That sounds like what we use in the AeroSpace industry. I remember the UV dye. Thanks
Thomas Knox > Date: Mon, 14 May 2012 21:13:55 -0400 > From: [email protected] > To: [email protected] > Subject: Re: [time-nuts] Conformal Coating > > For conformal coating I recommend Humiseal Acrylic 1B73 in aerosol. You can > also get it in brush form. I believe that Chemtronics used to offer acrylic > coating as well, maybe even re-packaging the Humiseal product. I don't know > if there is a source for small quantities of Humiseal but it is a fine > product. > > I have also used Krylon clear acrylic that you can get at Wall-Mart in a > pinch. The acrylic coatings I have found are better for HiZ circuits that > have requirements for low-leakage. Consult the can for solvents and make > sure that what you are coating are compatible with Toluene, Ketones, > Acetone, etc. be careful around connectors as the coating will wick into > connectors as the 1B73 is a fairly low viscosity. You can also get Humiseal > formulations 1B38 and 1B66 which are also Acrylics but are brush on and > require a one gallon minimum purchase. The shipping cost for a gallon is > almost as much as the product due to the requirement that it be shipped as > a hazardous material (flameable). The acrylics can be dissolved with MEK or > any of the solvents I have listed above. You can remove a small amount with > a Q-Tip. > > The Humiseal product also has a UV indicator in it that glows blue under a > black light so you can check coverage. > > I have tested Humiseal Acrylic on probably 1000+ PCB's and it has yet to > fail me. It is also easy to rework and re-coat after repairs. > > You can also get polyurethane coatings but I do not recommend them since > they are more difficult you use, not as easy to remove > and have better performance for HiZ and RF circuits. > > Good luck and let us know how you make out. > > Sam > W3OHM > > http://www.hmcelectronics.com/product/Chemtronics/CTAR12 > > > > > On Mon, May 14, 2012 at 7:31 PM, <[email protected]> wrote: > > > Send time-nuts mailing list submissions to > > [email protected] > > > > To subscribe or unsubscribe via the World Wide Web, visit > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > or, via email, send a message with subject or body 'help' to > > [email protected] > > > > You can reach the person managing the list at > > [email protected] > > > > When replying, please edit your Subject line so it is more specific > > than "Re: Contents of time-nuts digest..." > > > > > > Today's Topics: > > > > 1. Re: Why are 1PPS signals so skinny? (Jim Hickstein) > > 2. Re: Why are 1PPS signals so skinny? (Azelio Boriani) > > 3. Re: wwvb weak on east coast especially when the pre-amps > > under wa... (Michael Blazer) > > 4. Re: wwvb weak on east coast especially when the pre-amps > > under wa... (Azelio Boriani) > > 5. Re: Why are 1PPS signals so skinny? (Michael Blazer) > > 6. Re: Why are 1PPS signals so skinny? (Bob Camp) > > 7. Re: wwvb weak on east coast especially when thepre-amps under > > wa... (Alan Melia) > > > > > > ---------------------------------------------------------------------- > > > > Message: 1 > > Date: Mon, 14 May 2012 18:18:20 -0500 > > From: Jim Hickstein <[email protected]> > > To: [email protected] > > Subject: Re: [time-nuts] Why are 1PPS signals so skinny? > > Message-ID: <[email protected]> > > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > > > On 2012/05/14 18:02, [email protected] wrote: > > > https://assist.daps.dla.mil/quicksearch/ is the search site for > > military standards. > > > > Hmm. Doesn't find MIL-TGDBP-41. I got this from my (now late) great > > uncle, Bob > > Sedgwick -- who was to hydraulics what I am to computers, only he has a > > number > > of patents. > > > > Some smart-aleck at Wright Field, as it then was, put this on a drawing, > > and it > > went without comment for quite a while until someone tried to look it up. > > This > > escalated to a bird colonel, who then tracked down the miscreant. > > > > It stands for Make It Like The G-D Blueprint For Once. > > > > > > > > ------------------------------ > > > > Message: 2 > > Date: Tue, 15 May 2012 01:21:26 +0200 > > From: Azelio Boriani <[email protected]> > > To: Discussion of precise time and frequency measurement > > <[email protected]> > > Subject: Re: [time-nuts] Why are 1PPS signals so skinny? > > Message-ID: > > <CAL8XPmOc8cLJ3aGBcqJsJB=fbw5xtq-_fy54r9eddudux+a...