Re: New Vector monitor project progress : Yoke issues

On Thu, 14 Oct 1999 17:11:27 -0400, you wrote:

>The magnetic field is proportional to the current (in the yoke), and thus
>more windings in parallel is better because:
>
>1.) the voltage does not have to be pushed too high due to higher impedance
>and
>2.) Less heating in the coils.
>
>I'm mostly looking for a technical dicsussion on this.
>Thanks for the comments,

Ok, technically, you are still going to have a problem with the speed
of your trace. You still have multiple coils acting similar to
capacitors (for completely different reasons) in their ability to
store a charge.

By placing them in parallel you have lowered the voltages needed to
quickly slew to different positions on the screen, but on the other
hand you have proportionally raised the currents needed to do the
same. (Ohm's law). If adding paralleled coils were a "win win"
situation, this surely would have been done by the original designers
saving themselves much grief. Instead, the higher speed monitors all
had less windings on their yokes, leading to higher stresses on the
drive electronics. Placing additional, paralleled coils, will only
increase these stresses. You will need higher current driving
transistors.

Previous searches for replacement transistors have shown that there
are not many around with the higher drive currents you will need. You
will probably have to place lower powered transistors in parallel to
get the instantaneous currents you will need for high speed
deflections.

This will also put a higher strain on your low voltage power supplies.
The internal resistance of the supplies will also need to be lowered
to deal with the instantaneous current spikes needed. Chances are
very good you will also need to double up on pass transistors there.

Everything's doable, but costs do add up.

I was serious about buying these. $250 is a deal! That's only $50
bucks above the price of a raster monitor. I'm not even sure you
could get a deflection board for that. I *know* you couldn't get a
new HV transformer! Hell, it be worth buying your kit just to rip out
the HV sections of my current monitors and use yours!

You can keep this at a technical level if you want, but you need to
consider costs very carefully before quoting prices, and there are
people on this list who have experience in putting together kits, and
all the costs involved. The multi-kits and the LV2000 come
immediately to mind.

Clay sold his original Tempest multikits for $75 (special pre-order
deals), I believe they're like $99 now. These are very simple (read:
all digital/no analog -- I don't want to start a flame war here! ;^)
designs with parts that are lower in price than what you will be
needing. From as much as I can tell, he's not planning on retiring by
selling these things, my guess is that when you add up the labor
costs, he's barely breaking even. (If I ever find out otherwise I can
guarantee you Clay's going to have some mighty strong competition!
;^)

-Zonn
Received on Thu Oct 14 17:23:27 1999