equipment.
Perhaps they are all made in the same factory.

Could well contain carbon.
http://www.specialchem4coatings.com/tc/color-handbook/?id=black

This stuff get it off quite nicely.
http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160

(Arfa Daly recommended this product a while ago on this forum, I've tried
it, and it does work well)



Cheers,

Gareth.






== 3 of 16 ==
Date: Fri, Oct 4 2013 4:01 am
From: "Phil Allison"



"Gareth Magennis"
> "Phil Allison"
>
>> ** Hi to all,
>>
>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>
>> I have exactly the same problem, but the glue is now black instead -
>> with a KRK 'Rokit 5" powered monitor - from China of course. Both PCBs
>> are liberally covered in the stuff, more on the amplifier and PSU one.
>>
>> Symptoms in my example were loud crackling and low volume - which
>> recovered when I wound the AC back to 160V !!
>>
>> Seems you have to get every bit of it off to effect repair. Along the way
>> you will see corroded leads and PCB link wires - there is a 2.2kohm
>> next to the filter caps that is buried in the glue and needs replacing.
>>
>> This is worse than the Yellow Glue problem as it becomes conductive in
>> areas that have no heat.
>>
>> Could the black colouring be carbon ??
>>
>
>
> I've been seeing this black stuff for a while now, on KRK, Alesis and
> Tannoy powered monitors, but curiously not other types of equipment.
> Perhaps they are all made in the same factory.

** Very likely.


> Could well contain carbon.
> http://www.specialchem4coatings.com/tc/color-handbook/?id=black


** Wot a bad idea.

>
> This stuff get it off quite nicely.
> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>

** Does it simply dissolve the horrible stuff ?

What the KRKs use goes rock hard and has to be chipped of with *ridiculous*
amounts of force.

I have been using a jeweller's screwdriver, hit repeatedly with a back end
of a small shifting spanner.

Stone mason's stuff.



... Phil








== 4 of 16 ==
Date: Fri, Oct 4 2013 4:30 am
From: "Gareth Magennis"



"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:bb7lgpFp1edU1@mid.individual.net...
>
> "Gareth Magennis"
>> "Phil Allison"
>>
>>> ** Hi to all,
>>>
>>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>>
>>> I have exactly the same problem, but the glue is now black instead -
>>> with a KRK 'Rokit 5" powered monitor - from China of course. Both PCBs
>>> are liberally covered in the stuff, more on the amplifier and PSU one.
>>>
>>> Symptoms in my example were loud crackling and low volume - which
>>> recovered when I wound the AC back to 160V !!
>>>
>>> Seems you have to get every bit of it off to effect repair. Along the
>>> way you will see corroded leads and PCB link wires - there is a
>>> 2.2kohm next to the filter caps that is buried in the glue and needs
>>> replacing.
>>>
>>> This is worse than the Yellow Glue problem as it becomes conductive in
>>> areas that have no heat.
>>>
>>> Could the black colouring be carbon ??
>>>
>>
>>
>> I've been seeing this black stuff for a while now, on KRK, Alesis and
>> Tannoy powered monitors, but curiously not other types of equipment.
>> Perhaps they are all made in the same factory.
>
> ** Very likely.
>
>
>> Could well contain carbon.
>> http://www.specialchem4coatings.com/tc/color-handbook/?id=black
>
>
> ** Wot a bad idea.
>
>>
>> This stuff get it off quite nicely.
>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>
>
> ** Does it simply dissolve the horrible stuff ?
>
> What the KRKs use goes rock hard and has to be chipped of with
> *ridiculous* amounts of force.
>
> I have been using a jeweller's screwdriver, hit repeatedly with a back end
> of a small shifting spanner.
>
> Stone mason's stuff.
>
>
>
> ... Phil
>


That sounds more like an epoxy, maybe not the same stuff?
But why would it need to be black anyway? Just makes it more expensive than
uncloloured adhesive.

The flux cleaner I think just softens it, so it doesn't adhere as strongly
to the PCB. Arfa might be able to confirm or deny this.