@mail.gmail.com > > > > > Content-Type: text/plain; charset=ISO-8859-1 > > > > Maybe the correct number is MIL-STD-188-115? > > > > On Tue, May 15, 2012 at 1:18 AM, Jim Hickstein <[email protected]> wrote: > > > > > On 2012/05/14 18:02, [email protected] wrote: > > > > > >> https://assist.daps.dla.mil/quicksearch/ is the search site for > > >> military standards. > > >> > > > > > > Hmm. Doesn't find MIL-TGDBP-41. I got this from my (now late) great > > > uncle, Bob Sedgwick -- who was to hydraulics what I am to computers, only > > > he has a number of patents. > > > > > > Some smart-aleck at Wright Field, as it then was, put this on a drawing, > > > and it went without comment for quite a while until someone tried to look > > > it up. This escalated to a bird colonel, who then tracked down the > > > miscreant. > > > > > > It stands for Make It Like The G-D Blueprint For Once. > > > > > > > > > _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > ------------------------------ > > > > Message: 3 > > Date: Mon, 14 May 2012 18:23:31 -0500 > > From: Michael Blazer <[email protected]> > > To: [email protected] > > Subject: Re: [time-nuts] wwvb weak on east coast especially when the > > pre-amps under wa... > > Message-ID: <[email protected]> > > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > > > Here's comparison for various type of conformal coating: > > http://mgchemicals.com/downloads/appguide/appguide0404.pdf.< > > https://assist.daps.dla.mil/quicksearch/> > > > > I think there is a type that is 'serviceable' and removable with alcohol. > > > > Mike > > > > On 5/14/2012 6:01 PM, [email protected] wrote: > > > The other option of course is to pressurise the box with dry air to > > ensure > > > a positive pressure differential, such that the net flow is always > > outwards > > > at all points, but it's probably easier just to provide a drain hole:-) > > > > > > However, whilst a drain hole will prevent the build up of a lake inside > > the > > > enclosure it still doesn't prevent condensation forming on circuit > > boards, > > > and powered circuit boards and condensation don't really go well > > together. > > > > > > As per earlier comments, it's quite difficult to keep any externally > > > mounted enclosure totally moisture free, so it's much easier to accept > > the > > > inevitable and allow for it. > > > > > > In a past life I designed quite a few circuit boards that were required > > to > > > be fitted in externally mounted vented enclosures, so not a great deal > > of > > > pressurisation there then:-), and I usually specified that both sides > > > should be sprayed with a plastic coating following final test. > > > > > > I can't remember now exactly what this stuff was called, but it was > > > readily available in the UK from both RS and Farnell as an aerosol > > plastic spray > > > that provided a good barrier but was a bit more flexible than the usual > > MOD > > > spec conformal coatings. > > > It melted easily under a soldering iron, albeit with a foul pong:-), so > > > reworking was no problem, and resisted moisture remarkably well..... > > > > > > problem solved:-) > > > > > > Nigel > > > GM8PZR > > > > > > > > > > > > > > > > > > In a message dated 14/05/2012 23:10:30 GMT Daylight Time, > > > [email protected] writes: > > > > > > The only solutions I think: > > > Apply air pressure tight boxes having a breathing hole an the bottom, > > > mount the > > > box that no rain and water can penetrate from the top or sides. If the > > > hole is big enough, > > > eg. 2mm, no pressure difference is possible and no pumping effect will > > > occur. > > > (If the hole is too wide, small animals may penetrate). > > > Or, > > > when using a pressure tight box, it must be stiff and sealed to > > > withstand under all > > > temperature conditions more then 1 bar/ 100 kPa. Do not forget that all > > > feed > > > throughs must be of real hermetic type, normal coaxial connectors are > > > not tight! > > > Don't route cables directly in, because no cable braid or mesh is vapor > > > tight. > > > _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > > > > ------------------------------ > > > > Message: 4 > > Date: Tue, 15 May 2012 01:25:54 +0200 > > From: Azelio Boriani <[email protected]> > > To: Discussion of precise time and frequency measurement > > <[email protected]> > > Subject: Re: [time-nuts] wwvb weak on east coast especially when the > > pre-amps under wa... > > Message-ID: > > <cal8xpmpcb-dwcpot0nmfp+tdpdrck-xjxxvjwytja+rqmux...@mail.gmail.com > > > > > Content-Type: text/plain; charset=ISO-8859-1 > > > > We use the Plastik70 from Kontakt chemie > > > > On Tue, May 15, 2012 at 1:23 AM, Michael Blazer <[email protected]> > > wrote: > > > > > Here's comparison for various type of conformal coating: > > > http://mgchemicals.com/downloads/appguide/appguide0404.pdf.