Yep, Bob K,
You can join us old geezers on the bench in the park...
I did a lot of those old experiments that C.L. Stong wrote about. Neighbor's father worked at Shell Research and we could get him to "requsition" items we couldn't get elsewhere. One project I never was successful at was making electrets. Electrets are like magnets only instead of a magnetic field they contain a permanently embedded static electric charge. It takes a combination of waxes to be melted and mixed then allowed to harden between plates charged to a high voltage.
Eventually they became commercially viable in profesional "electret" microphones. The mike is basically a variable capacitor and the charge across the plates is modulated by sound waves impinging on a thin metalized teflon foil (one of the plates is sensitive to air movement). The funny thing is they call them condenser microphones - the term "condenser" hasn't been used for many decades, of course, replaced by the term "capacitor".
See http://en.wikipedia.org/wiki/The_Amateur_Scientist for a good history of the column.
Bob L.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Saturday, February 16, 2013 12:38 PM
To: [log in to unmask]
Subject: Re: [TN] AR/UR Conformal coatings - NTC
Hi,
Am I just out of the loop now days or is today's "Hand Building of Electronics" now the inserting of a board into a PCI slot or plugging in a USB connector?
I have this incredible book "The Amateur Scientist" which is amazing. See:
http://www.amazon.com/gp/customer-media/product-gallery/B000ICZI3Y/ref=cm_ci
u_pdp_images_0?ie=UTF8&index=0
I worry such "enthusiasm" is no longer socially acceptable? I hope not.
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Saturday, February 16, 2013 12:17 PM
To: [log in to unmask]
Subject: Re: [TN] AR/UR Conformal coatings - NTC
Mullard KT66! My first real HiFi amplifier power stage was p-p KT66 with a hand made Darlington output transformer, weight 8 kilograms! The power supply scared me with 600 V on electrolytes. One day, with cover removed, one of the series coupled caps fused and the wet content went as high as up to the ceiling. I used ECC803 as input stage, driver stage...don't remember.
Despite this monster, the output was not more than 30 Watts AB.
Also, remember building AM and FM receivers, hand coiled filters and resonance circuits, Colpitt local oscillator, lots of tuning capacitors and all wiring via ceramic xxx (what did we call them?). I will send some nostalgia photos to you, Bob, Brian and Steve.
Memory exactness failes with age, but I have a feeling that we were more of enthusiasts then, compared with youngsters are today.
Inge
On 16 February 2013 13:48, Bob Landman <[log in to unmask]> wrote:
> Brian,
>
> Of course I know what a pentode is and also can still recall the base
> wiring of most vacuum tubes (valves to you Brits). 2 & 7 are the
> filaments. My scope was a Heathkit with a 5UP1 (I've still got it in
> the cellar). I still have quite a collection of tubes including KT66
> and KT88 pentode output tubes. Amperex ECC83 & ECC88 as well.
> Also recal that the last number of a CRT is the phosphor type (7 is
> blue with a yellow afterglow - best for slow signals like EKG).
>
> Speaking of insulating coatings I still have a bottle of corona dope
> and also glyptal. "Glyp it then ship it" we used to say. Fish paper
> insulation instead of craft paper. Litz wire....
>
> Oh those were the days....
>
> Bob Landman
>
> Sent from my iPhone
>
> On Feb 16, 2013, at 7:25 AM, Steven Creswick
> <[log in to unmask]>
> wrote:
>
> > Brian,
> >
> > Just like a fine wine, getting better!
> >
> > Steve C
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> > Sent: Saturday, February 16, 2013 2:17 AM
> > To: [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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