Special for our loved laser doctor, Joyce.
/Inge
On 16 February 2013 16:48, Joyce Koo <[log in to unmask]> wrote:
> You are right. It was greyish shiny. Magic. Everything mount on piece
> of flat wood. Open face, no box.
> --------------------------
> Sent using BlackBerry
>
>
> ----- Original Message -----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Saturday, February 16, 2013 08:45 AM
> To: Joyce Koo
> Cc: [log in to unmask] <[log in to unmask]>
> Subject: Re: [TN] AR/UR Conformal coatings
>
> Sorry, Joyce, not quartz. Usually galena (lead sulphide) with a cat's
> whisker! Built one when I was ~10! Not ROHS witha galena crystal!!! :)
>
> Brian
>
> On 16/02/2013 14:44, Joyce Koo wrote:
> > Brian, remind me my brother built a quartz crystal radio for me way,way
> back. The type with a needle in the glass tube with pig tail wires hanging
> out. He was my hero for few years, especially, he is younger than me!
> (Was convinced and still is that God gave him more brain than mine:).
> > --------------------------
> > Sent using BlackBerry
> >
> >
> > ----- Original Message -----
> > From: Brian Ellis [mailto:[log in to unmask]]
> > Sent: Saturday, February 16, 2013 02:17 AM
> > To: [log in to unmask] <[log in to unmask]>
> > Subject: Re: [TN] AR/UR Conformal coatings
> >
> > Not for electrical purposes AFAIK. It is still used for French polishing
> > of wood but even that is largely displaced by synthetic resins, except
> > for valuable furniture. Talking of which, I'd be curious to know the
> > composition of the lacquer that the Japanese use for wood (tableware and
> > decorative items). I know it is tapped from trees in a similar way to
> > latex. (Shellac comes from an insect.)
> >
> > I think I made the oscilloscope, for my own amateur use (I was a ham) in
> > 1948 or 49. I was still a Uni student at the time (graduated 1951, when
> > I started military service). For the anecdote, I used a Puckle timebase,
> > with a pentode used as a constant current source to charge the
> > capacitors, giving a good linearity with sweep times from 1 sec to 10
> > microsecs. Bet that takes you back in time. How many here even know what
> > a pentode is?
> >
> > Another insulation I used was paraffin wax. I wound the high voltage
> > transformer by hand, using a quite fragile 36 SWG wire for the
> > secondary, with thin kraft paper for interleaving between the layers. It
> > took me several evenings. When it was finished and the laminations
> > inserted, I impregnated the lot in hot wax for several hours, hoping the
> > paper would absorb it. It lasted a couple of years before there was a
> > flashover between the HT winding and the electrostatic screen between
> > the primary and secondary windings!
> >
> > I'll be 81 in a couple of months (I'm now like a kid, saying he is
> > nearly six!!! :-) ) Must be what they mean by 'second childhood'!
> >
> > Brian
> >
> > On 16/02/2013 02:08, Inge Hernefjord wrote:
> >> Is shellac still used? / Inge
> >> PS. U worked 1940!!! How old are you, man??? I thought some 70+ but you
> >> must be 70+++
> >>
> >> On 16 February 2013 00:41, Brian Ellis <[log in to unmask]
> >> <mailto:[log in to unmask]>> wrote:
> >>
> >> Graham
> >>
> >> I used shellac/ethanol in the 1940s for the anode voltage (~1.8 kV)
> >> assembly for an oscilloscope I built using a 3BP1 war surplus CRT.
> >> No, I didn't clean first, but remember this was tag-to-tag wiring,
> >> not PCB.
> >>
> >> Between then and acrylics, I used a phenol-formaldehyde
> formulation.
> >>
> >> Brian
> >>
> >>
> >> On 16/02/2013 00:04, Graham Naisbitt wrote:
> >>
> >> Hello everybody - IR Here!
> >>
> >> Question1 - Adhesion
> >>
> >> IMHO the problem is often derived from the presence of
> >> surfactants that have not been correctly controlled in earlier
> >> processes. "Correctly controlled" I acknowledge is an ambiguous
> >> term, but you need to go back to each process step and ensure
> >> that the process has been properly carried out: Solder resist -
> >> soldering processes - masking processes etc..
> >>
> >> That said, the fact is that certain acrylic based coatings
> >> exhibit poor adhesion and one solution to this is to bake the
> >> assembly at around 80DegC for 4 to 8 hours and often this issue
> >> is ameliorated.
> >>
> >> Question 2 - What are the best AR and UR coatings asked by
> >> Michael Strong of MG Chemicals�.a competitor to HumiSeal et al
> >> so I need to be careful, and please don't complain if this
> seems
> >> too commercial, but since several of you asked...
> >>
> >> OK. First up, 1A33 was, to my knowledge - that is bound to be
> >> proved wrong - one of the very first single part urethanes
> >> rendering the coating process far easier and with less material
> >> waste compared to 2 part formulations. Also, it was TDI free.
> >>
> >> As for the subject of curing, I would prefer to see the
> >> following terms employed in the IPC-CC-830 Standard: Stage 1 =
> >> Tack Free; Stage 2 = Dry (for handling) and Stage 3 = Full
> cure.
> >>
> >> The product will reach Tack Free in around 30 to 45 minutes,
> >> ambient. Dry in 2 to 4 hours, ambient and full cure either, 12
> >> hour bake at 80C or it will need to be exposed to 80C to
> >> initiate the full cure. It is the oil used in the product that
> >> turns an amber colour with heat, but that's the trade-off for a
> >> more user-friendly product.
> >>
> >> 1B31 was first introduced in or around 1975. A single-part
> >> acrylic, its main advantage is total repairability. Tack-Free =
> >> 10 to 15 minutes ambient; Dry in around 1 hour, ambient and
> full
> >> cure in about 24 hours, ambient.
> >>
> >> In around 1979/80, believing that 1B31 represented a major
> >> protection breakthrough, I recall being properly admonished by
> a
> >> senior manager at GEC Avionics in Rochester - ENGLAND - that
> the
> >> first conformal coating ever used was a type of Shellac used on
> >> the very early radars fitted to various RAF aircraft from
> around
> >> 1942.
> >>
> >> So, 1B31 effectively grandfathers ALL acrylic coatings. 1A33
> >> replaced most 2 part urethane formulations. Rather similar to
> >> the story of Rolls Royce, they just make a better product and
> >> they have a terrific pedigree. They have many worthy
> competitors.
> >>
> >> BTW techies, for those who don't know, I essentially ceased
> >> involvement with HumiSeal when I sold my business to them in
> 2005.
> >>
> >> Graham Naisbitt
> >>
> >>
> >> On 15 Feb 2013, at 16:54, Inge Hernefjord
> >> <[log in to unmask] <mailto:[log in to unmask]>>
> wrote:
> >>
> >> Where is Coating Nosebite....Nicebitt...hm....__Naisbitt ?
> >>
> >> On 15 February 2013 08:14, Michael Strong
> >> <[log in to unmask]
> >> <mailto:[log in to unmask]>>wrote:
> >>
> >> Just a general query on what are the best AR and UR
> >> solvent-based coatings
> >> available. I know Humiseal and Elantas are big players
> >> but I'd like to
> >> know
> >> what are their big products and why.
> >>
> >>
> >>
> >>
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