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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