[Elecraft] Notes to new K2 builders - Part 1

Fri Mar 12 10:21:00 2004

Hi

  ----- Original Message -----=20
  From: Bill Tippett<mailto:[email protected]>=20
  To: [email protected]<mailto:[email protected]>=20
  Sent: Friday, March 12, 2004 8:19 AM
  Subject: [Elecraft] Notes to new K2 builders - Part 1

  I've completed the Control Board for #4119 and
  noticed the following:

  1.  I ended up with an extra 1N5817 diode, which is
  supposedly D3, but page 15 says to install R22 (82k)
  in its place.  Maybe R22 is installed for temporary
  testing so I'll keep the D3 diode until after alignment.

  D3 is replaced with the 82k resistor as part of the key click mod now =
included in all new K2's

  -------------------------------------

  2.  U1 is specified as NE602 or SA602 on page 19, but
  the IC in my kit was SA612...hopefully equivalent.

  Yes they are equivalent at HF frequencies

  ------------------------------------

  3.  Just a couple of thoughts on ESD protection.  Radio
  Shack has an ESD wrist strap for $4.95, and 5" X 5"
  conductive foam pads for $1.29.  I borrowed a large flat
  aluminum cookie sheet from my wife for a work surface,
  connect it to earth ground, place two pads on the sheet
  and clip my wrist strap to the aluminum sheet.  I always
  make sure I'm grounded before handling any device, such
  as transferring loose transistors from the kit bags.  Hopefully
  no zaps since my soldering iron is supposedly ESD safe.

  You should not work on a metal surface that is hard grounded. All ESD =
protection should connect to ground through a high value resistor of =
around 1 meg ohm or so. Having a grounded work bench is about the same =
as standing in a bathtub of water. It could be dangerous if some =
equipment failed and became electrically hot. The 1 meg resistor will =
protect you if this happens. Wrist straps usually come with this =
resistor built in.=20

  I also do not like metal work surfaces because of the possibility of =
shorts when working on disassembled equipment. If the pads you are using =
are the black foam used for IC's then I would not use them for a work =
surface because as they wear the foam disintegrates and little bits of =
the conductive foam will get into places and cause shorts. If you want a =
soft surface a clean shop towel or a cloth top mouse pad works well. You =
can lightly mist the surface with anti static fabric spray or wipe the =
area with a fresh drier sheet to improve the static resistance. The best =
solution is a commercially made antistatic work pad with the ground wire =
and the 1 meg resistor. These are about 1/8 inch thick foam with a tough =
anti static vinyl top coating and are about 2x3 feet. The top is not =
conductive enough to short out circuit boards placed on the mat but will =
still dissipate a static charge. Unfortunately they are expensive, but =
you may be able to find one on the surplus market or a used one with =
some life left at a swap meet

  Don Brown
  KD5NDB
  ---------------------------------

  73,  Bill  W4ZV

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