< > > > https://assist.daps.dla.mil/quicksearch/> > > > > > > I think there is a type that is 'serviceable' and removable with alcohol. > > > > > > Mike > > > > > > > > > On 5/14/2012 6:01 PM, [email protected] wrote: > > > > > >> The other option of course is to pressurise the box with dry air to > > ensure > > >> a positive pressure differential, such that the net flow is always > > >> outwards > > >> at all points, but it's probably easier just to provide a drain hole:-) > > >> > > >> However, whilst a drain hole will prevent the build up of a lake inside > > >> the > > >> enclosure it still doesn't prevent condensation forming on circuit > > >> boards, > > >> and powered circuit boards and condensation don't really go well > > >> together. > > >> > > >> As per earlier comments, it's quite difficult to keep any externally > > >> mounted enclosure totally moisture free, so it's much easier to accept > > the > > >> inevitable and allow for it. > > >> > > >> In a past life I designed quite a few circuit boards that were required > > >> to > > >> be fitted in externally mounted vented enclosures, so not a great deal > > of > > >> pressurisation there then:-), and I usually specified that both sides > > >> should be sprayed with a plastic coating following final test. > > >> > > >> I can't remember now exactly what this stuff was called, but it was > > >> readily available in the UK from both RS and Farnell as an aerosol > > >> plastic spray > > >> that provided a good barrier but was a bit more flexible than the usual > > >> MOD > > >> spec conformal coatings. > > >> It melted easily under a soldering iron, albeit with a foul pong:-), so > > >> reworking was no problem, and resisted moisture remarkably well..... > > >> > > >> problem solved:-) > > >> > > >> Nigel > > >> GM8PZR > > >> > > >> > > >> > > >> > > >> > > >> In a message dated 14/05/2012 23:10:30 GMT Daylight Time, > > >> [email protected] writes: > > >> > > >> The only solutions I think: > > >> Apply air pressure tight boxes having a breathing hole an the bottom, > > >> mount the > > >> box that no rain and water can penetrate from the top or sides. If the > > >> hole is big enough, > > >> eg. 2mm, no pressure difference is possible and no pumping effect will > > >> occur. > > >> (If the hole is too wide, small animals may penetrate). > > >> Or, > > >> when using a pressure tight box, it must be stiff and sealed to > > >> withstand under all > > >> temperature conditions more then 1 bar/ 100 kPa. Do not forget that > > all > > >> feed > > >> throughs must be of real hermetic type, normal coaxial connectors are > > >> not tight! > > >> Don't route cables directly in, because no cable braid or mesh is > > vapor > > >> tight. > > >> _______________________________________________ > > >> time-nuts mailing list -- [email protected] > > >> To unsubscribe, go to > > >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > >> and follow the instructions there. > > >> > > >> > > >> _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > ------------------------------ > > > > Message: 5 > > Date: Mon, 14 May 2012 18:26:58 -0500 > > From: Michael Blazer <[email protected]> > > To: [email protected] > > Subject: Re: [time-nuts] Why are 1PPS signals so skinny? > > Message-ID: <[email protected]> > > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > > > I haven't heard that one before. I try to slip in the TLAR check in all > > the test procedures I write. When 'they' ask, I look at it and say: > > "That Looks About Right". > > Mike > > > > On 5/14/2012 6:18 PM, Jim Hickstein wrote: > > > On 2012/05/14 18:02, [email protected] wrote: > > >> https://assist.daps.dla.mil/quicksearch/ is the search site for > > >> military standards. > > > > > > Hmm. Doesn't find MIL-TGDBP-41. I got this from my (now late) great > > > uncle, Bob Sedgwick -- who was to hydraulics what I am to computers, > > > only he has a number of patents. > > > > > > Some smart-aleck at Wright Field, as it then was, put this on a > > > drawing, and it went without comment for quite a while until someone > > > tried to look it up. This escalated to a bird colonel, who then > > > tracked down the miscreant. > > > > > > It stands for Make It Like The G-D Blueprint For Once. > > > > > > _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > > > > > > ------------------------------ > > > > Message: 6 > > Date: Mon, 14 May 2012 19:30:49 -0400 > > From: Bob Camp <[email protected]> > > To: Discussion of precise time and frequency measurement > > <[email protected]> > > Subject: Re: [time-nuts] Why are 1PPS signals so skinny? > > Message-ID: <[email protected]> > > Content-Type: text/plain; charset=iso-8859-1 > > > > Hi > > > > I would bet that the basic electrical definition of the "skinny" PPS dates > > at least to the mid 50's if not earlier. > > > > Bob > > > > On May 14, 2012, at 3:20 PM, Magnus Danielson wrote: > > > > > Mark, Azelio and Bj?rn, > > > > > > On 05/14/2012 06:33 PM, [email protected] wrote: > > >> Mark& Azelio, > > >> > > >> Or even 10V into 50ohm, 20us... See figure 3-4 in ICD-GPS-060. > > >> > > >> http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf > > >> > > >> More modern 3-5.5V into 50ohm, 20us. > > >> > > http://contracting.tacom.army.mil/majorsys/jab/DAGR%20Interface%20Specification.pdf > > >> > > >> Above are two standards demanding short