62 December 2017
READER - TO - READER TECHFORUM
VAX VMS Emulation
Is there an emulator for a Digital
Equipment Corporation’s VAX VMS
4. 7 machine, either running on an
SBC (Single Board Computer), or
possibly an image that can run as
a virtual machine in VMWare or
I want to create a four-node VAX
cluster like the one I used to work
on, and would love to see it sitting on
my desk as a stack of Raspberry Pi
#12171 Troy Thoele
Could someone explain in simple
terms how an AMP clamp works?
Does it have a transformer in it or
Hall-effect sensors or similar?
#12172 Kevin Champion
VGA To LCD
I would like to be able to drive
a 4x20 line LCD with a VGA output
from an old computer. Is there a
simple interface to do this?
#12173 Evan Lee
Solid-State Tube Replacement
I’m refurbishing a tube-type
Hallicrafters shortwave receiver. I was
planning on using a solid-state plug-in
replacement for the rectifier tube;
mostly because I can’t find the tube.
I’ve been told that a solid-state
rectifier could result in higher voltage,
and may blow the filter capacitors
and run the tubes at a non-linear
part of their operational curves. Can
someone confirm or explain if this is a
good idea or not?
#12174 Matthew Stiefel
[#9171 - September 2017]
What’s In A Board?
There are plenty of high quality,
double-sided printed prototyping
boards readily available on eBay.
They are perfect if used as they are,
unless — as it often happens — the
need arises to trim, grind, or otherwise
Here is my problem: I am deeply
concerned that these boards are made
with asbestos. I know that for any
grinding job a facial mask is a must,
but if the dust created in the process
could contain asbestos particles,
much stronger protection measures
would be warranted. Or, perhaps such
operations should be entirely avoided.
I imagine that many electronics
enthusiasts cut or even grind these
items, completely unaware of the
danger they may pose. I tried to gather
information from the Web about these
products, with little success.
I would like to know — preferably
from an authoritative source — what
materials are used in production
of these (mostly Chinese in origin)
#1 A “proper” printed circuit board
(PCB) is made from epoxy resin with
a fiberglass filler or from phenolic
resin with paper filler. Any of this stuff
would be better if you didn’t breathe
it, but it’s not asbestos. One way to
minimize the problem is to cut the
fiberglass board with tin snips. That
makes little to no dust.
#2 It’s unlikely you’ll find asbestos
in circuit board material. Most are
fiberglass and epoxy. Still, you don’t
want to breathe fiberglass dust when
you cut a board. A dust mask and
safety glasses work well to keep dust
out of lungs and eyes.
Most often I use a sharp box
cutter or an X-ACTO knife to score
the PCB and then snap the sections
apart. The knife doesn’t need to cut
all the way through a piece of board.
A small coping saw with a fine-tooth
blade would work too.
Also look at jeweler’s saws that
come with fine-tooth blades. You’ll
need a vise or a clamp to hold the
PCB steady for sawing.
[#9172 - September 2017]
Generators, Motors, And Other AC
I’m trying to make sense of
everything coiled, but the only thing
getting wound up is me! I thought I
knew a bit about electromagnetics,
but recently I’ve been trying to make
sense of all these fields and flows.
What is the difference between
the magnetic field and the flux?
How does flux work in a transformer
or a generator? Does anyone really
understand Maxwell’s Equations?
So many textbooks dealing with
electromagnetism speak in equations
instead of English. I want to know
HOW it all works, not just how to
compute these things. Am I just
reading the wrong books? Can you
help me figure out what the flux is
#1 I'm also struggling with
the same thing. I recently found
a series of great electricity and
magnetism lectures that are easy on
the math and have lots of practical
demonstrations on You Tube. These
are by Walter Lewin at MIT and you
can find them by searching for 8.02X
on You Tube.
The first lecture is at https://
SibwIPM4&t=478s . Also, there