Incidentally, I recently made my own black speaker glue (for fixing dust
caps) using Evostick and laser printer toner. Works a treat, and a damn
sight cheaper than this tiny tube of what is probably the same stuff.

http://www.saveltd.co.uk/jbl-professional-moyen-rs-3087-speaker-driver-cement-glue-4125-p.asp




Gareth.






== 5 of 16 ==
Date: Fri, Oct 4 2013 5:14 am
From: "Phil Allison"



"Gareth Magennis"
> "Phil Allison"
>>
>>> I've been seeing this black stuff for a while now, on KRK, Alesis and
>>> Tannoy powered monitors, but curiously not other types of equipment.
>>> Perhaps they are all made in the same factory.
>>
>> ** Very likely.
>
>>>
>>> This stuff get it off quite nicely.
>>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>>
>>
>> ** Does it simply dissolve the horrible stuff ?
>>
>> What the KRKs use goes rock hard and has to be chipped of with
>> *ridiculous* amounts of force.
>>
>> I have been using a jeweller's screwdriver, hit repeatedly with a back
>> end of a small shifting spanner.
>>
>> Stone mason's stuff.
>>
>
> That sounds more like an epoxy, maybe not the same stuff?

** It's the same horrible stuff - just black.

Time and a bit of heat turns it into rock.


> But why would it need to be black anyway?


** IEC inlets, rocker switches, XLRs and metal back panels are commonly
black.

So it matches, when used to achieve an air seal around them, like in this
case.



... Phil









== 6 of 16 ==
Date: Fri, Oct 4 2013 5:30 am
From: N_Cook


On 04/10/2013 12:30, Gareth Magennis wrote:
> "Phil Allison" <phil_a@tpg.com.au> wrote in message
> news:bb7lgpFp1edU1@mid.individual.net...
>>
>> "Gareth Magennis"
>>> "Phil Allison"
>>>
>>>> ** Hi to all,
>>>>
>>>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>>>
>>>> I have exactly the same problem, but the glue is now black instead -
>>>> with a KRK 'Rokit 5" powered monitor - from China of course. Both PCBs
>>>> are liberally covered in the stuff, more on the amplifier and PSU one.
>>>>
>>>> Symptoms in my example were loud crackling and low volume - which
>>>> recovered when I wound the AC back to 160V !!
>>>>
>>>> Seems you have to get every bit of it off to effect repair. Along the
>>>> way you will see corroded leads and PCB link wires - there is a
>>>> 2.2kohm next to the filter caps that is buried in the glue and needs
>>>> replacing.
>>>>
>>>> This is worse than the Yellow Glue problem as it becomes conductive in
>>>> areas that have no heat.
>>>>
>>>> Could the black colouring be carbon ??
>>>>
>>>
>>>
>>> I've been seeing this black stuff for a while now, on KRK, Alesis and
>>> Tannoy powered monitors, but curiously not other types of equipment.
>>> Perhaps they are all made in the same factory.
>>
>> ** Very likely.
>>
>>
>>> Could well contain carbon.
>>> http://www.specialchem4coatings.com/tc/color-handbook/?id=black
>>
>>
>> ** Wot a bad idea.
>>
>>>
>>> This stuff get it off quite nicely.
>>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>>
>>
>> ** Does it simply dissolve the horrible stuff ?
>>
>> What the KRKs use goes rock hard and has to be chipped of with
>> *ridiculous* amounts of force.
>>
>> I have been using a jeweller's screwdriver, hit repeatedly with a back end
>> of a small shifting spanner.
>>
>> Stone mason's stuff.
>>
>>
>>
>> ... Phil
>>
>
>
> That sounds more like an epoxy, maybe not the same stuff?
> But why would it need to be black anyway? Just makes it more expensive than
> uncloloured adhesive.
>
> The flux cleaner I think just softens it, so it doesn't adhere as strongly
> to the PCB. Arfa might be able to confirm or deny this.
>
>
>
> Incidentally, I recently made my own black speaker glue (for fixing dust
> caps) using Evostick and laser printer toner. Works a treat, and a damn
> sight cheaper than this tiny tube of what is probably the same stuff.
>
> http://www.saveltd.co.uk/jbl-professional-moyen-rs-3087-speaker-driver-cement-glue-4125-p.asp
>
>
>
>
> Gareth.
>
>