skinny 1PPS pulses. Are there > > any > > >> other standards with distinct shape requirements on 1PPS pulses? > > > > > > You need to look at MIL STD 188/155 which if I recall things was > > initially formed in the 60thies. > > > > > > An AccuBeat presentation actually says that the PPS was originally > > defined in it. > > > > > > The MIL STD 188/155 is actually a 10 V peak level, so it was much hotter > > than we are used to know. It specified 5 MHz as base frequency, or power of > > 2 multiples (10, 20, 40 MHz... ). > > > > > > It was later reformulated in the PTTI spec, which ICD GPS 060 is a > > derivate. The 50 ns rise and 1 us fall slopes comes from that spec. > > > > > > I was not able to find MIL STD 188-155 on the net right now, but I have > > been able to download it before, so if someone is a more lucky it should > > surface. I should have my download somewhere. > > > > > > Cheers, > > > Magnus > > > > > > _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > > ------------------------------ > > > > Message: 7 > > Date: Tue, 15 May 2012 00:32:11 +0100 > > From: "Alan Melia" <[email protected]> > > To: "Discussion of precise time and frequency measurement" > > <[email protected]> > > Subject: Re: [time-nuts] wwvb weak on east coast especially when > > thepre-amps under wa... > > Message-ID: <012501cd3229$cb66eae0$4001a8c0@lark> > > Content-Type: text/plain; charset="iso-8859-1" > > > > Well almost Nigel, if you look at molecule mean velocities they are always > > able to diffuse down a concentration gradient (i.e from wet into dry) > > despite a small reverse presure gradient. It just takes longer under those > > conditions :-))....which is often "enough" > > > > Alan G3NYK > > ----- Original Message ----- > > From: <[email protected]> > > To: <[email protected]> > > Sent: Tuesday, May 15, 2012 12:01 AM > > Subject: Re: [time-nuts] wwvb weak on east coast especially when > > thepre-amps > > under wa... > > > > > > > The other option of course is to pressurise the box with dry air to > > ensure > > > a positive pressure differential, such that the net flow is always > > outwards > > > at all points, but it's probably easier just to provide a drain hole:-) > > > > > > However, whilst a drain hole will prevent the build up of a lake inside > > the > > > enclosure it still doesn't prevent condensation forming on circuit > > boards, > > > and powered circuit boards and condensation don't really go well > > together. > > > > > > As per earlier comments, it's quite difficult to keep any externally > > > mounted enclosure totally moisture free, so it's much easier to accept > > the > > > inevitable and allow for it. > > > > > > In a past life I designed quite a few circuit boards that were required > > to > > > be fitted in externally mounted vented enclosures, so not a great deal > > of > > > pressurisation there then:-), and I usually specified that both sides > > > should be sprayed with a plastic coating following final test. > > > > > > I can't remember now exactly what this stuff was called, but it was > > > readily available in the UK from both RS and Farnell as an aerosol > > plastic > > spray > > > that provided a good barrier but was a bit more flexible than the usual > > MOD > > > spec conformal coatings. > > > It melted easily under a soldering iron, albeit with a foul pong:-), so > > > reworking was no problem, and resisted moisture remarkably well..... > > > > > > problem solved:-) > > > > > > Nigel > > > GM8PZR > > > > > > > > > > > > > > > > > > In a message dated 14/05/2012 23:10:30 GMT Daylight Time, > > > [email protected] writes: > > > > > > The only solutions I think: > > > Apply air pressure tight boxes having a breathing hole an the bottom, > > > mount the > > > box that no rain and water can penetrate from the top or sides. If the > > > hole is big enough, > > > eg. 2mm, no pressure difference is possible and no pumping effect will > > > occur. > > > (If the hole is too wide, small animals may penetrate). > > > Or, > > > when using a pressure tight box, it must be stiff and sealed to > > > withstand under all > > > temperature conditions more then 1 bar/ 100 kPa. Do not forget that all > > > feed > > > throughs must be of real hermetic type, normal coaxial connectors are > > > not tight! > > > Don't route cables directly in, because no cable braid or mesh is vapor > > > tight. > > > _______________________________________________ > > > time-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > and follow the instructions there. > > > > > > > > > > ------------------------------ > > > > _______________________________________________ > > time-nuts mailing list > > [email protected] > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > > > End of time-nuts Digest, Vol 94, Issue 89 > > ***************************************** > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
