A poltergeist in my machine?

Jon Elson elson at pico-systems.com
Tue Sep 8 11:21:55 CDT 2015

On 09/08/2015 05:53 AM, Noel Chiappa wrote:
> My current best guess, after sleeping on it, relates to the fact that the
> 'magic' pin was an output from a delay line. Delay lines, in that era, were
> apparently potted confections of inductors and capacitors. So maybe the extra
> current drain with the probe on somehow affected one (or more) of the
> capacitors in the delay line? A total WAG, but it's very mysterious!
Most potted delay lines are made the same way.  You take a 
piece of aluminum foil-coated paper and roll it into a 
tube.  You then wind extremely fine magnet wire onto the 
tube.  The foil is a ground plane, and one of the 
distributed capacitor plates.  The wire is the distributed 
inductor and the other capacitor "plate".  This technology 
was used in the first color TVs, and I think pretty much 
everybody used the same technology for digital delays.

Well, it could be the delay line is going bad.


More information about the cctech mailing list