So that makes it 3 different types that cause such problems.
The yellow glue stuff
The white softish conformal coating material that breaks down leaving a
distinctive oily film, plus corrossion/conduction problems
This black stuff now
Does no manufacturer do accelerated aging of these sorts of materials
before selling them




== 7 of 16 ==
Date: Fri, Oct 4 2013 8:04 am
From: "Gareth Magennis"


> Could well contain carbon.
> http://www.specialchem4coatings.com/tc/color-handbook/?id=black
>



From that site:

Flocculation
Following dispersion small particles of carbon black have a tendency to
flocculate. To minimize this tendency it is necessary to take utmost care
when diluting paints. Only small calculated additions should be made with
thorough homogenization between additions



So it could be that over time, whatever is used as a pigment "flocculates"
and forms solid flakes or a layer of conductivity on the PCB.

(Being as the pigment particles are not dissolved in a medium as a solution,
but are merely mixed with it)



Gareth.






== 8 of 16 ==
Date: Fri, Oct 4 2013 8:08 am
From: dave


On 10/03/2013 04:33 PM, Phil Allison wrote:
> ** Hi to all,
>
> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>
> I have exactly the same problem, but the glue is now black instead - with a
> KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
> liberally covered in the stuff, more on the amplifier and PSU one.
>
> Symptoms in my example were loud crackling and low volume - which
> recovered when I wound the AC back to 160V !!
>
> Seems you have to get every bit of it off to effect repair. Along the way
> you will see corroded leads and PCB link wires - there is a 2.2kohm next
> to the filter caps that is buried in the glue and needs replacing.
>
> This is worse than the Yellow Glue problem as it becomes conductive in areas
> that have no heat.
>
> Could the black colouring be carbon ??
>
>
> ... Phil
>
>

http://www.krksys.com/krk-history.html




== 9 of 16 ==
Date: Fri, Oct 4 2013 9:42 am
From: Jeff Liebermann


On Fri, 4 Oct 2013 16:04:40 +0100, "Gareth Magennis"
<sound.service@btconnect.com> wrote:

>> Could well contain carbon.
>> http://www.specialchem4coatings.com/tc/color-handbook/?id=black

>From that site:
>
>Flocculation
>Following dispersion small particles of carbon black have a tendency to
>flocculate. To minimize this tendency it is necessary to take utmost care
>when diluting paints. Only small calculated additions should be made with
>thorough homogenization between additions
>
>So it could be that over time, whatever is used as a pigment "flocculates"
>and forms solid flakes or a layer of conductivity on the PCB.
>
>(Being as the pigment particles are not dissolved in a medium as a solution,
>but are merely mixed with it)
>
>Gareth.

Ouch. That could be serious. If the conductive carbon particles
remain suspended in solution, the goo will not be conductive because
the space between the particles is filled with the non-conductive base
glue. However, if the carbon particles are heavier than the glue,
they might precipitate out of the colloidal solution, and settle to
the bottom of the glue joint. The carbon particles might then overlap
each other, producing a conductive layer. If the carbon particles are
lighter than the glue, they could float to the surface and form a
conductive layer on the surface. Much depends on how the goo was
mixed and applied. If it hardens quickly, I don't think there will be
a problem. If it hardens very slowly, expect trouble. If it was
diluted with solvent, it probably produce conductive clumps of carbon.


--
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




== 10 of 16 ==
Date: Fri, Oct 4 2013 10:39 am
From: "Gareth Magennis"




"Jeff Liebermann" wrote in message
news:2sqt491eg4a66sv7ce7c0o8cao04b77k1c@4ax.com...

On Fri, 4 Oct 2013 16:04:40 +0100, "Gareth Magennis"
<sound.service@btconnect.com> wrote:

>> Could well contain carbon.
>> http://www.specialchem4coatings.com/tc/color-handbook/?id=black

>From that site:
>
>Flocculation
>Following dispersion small particles of carbon black have a tendency to
>flocculate. To minimize this tendency it is necessary to take utmost care
>when diluting paints. Only small calculated additions should be made with
>thorough homogenization between additions
>
>So it could be that over time, whatever is used as a pigment "flocculates"
>and forms solid flakes or a layer of conductivity on the PCB.
>
>(Being as the pigment particles are not dissolved in a medium as a
>solution,
>but are merely mixed with it)
>
>Gareth.

