Gordon Couger wrote:

> From time to time I have thought soft x-rays should erase OTP chips.

  The concept has merit.

> Has anyone tried it.

  I haven't yet.

> A soft x-ray source can be made from a vacuum tube.

  Ah, now we're getting a bit into science fiction!  By the time you set
up a manufacturing facility to re-construct your "vacuum tube" into an
X-ray tube, it is hardly a backyard enterprise.

  An X-ray tube consists of an electron gun similar to that in a CRT
(TV, oscilloscope) *except* that it generates from five (dental, II) to
200 times the beam current, focussed onto an oblique tungsten anode such
that all the X-rays come out *in one direction*.  The problem with
X-ray emission from TV tubes and the old EHT shunt regulators is that it
comes out *all over the place*!

> If any one thinks it is sound I can probably set up a trial.

  Have I made my point?

  Let me give you a suggestion.  If you want to try it with your
dentist, use the absolute *lowest* anode voltage to which the machine
can be set.  Whenever this discussion comes up, people start talking
about using industrial x-ray machines and the like, set up for
ridiculously high anode voltages.  It seems not to be intuitive to them
that "hard" X-rays which simply travel straight through the plastic
package, silicon die, object holding the chip, the table, the floor and
just keep on going have *no* effect erasing a chip!

  Cheers,
        Paul B.