Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
On Mon, 14 May 2012 19:01:55 -0400 (EDT) gandal...@aol.com wrote: 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. Do you mean Plastik 70 or Urethan 71 from Kontakt Chemie? At least that's what we use when we do not have high requirements. For implants we usually use a parylene coating, which does a very good job in keeping the moisture out that the epoxy lets trough. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
On Mon, 14 May 2012 19:43:47 -0600 Tom Knox act...@hotmail.com wrote: What type of coating do you recommend? What is the downside of coating all electronics? As i wrote before, we usually use Plastik 70 and Urethan 71 for the stuff that does not need high specs. For those that are under water and/or more aggresive stuff (like body fluids) we use parylene. The down side is that it costs money (it needs a manual step) and it makes reworks more difficult as you have to ensure that after the rework the coating is made watertight again (which isn't as easy as it looks). Oh.. and connectors are really a pain with any coating. Either you coat them as well and lose the connectivity or you have a point where water can creep under the coating. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
I really don't know who actually made it, what we generally used came from RS Components as an aerosol spray and Farnell carried a similar product. It was an RS own brand product, indicated as suitable for protecting circuit boards and probably marked up as something exciting, like printed circuit board spray:-) I've just checked the RS web site and can't find anything similar to what I remember, but it was quite a long time ago, probably over thirty years ago when I first specified it and at least ten since I had any involvement. I wasn't looking to satisfy any particular requirement other than my own specification, there was no certification or compliance requirement in this instance so using a generic product wasn't an issue, but it checked out ok and, on some sites at least, the protected boards would have run continuously for 20 years plus, so I guess it did a reasonable job:-) Anyway, we've rather drifted off topic again and I wasn't intending to do that, but it's good to hear that Paul seems to be close to up and running again. regards Nigel GM8PZR In a message dated 15/05/2012 08:07:12 GMT Daylight Time, att...@kinali.ch writes: On Mon, 14 May 2012 19:01:55 -0400 (EDT) gandal...@aol.com wrote: 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. Do you mean Plastik 70 or Urethan 71 from Kontakt Chemie? At least that's what we use when we do not have high requirements. For implants we usually use a parylene coating, which does a very good job in keeping the moisture out that the epoxy lets trough. Attila Kinali ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
What type of coating do you recommend? What is the downside of coating all electronics? As i wrote before, we usually use Plastik 70 and Urethan 71 for the stuff that does not need high specs. For those that are under water and/or more aggresive stuff (like body fluids) we use parylene. More or less the same product as Plastik 70 (spray) is Acrylic Conformal coating from Ambersil which is perhaps better known in other countries. Both companies belong to CRC.com. Both coatings are low viscosity, solvent-drying, acrylic based conformal coatings with excellent insulating properties (diel. strength 80kV/mm), developed specially to protect pc-boards. The down side is that it costs money (it needs a manual step) and it makes reworks more difficult as you have to ensure that after the rework the coating is made watertight again (which isn't as easy as it looks). Oh.. and connectors are really a pain with any coating. Either you coat them as well and lose the connectivity or you have a point where water can creep under the coating. If I remember well there is no water creeping under these acrylic coatings at normal conditions and they remain somewhat eleastic. For repair works at least PLASTIK 70 can be soldered through or be totally removed with acetone. Urethane is a very good coating but can only be removed by abrasion/ scratching. The product information sheets I found here: http://www.crcind.com/wwwcrc/tds/TKC3%20PLASTIK70.PDF http://www.crcind.com/wwwcrc/tds/TAI3%20CONFC.PDF Don't forget to read the safety information sheets which are as well available from the manufacturer. regards Arnold ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
Hi If you actually have to get the product through full humidity and salt spray testing *plus* make it work in the real world - go with the Parylene. The two part urethane coatings are pretty good, the acrylics are nearly transparent. Bob On May 15, 2012, at 3:21 AM, Attila Kinali wrote: On Mon, 14 May 2012 19:43:47 -0600 Tom Knox act...@hotmail.com wrote: What type of coating do you recommend? What is the downside of coating all electronics? As i wrote before, we usually use Plastik 70 and Urethan 71 for the stuff that does not need high specs. For those that are under water and/or more aggresive stuff (like body fluids) we use parylene. The down side is that it costs money (it needs a manual step) and it makes reworks more difficult as you have to ensure that after the rework the coating is made watertight again (which isn't as easy as it looks). Oh.. and connectors are really a pain with any coating. Either you coat them as well and lose the connectivity or you have a point where water can creep under the coating. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-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, arnold.ti...@gmx.de 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
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, gandal...@aol.com 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, arnold.ti...@gmx.de 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
We use the Plastik70 from Kontakt chemie On Tue, May 15, 2012 at 1:23 AM, Michael Blazer mbla...@satx.rr.com 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, gandal...@aol.com 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, arnold.ti...@gmx.de 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
If you can keep the boards in a vertical mount position, and they have been sprayed with a conformal coating, the heat from the components and the coating will keep any moisture from forming on the boards in a vertical position. We do this in several products we supply to the military. Dr Joe Palsa k3wry In a message dated 5/14/2012 9:03:13 P.M. Eastern Daylight Time, gandal...@aol.com writes: 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, arnold.ti...@gmx.de 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
What type of coating do you recommend? What is the downside of coating all electronics? Thomas Knox From: k3...@aol.com Date: Mon, 14 May 2012 21:16:15 -0400 To: time-nuts@febo.com Subject: Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa... If you can keep the boards in a vertical mount position, and they have been sprayed with a conformal coating, the heat from the components and the coating will keep any moisture from forming on the boards in a vertical position. We do this in several products we supply to the military. Dr Joe Palsa k3wry In a message dated 5/14/2012 9:03:13 P.M. Eastern Daylight Time, gandal...@aol.com writes: 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, arnold.ti...@gmx.de 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 -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
k3...@aol.com said: If you can keep the boards in a vertical mount position, and they have been sprayed with a conformal coating, the heat from the components and the coating will keep any moisture from forming on the boards in a vertical position. We do this in several products we supply to the military. Does this help significantly for an antenna preamp that doesn't dissipate much power? How much power does a board have to dissipate to keep dry? I assume it depends upon the size of the board, but I doubt if it's linear. What's magic about vertical for keeping dry? I'd expect a vertical board to have better air flow and hence better cooling, but does that keep it dryer? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under wa...
I speculate that water runs off. But that said the preamp did run 4 years and I didn't really do anything special. In fact the preamps cleaned up and ready to be remounted tomorrow. But first I have to see what may have let the moisture in. At least was it something large that needs to be plugged etc. Thanks everyone Regards Paul. On Mon, May 14, 2012 at 10:39 PM, Hal Murray hmur...@megapathdsl.netwrote: k3...@aol.com said: If you can keep the boards in a vertical mount position, and they have been sprayed with a conformal coating, the heat from the components and the coating will keep any moisture from forming on the boards in a vertical position. We do this in several products we supply to the military. Does this help significantly for an antenna preamp that doesn't dissipate much power? How much power does a board have to dissipate to keep dry? I assume it depends upon the size of the board, but I doubt if it's linear. What's magic about vertical for keeping dry? I'd expect a vertical board to have better air flow and hence better cooling, but does that keep it dryer? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