Ouch. That could be serious. If the conductive carbon particles
remain suspended in solution, the goo will not be conductive because
the space between the particles is filled with the non-conductive base
glue. However, if the carbon particles are heavier than the glue,
they might precipitate out of the colloidal solution, and settle to
the bottom of the glue joint. The carbon particles might then overlap
each other, producing a conductive layer. If the carbon particles are
lighter than the glue, they could float to the surface and form a
conductive layer on the surface. Much depends on how the goo was
mixed and applied. If it hardens quickly, I don't think there will be
a problem. If it hardens very slowly, expect trouble. If it was
diluted with solvent, it probably produce conductive clumps of carbon.





There may be other factors involved.
This adhesive is typically found in powered speakers, which can undergo
quite large temperature change cycles. This could regularly soften the
glue, which might in turn cause cyclic migration or clumping of any free
conductive particles therein.

But I'm not an adhesive expert, this is all just an interesting guess.



Gareth.





== 11 of 16 ==
Date: Fri, Oct 4 2013 6:46 pm
From: "Arfa Daily"




>> This stuff get it off quite nicely.
>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>
>
> ** Does it simply dissolve the horrible stuff ?


No. It 'softens' it which then makes it become sort of 'plastic' so that it
can be peeled off the board without taking all the little surface mount
components with it


>
> What the KRKs use goes rock hard and has to be chipped of with
> *ridiculous* amounts of force.
>
> I have been using a jeweller's screwdriver, hit repeatedly with a back end
> of a small shifting spanner.


This is the sort of thing that I was doing before, but one day I got so fed
up of having to use such force that I started trying all the liquid
chemicals that I had, just in case. The Servisol 160 is my defluxer of
choice, and I have used it for many years. I sprayed some on the glue, and
left it for 5 minutes, and when I tried again to shift the stuff, it had
ceased being hard and I was able to peel it with a blunt scalpel. Make no
mistake, it still doesn't come off easily, but much easier than when it is
hard before treatment. Whether it would have the same effect on your black
stuff, though ... ??

Arfa


>
> Stone mason's stuff.
>
>
>
> ... Phil
>
>
>
>
>




== 12 of 16 ==
Date: Fri, Oct 4 2013 8:09 pm
From: "Phil Allison"



"Arfa Daily"
>
>>> This stuff get it off quite nicely.
>>> http://uk.farnell.com/servisol/100019000/flux-remover-160-200ml/dp/3821470?Ntt=de-flux+160
>>>
>>
>> ** Does it simply dissolve the horrible stuff ?
>
>
> No. It 'softens' it which then makes it become sort of 'plastic' so that
> it can be peeled off the board without taking all the little surface mount
> components with it
>
>
>>
>> What the KRKs use goes rock hard and has to be chipped of with
>> *ridiculous* amounts of force.
>>
>> I have been using a jeweller's screwdriver, hit repeatedly with a back
>> end of a small shifting spanner.
>
>
> This is the sort of thing that I was doing before, but one day I got so
> fed up of having to use such force that I started trying all the liquid
> chemicals that I had, just in case. The Servisol 160 is my defluxer of
> choice, and I have used it for many years. I sprayed some on the glue, and
> left it for 5 minutes, and when I tried again to shift the stuff, it had
> ceased being hard and I was able to peel it with a blunt scalpel. Make no
> mistake, it still doesn't come off easily, but much easier than when it is
> hard before treatment. Whether it would have the same effect on your black
> stuff, though ... ??


** Servisol 160 is mixture of a few solvents including "naphtha" the magic
ingredient in WD-40.

http://www.crcind.com/wwwcrc/msds/UK20046-23.htm

It is also highly flammable and toxic - so it must do the job ....



