[Boatanchors] Cordwood modules (was: Re: [Glowbugs] SPOTTED: GONSET G-76)

Michael A. Bittner mmab at cox.net
Tue Feb 28 20:20:11 EST 2012

Besides the stacked modules used in Motorola portable radios (One with a socket for the 1R5 converter and one with a socket for the 1U5 detector/1st audio amplifier.), perhaps you are referring to the "cordwood modules" used in ICBM electronics of the time.  Mike, W6MAB
  ----- Original Message ----- 
  From: Brad Thompson 
  To: Brian Carling AF4K 
  Cc: boatanchors at puck.nether.net ; dcboatanchors at mailman.qth.net ; tetrode at googlegroups.com ; glowbugsmailinglist at yahoogroups.com 
  Sent: Tuesday, February 28, 2012 5:02 PM
  Subject: Cordwood modules (was: Re: [Glowbugs] SPOTTED: GONSET G-76)

  On 2/28/2012 7:34 PM, Bry Carling wrote:
  > Ah "hybrid modules" - the bane of the 1970s! A lot of companies used
  > those in organs and other gadgets I serviced back then. Those secret,
  > "Giant Integrated Circuits" before the tiny DIPs on 0.1" centres were
  > invented, or in widespread use. If one died you were almost dead in the
  > water. Seems like Lowrey used them. Maybe for oscillators or keying
  > switches.

  Hello, Bry--

  Are you referring to modules that resembled stacks of very small
  Saltines (tm) with interconnecting wires running vertically along the
  edges? IIRC, Motorola used these in some of its consumer electronics--
  namely, AM BC-band portable radios.

  This concept was developed as "Project Tinkertoy" at NIST (nee NBS):


  Motorola also marketed its printed-circuit based products as built
  using "Pla-cir" technology (there's an accent bar over the "a", making 
  it sound like the long a in 'play'). The boards were double-sided and
  not too reliable.

  > I worked as a test engineer for a company that used PHILBRICKS in some
  > pretty fine signal recovery equipment in the very early 1970s, and they
  > also made their own "ICs" using two pieces of PC board spaced about 1"
  > apart with vertical wires and parts in between them, to form a cube of
  > components. Tricky stuff. Once they potted those things you were left to
  > your imagination to figure out the differential amplifiers, comparators,
  > summing amplifiers and other mystery circuits inside! Give me tubes any day!

  That's "cordwood" packaging-- compact, rigid when potted and nearly 
  impossible to repair (before potting)if a component failed in the middle 
  of the stack. You'd have to remove good components to reach the

  One ad slogan of the times stated that "Our modules are potted in
  Timonium"-- meaning the assembly plant was located in Timonium, MD.
  The first time that I saw the ad, I wondered what kind of everlasting
  epoxy they used.<g>

  One thing about epoxy potting-- it covered up a multitude of of
  construction flaws.


  Brad  AA1IP

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