sci.electronics.repair@googlegroups.com

Today's topics:

* How to dissolve clear plastic coat from circuit boards? - 4 messages, 4
authors
http://groups.google.com/group/sci.electronics.repair/t/3589eaf245b53d57?hl=en
* Discount Jordan10 - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/b7ea20e6569a4b3b?hl=en
* Cheap Wholesale Gucci real leather Purse - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/abbe2ee2a27801c9?hl=en
* CRT: Brief contrast/brightness prob at start-up. - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/cdf227264ff94f95?hl=en
* Crest Audio Pulse 2 1100 power amps, 1999 - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/8c6ed4787718ff07?hl=en
* Electric fence operation problem - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/eef28366a8aa3bbf?hl=en
* Repairing an expensive speaker - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/8fc3fa133c100ac4?hl=en

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

== 1 of 4 ==
Date: Thurs, Jul 8 2010 7:24 pm
From: dplatt@radagast.org (Dave Platt)

In article <PtKdnWFfL-8fzavRRVn_vwA@giganews.com>,
Robbie Hatley <see.my.sig@for.my.contact.info> 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".

MG chemicals makes one, which the MSDS says contains

1-methyl-2-pyrrolidinone
Dibasic Ester (Mixture)
Dimethyl Glutarate 55-65%
Dimethyl Adipate 10-25%
Dimethyl Succinate 15-25%
D'Limonene

Another source might be Miller-Stephenson (their D0319B or
MS-115 strippers)... the former handles both urethane and epoxy
coatings, the latter is optimized for epoxy.

Conformal coatings may be urethane, epoxy, acrylic, or silicone. I
believe that the urethane types are the most common but I could well
be wrong about taht. The pale-blue glow you observed is probably a
UV-fluorescent tracer dye, added to the liquid coating so that boards
can be checked during manufacture to ensure that they're properly
coated.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

== 2 of 4 ==
Date: Thurs, Jul 8 2010 8:09 pm
From: Sjouke Burry

William Sommerwerck wrote:
>> Try acetone.
>
> But with great caution. Acetone attacks a lot of plastics.
>
>
I would try MEK(Methyl-ethyl-keton) if you are still allowed
to use it. :)

== 3 of 4 ==
Date: Thurs, Jul 8 2010 10:13 pm
From: Jeff Liebermann

On Thu, 8 Jul 2010 19:24:02 -0700, dplatt@radagast.org (Dave Platt)
wrote:

>Conformal coatings may be urethane, epoxy, acrylic, or silicone. I
>believe that the urethane types are the most common but I could well
>be wrong about taht.

I think acrylic is the most popular these days. If it's hard as a
rock and clear, it's acrylic. If it's soft and yellowish, it's
urathane. If it's hard and yellowish, it's epoxy.

Go unto thy local paint or hardware store and get some urethane and
epoxy paint remover. Use it sparingly as it will attack G10 and FR4
PCB material, which is epoxy and fiberglass. Don't dunk the board
into the stuff. Just paint some on the area where you're working and
wipe it off when the coating gets soft. The rest of the way, use a
scraper.

>The pale-blue glow you observed is probably a
>UV-fluorescent tracer dye, added to the liquid coating so that boards
>can be checked during manufacture to ensure that they're properly
>coated.

Yep. Get a UV lamp (black light) so you can see where the coating is
missing.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

== 4 of 4 ==
Date: Fri, Jul 9 2010 12:41 am
From: "N_Cook"

Robbie Hatley <see.my.sig@for.my.contact.info> wrote in message
news:PtKdnWFfL-8fzavRRVn_vwA@giganews.com...
>
> 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?
>
> So far, I've tried:
>
> 91% isopropyl alcohol:
> Loosens bond between coat and board, but doesn't dissolve coat.
>
> Unknown solvent in unmarked 55-gallon drum (possibly toluene-based):
> Dissolves coat, but very slowly, requiring a lot of scrubbing with a
brush.
> Noxious fumes.
>
> CRC Letra-Motive Electric Parts Cleaner:
> Dissolves coat, but slowly, requiring a lot of scrubbing with a
brush.
> Turns coat into a thick goo that mucks-up brush and is hard to rinse
out.
> Noxious fumes.
>
> Are there better options?
>
> --
> Varnished,
> Robbie Hatley
> lonewolf [[at]] well [[dot]] com
>
>
>
>

I've seen that purple-blue glow flourescence effect , in sunlight (UV?),with
some formulations of hotmelt glue. Try a soldering iron somewhere on it.
Makes as much sence using hot melt glue as a conformal coating as the
paraffin wax covering a board I'm wrestling with recently. But other than
for gluing down large lumps to pcbs I've never seen a covering with it but
as the low temp formulation melts at 70 deg c or so a bath of it could make
a conformal dip treatment.