... Phil













== 13 of 16 ==
Date: Sat, Oct 5 2013 4:21 am
From: "Phil Allison"



"dave"
>
> Phil Allison wrote:
>
>> ** Hi to all,
>>
>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>
>> I have exactly the same problem, but the glue is now black instead -
>> with a
>> KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
>> liberally covered in the stuff, more on the amplifier and PSU one.
>>
>> Symptoms in my example were loud crackling and low volume - which
>> recovered when I wound the AC back to 160V !!
>>
>> Seems you have to get every bit of it off to effect repair. Along the way
>> you will see corroded leads and PCB link wires - there is a 2.2kohm
>> next
>> to the filter caps that is buried in the glue and needs replacing.
>>
>> This is worse than the Yellow Glue problem as it becomes conductive in
>> areas
>> that have no heat.
>>
>> Could the black colouring be carbon ??
>
>
> http://www.krksys.com/krk-history.html


** Ok, Dave, I do see the link.

Is there a particular reason you posted that to me right now ?

Juts what do you think you are doing - Dave ??




... Phil








== 14 of 16 ==
Date: Sat, Oct 5 2013 5:17 am
From: dave


On 10/05/2013 04:21 AM, Phil Allison wrote:
> "dave"
>>
>> Phil Allison wrote:
>>
>>> ** Hi to all,
>>>
>>> the dreaded " Yellow Glue" problem has been mentioned here a few times.
>>>
>>> I have exactly the same problem, but the glue is now black instead -
>>> with a
>>> KRK 'Rokit 5" powered monitor - from China of course. Both PCBs are
>>> liberally covered in the stuff, more on the amplifier and PSU one.
>>>
>>> Symptoms in my example were loud crackling and low volume - which
>>> recovered when I wound the AC back to 160V !!
>>>
>>> Seems you have to get every bit of it off to effect repair. Along the way
>>> you will see corroded leads and PCB link wires - there is a 2.2kohm
>>> next
>>> to the filter caps that is buried in the glue and needs replacing.
>>>
>>> This is worse than the Yellow Glue problem as it becomes conductive in
>>> areas
>>> that have no heat.
>>>
>>> Could the black colouring be carbon ??
>>
>>
>> http://www.krksys.com/krk-history.html
>
>
> ** Ok, Dave, I do see the link.
>
> Is there a particular reason you posted that to me right now ?
>
> Juts what do you think you are doing - Dave ??
>
>
>
>
> ... Phil
>

Pointing out that KRK was a good company until Gibson bought them. Their
original monitors are quite good. In fact, they turned my head at the
AES convention where they were debuted.





== 15 of 16 ==
Date: Sat, Oct 5 2013 5:47 am
From: "William Sommerwerck"


"Phil Allison" wrote in message news:bbab1iFbl9iU1@mid.individual.net...

> Just what do you think you are doing -- Dave ??

"I can feel my mind going, Dave. Thee is no question about it."




== 16 of 16 ==
Date: Sat, Oct 5 2013 6:32 am
From: "Gareth Magennis"




"William Sommerwerck" wrote in message news:l2p1q0$kq9$1@dont-email.me...

"Phil Allison" wrote in message news:bbab1iFbl9iU1@mid.individual.net...

> Just what do you think you are doing -- Dave ??

"I can feel my mind going, Dave. Thee is no question about it."




http://www.youtube.com/watch?v=41U78QP8nBk





==============================================================================
TOPIC: What to do when a key stops working on a Laptop keyboard?
http://groups.google.com/group/sci.electronics.repair/t/bbd9adad1ab1364d?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Oct 3 2013 7:58 pm
From: gregz


"William Sommerwerck" <grizzledgeezer@comcast.net> wrote:
> Do you have a can of aerosol duster? If there's something blocking the
> key's movement, it might dislodge it without having to pop the cap.

I often turn keyboard upside down while doing that.

Greg





==============================================================================
TOPIC: alliance antenna rotor
http://groups.google.com/group/sci.electronics.repair/t/60e644314adaefab?hl=en
==============================================================================

== 1 of 3 ==
Date: Fri, Oct 4 2013 2:05 pm
From: "hrhofmann@sbcglobal.net"


What does a rotor have to do with a DVR, the rotor only orients the antenna unles you have found some new use for one!




