RE: TED based motherboard

From: J Ellsworth (
Date: 2007-03-29 00:51:06

"Ah…. I know what this is.  I did this board through Fourth Generation, a
local PCB design house.  That’s my writing on the labels as well as the P19
on the board.  The processor was hand bonded (little old ladies with
microscopes) and the lid taped on.  Probably not working as I imagine the
passivation was missing or bad.

This is one of the boards we gave developers to produce TED type software on
before the release, since TED wasn’t C64 compatible they needed something to
get started on before the real product hit the shelves.  The joystick
connectors matched what developers would have had for joysticks (Atari
style).  How did it get to Sweden?  We sent it there through Sig Hartman’s
Software/Games group most likely  The odds are that this is a PAL version
though we were probably sending out monitors also to support NTSC so it
could go either way.


"So short answer, this is one of mine, it was to get the core chip set out
as early as possible."

BTW, the gentleman that was asking about fixing this should be able to fix
it by talking the processor, TED chip, etc out of any working TED family
product.  Probably easiest way is to test the power supplies (two fuses, two
sources) and then swap chips.

Weird to see my handwriting from when I was 24  years old, 24 years later."

"Reading backwards, someone asked about the resistors vs the diodes.  I did
switch to diodes as the whole goal was prevent the hi-z input from getting
above VCC which would trip the test mode (if it sounds squirrelly, it sort
of was).  I proved that the problem was that they weren’t effectively
terminating the pins inside the chip by adding pull-ups which lower the
impedance basically to the value of the resistor.  Diodes are lower
impedance yet when forward biased, so these would have strapped these inputs
to one diode drop above VCC keeping them out of test mode in spite of the
strength of the interference field.  (You could do a moiré patter by holding
the board next to the monitor because the monitor interfered with the
graphics chip which in turn changed the monitor which in turn changed the
interference, etc. etc.)  They might even be germanium, it would be
interesting to see."

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