Many start out with an Arduino uprocessor kit now.
The "basic" component has just bumped up in complexity a bit...
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Saturday, February 16, 2013 12:41 PM
To: [log in to unmask]
Subject: Re: [TN] AR/UR Conformal coatings - NTC
My word, you did a lot of construction work! The only rcvr I made was a
regenerative design (it howled when the regen pot wasn't set right but it
had incredible sensitivity for a one tube rcvr. The superheterodyne was
better of course but a lot more parts which I couldn't afford. (2.8 to 40
MHz)
The design came from the 1949 ARRL handbook (my prized possession) and used
a 6SN7. Wound the plug in coils (on those Bakelite forms). 80 rectifier in
the power supply. Wish I hadn't scrapped it. The input coupling capacitor
was two 1" square copper plates. One fixed, the other attached to a
plexiglas rod with two pieces of 12ga wire soldered to the plate then glued
into holes drilled in the rod. It was very sensitive - just a few pF seemed
to make quite a difference. Listened to a lot of shortwave radio from Europe
and even Radio Moscow (wonder if J. Edgar Hoover knew I did that :-)). Had
my radio "shack" under the stairs to the cellar. I think I was about 10
years old? Had to use magnetic earphones, of course, and not touch the
phone tips as one end had B+ on it! Got nailed a few times. A lot of fun.
I don't see how kids today can learn about electronics with everything going
to SMT. Its all about software these days....
Bob
Sent from my iPhone
On Feb 16, 2013, at 12:16 PM, Inge Hernefjord <[log in to unmask]>
wrote:
> 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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