== 2 of 3 ==
Date: Fri, Oct 4 2013 2:18 pm
From: Michael Black


On Fri, 4 Oct 2013, hrhofmann@sbcglobal.net wrote:

> What does a rotor have to do with a DVR, the rotor only orients the
> antenna unles you have found some new use for one!
>
It would be far easier to follow what you were getting at if you actualy
quoted what you were replying to. google isn't Usenet, the rest of us see
it differently.

And if you need the antenna pointed in this direction for one channel, and
in that direction for another channel, then when you program the DVR to
record something on this channel and then that channel, the antenna
doesn't follow along. One of the channels won't be received, because the
antenna is not pointing the right way.

I have a similar problem with my DTV set. When I use my home made
multi-bowtie antenna, it's directional enough that when aimed for the US
channels, I miss some of the local channels. No problem, I can just shift
the antenna a bit, it's indoors. But, since the tv set doesn't let me
program in the "local channels", I have to do a scan. And it won't get
all the channels because the antenna is too directional. I did solve
that, put a loop on a longer piece of coax, hang the loop from a long
piece of bamboo pole, and stick that out the window. It gets enough
signal in all directions for the scan to get all the channels I'll get,
though some don't actually present a picture with that loop. Then I can
use the bowtie array, aiming it as needed.

Michael







== 3 of 3 ==
Date: Sat, Oct 5 2013 8:26 pm
From: stratus46@yahoo.com


On Friday, October 4, 2013 2:05:21 PM UTC-7, hrho...@sbcglobal.net wrote:
> What does a rotor have to do with a DVR, the rotor only orients the antenna unles you have found some new use for one!

You're really asking such a silly question? I have computers recording TV 6 nights a week. You go turning the antenna and the reception goes bye bye. I don't know of any recording software that could re-aim the antenna first. If it were mine, I'd forgo the rotator and use multiple antennas and then jointenna diplexers to make one clean RF feed where all channels are available all the time. A private MATV system.

G²





==============================================================================
TOPIC: IC Identification Help (SMD Marking 651+, or maybe G51+), SOT-23-6
http://groups.google.com/group/sci.electronics.repair/t/03b5c5812be29ee3?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 5 2013 12:57 am
From: pdaderko@yahoo.com


Quick update... the parts arrived from Digikey today, and I replaced the NDC651N with the SI3454ADV-T1-E3 (pin 6 bent up and over to pin 5), and it worked great.

Pat





==============================================================================
TOPIC: Converting a 200W discharge lamp video projector to LED
http://groups.google.com/group/sci.electronics.repair/t/c84c8e901a969276?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 5 2013 7:01 am
From: N_Cook


The focused 7 cell honeycomb lens came together well. Doing the maths
and having a wedge tapering to .3mm seemed ok but trying to adapt
plastic to those sorts of dimensions is not practical. Having to mould
my own mounts.
The 2700K LEDs are noticeably cream yellow colour to the eye and seem to
have supressed the blue peak, too much?
Relative intensity through a dicroic colourwheel
R 340
G 270
B 070
even the reflection off the blue filter, ie complement colour of yellow
, is noticeably brighter than the reflections off the R and G sections.
I was expecting to add 5mm red LEDs but looks as though it will have to
be blue ones. Won't know for sure until the video projector has a
reasonable block of time to get inside to mess about.





==============================================================================
TOPIC: Dual Channel Software Oscilloscope Ver 2.0
http://groups.google.com/group/sci.electronics.repair/t/fccc843f2ff99948?hl=en
==============================================================================

== 1 of 1 ==
Date: Sat, Oct 5 2013 10:53 pm
From: Scott Smith


Dual Channel Software Oscilloscope Ver 2.0
Uses your sound card line input for input
Single and Dual Trace Mode, Multiple Inputs
Six Trigger Modes, Auto / Manual Gain Mode
AC / DC, Normal / Triggered, Normal / Inverted Modes
Use soud Card Line Inputs for Input
Very Cheap Price (Special) $20 via Paypal.
Unlimited Support For Registered Users
http://www.vehiclerepair.org/scope/scope.html





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