==============================================================================
TOPIC: Discount Jordan10
http://groups.google.com/group/sci.electronics.repair/t/b7ea20e6569a4b3b?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jul 8 2010 8:38 pm
From: jialiushoes

?^_^? 2010 High quality Discount Nike Jordan shoes at website:
http://www.jialiuonline.com/ <paypal payment>

Discount brand shoes

http://www.jialiuonline.com/FOOTWEAR-Air%20jordan%201-151/

Discount Nike Jordan shoes

http://www.jialiuonline.com/FOOTWEAR-Air%20jordan%201-151/

Discount Jordan1

http://www.jialiuonline.com/FOOTWEAR-Air%20jordan%201-151/

Discount Jordan1.5

http://www.jialiuonline.com/FOOTWEAR-Air%20jordan%201-151/

Discount Jordan2

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%202-152/

Discount Jordan2.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%203-153/

Discount Jordan3

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%203-153/

Discount Jordan3.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%203-153/

Discount Jordan4

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%204-154/

Discount Jordan7 Boots

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%204-154/

Discount Jordan4.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%204-154/

Discount Jordan8 Boots

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%204-154/

Discount Jordan5.5 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%205-155/

Discount Jordan5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%205-155/

Discount Jordan6

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%206-156/

Discount J6.5 Kid

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%206-156/

Discount Jordan7

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%207-157/

Discount Jordan7.5 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%207-157/

Discount Jordan8

http://www.jialiuonline.com/FOOTWEAR-Air%20jordan%208%20(lady)-929/

Discount Jordan9

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%209-159/

Discount Jordan9.5 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%209-159/

Discount Jordan10

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2010-160/

Discount Jordan11

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2011-161/

Discount Jordan11.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2011-161/

Discount Jordan12

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2012-162/

Discount Jordan12.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2012-162/

Discount Jordan13

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2013-163/

Discount Jordan14

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2014-164/

Discount Jordan15 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2014-164/

Discount Jordan15.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2014-164/

Discount Jordan16

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan17

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan18

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan19

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan19.5

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan22 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan22.5 Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2016-166/

Discount Jordan23

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2023-170/

Discount Jordan24

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%2023-170/

Discount Air Yeezy Man

http://www.jialiuonline.com/FOOTWEAR-Air%20Jordan%206+Yeezy-149/

Discount J1+J2+J5+J7 Man

http://www.jialiuonline.com/FOOTWEAR-J12&J13-181/

Discount Jordan3+Jordan5+Jordan15

http://www.jialiuonline.com/FOOTWEAR-J12&J13-181/

Discount Jordan23+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan3+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan4+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan4.5+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan5+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan6+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan9+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan9+Jordan23 Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11.5+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+Anthony

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+Jordan12

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+Jordan13

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+Jordan23

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan11+Obama

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan12+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan13+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan13+AJ6Rings

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan16.5+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount J18+J23 Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan20+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount J21+J23 Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan25+AF1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan 6unite1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan 8unite1

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan flying Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan foamposite liite Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan MELO M5 Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount JORDAN TRUE FLIGHT Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Discount Jordan Trunner Q4 Man

http://www.jialiuonline.com/FOOTWEAR-J11.5&AF1-203/

Cheap wholesale more brand shoes at WEBSITE:
http://www.jialiuonline.com/

==============================================================================
TOPIC: Cheap Wholesale Gucci real leather Purse
http://groups.google.com/group/sci.electronics.repair/t/abbe2ee2a27801c9?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Jul 8 2010 8:40 pm
From: jialiujeans

AAA real leather Handbags http://www.jialiuonline.com/
Cheap Wholesale Balenciaga real leather Handbags
Cheap Wholesale Balenciaga real leather Purse
Cheap Wholesale Bally real leather Purse <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale BOSS real leather Purse
Cheap Wholesale Burberry real leather Handbags
Cheap Wholesale Chanel real leather Handbags <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Chanel real leather Purse
Cheap Wholesale Chloe real leather Handbags
Cheap Wholesale Chloe real leather Purse <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Coach real leather Handbags
Cheap Wholesale Coach real leather Purse
Cheap Wholesale D&G real leather Handbags
Cheap Wholesale D&G real leather Purse
Cheap Wholesale Dior real leather Handbags <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Dunhill real leather Purse
Cheap Wholesale Fendi real leather Handbags <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Gucci real leather Handbags
Cheap Wholesale Gucci real leather Purse
Cheap Wholesale Hermes real leather Handbags
Cheap Wholesale Hermes real leather Purse <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Jimmy Choo real leather Handbags
Cheap Wholesale Jimmy Choo real leather Purse
Cheap Wholesale Juicy real leather Handbags
Cheap Wholesale Kooba real leather Handbags
Cheap Wholesale Lancel real leather Handbags
Cheap Wholesale Loewe real leather Handbags
Cheap Wholesale LV real leather Handbags <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale LV real leather Purse
Cheap Wholesale Marc Jacobs real leather Handbags
Cheap Wholesale Miumiu real leather Handbags
Cheap Wholesale burberry real leather Handbags
Cheap Wholesale Prada real leather Handbags <free shipping paypal
payment> http://www.jialiuonline.com/
Cheap Wholesale Prada real leather Purse
Cheap Wholesale Thomaswlde real leather Handbags
Cheap Wholesale Valentnv real leather Handbags
Cheap Wholesale Versace real leather Handbags <free shipping paypal
payment>
website: http://www.jialiuonline.com/

==============================================================================
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: Thurs, Jul 8 2010 11:34 pm
From: Meatman

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!

==============================================================================
TOPIC: Crest Audio Pulse 2 1100 power amps, 1999
http://groups.google.com/group/sci.electronics.repair/t/8c6ed4787718ff07?hl=en
==============================================================================

== 1 of 1 ==
Date: Fri, Jul 9 2010 12:35 am
From: "N_Cook"

Owner has 5 of these and 3 have gone into protect mode, all the same
symptoms. All look the same but not sequential serial numbers. He's getting
someone technical to look at the speakers and leads and as they are used
from a diesel generator maybe a problem there. All failed in use , not
abuse, not failing at switch on , and no earlier odd noises before failing.
Anyway these 3 amps show clip LED on both ch, and then drop into protect.
I've the schematics for them but before going down false paths ,anyone been
here before. ? I've looked inside one and all healthy appearance. SMPS fires
up enough to deliver about +/- 100V rails, both ch, for half a second , fans
ok and relays click over but then drops into protect. No excessive mains
current draw at any time.
This one and the others , both channel o/p measure about 13 to 15K to ground
and not tied to + or - rails so will assume PAs are ok at this stage and
maybe falsely going into protect.

==============================================================================
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 12:45 am
From: "N_Cook"

Franc Zabkar <fzabkar@iinternode.on.net> wrote in message
news:8fnc361ijlnbv0spgbgljmn7tfdo8nfpe2@4ax.com...
> On Thu, 8 Jul 2010 08:24:40 +0100, "N_Cook" <diverse@tcp.co.uk> put
> finger to keyboard and composed:
>
> >The cap is 1uF , 280V ac rating. From the .5*C*V*V that comes to 630V, so
> >something awry there.
> >No more than 250V m 60% of likely DC rating, and I would have thought
more
> >like an equal split between 12V and 1800V so about 150V, transformers are
> >much the same size if that is anything to go by
>
> If the device is designed to output its rated energy over a 9V-12V
> supply range, then one would expect that the dump capacitor's voltage
> would be regulated. Otherwise the variation in the stored energy would
> be (12/9)^2 = 1.8X.
>
> Is there any voltage feedback from the dump cap back to its charge
> controller? I'd expect to see a resistive potential divider feeding
> one input of an error amp (comparator?), and maybe a 5V or 2.5V
> reference on the other input. You may be able to compute the voltage
> from the resistance values.
>
> - Franc Zabkar
> --
> Please remove one 'i' from my address when replying by email.

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

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

== 1 of 1 ==
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.

>

==============================================================================

You received this message because you are subscribed to the Google Groups "sci.electronics.repair"
group.

To post to this group, visit http://groups.google.com/group/sci.electronics.repair?hl=en

To unsubscribe from this group, send email to sci.electronics.repair+unsubscribe@googlegroups.com

To change the way you get mail from this group, visit:
http://groups.google.com/group/sci.electronics.repair/subscribe?hl=en

To report abuse, send email explaining the problem to abuse@googlegroups.com

==============================================================================
Google Groups: http://groups.google.com/?hl=en