Re: The magic HV unit

On Fri, 12 Apr 2002 14:11:20 -0500, "Bachmann, Joe C" <joe.c.bachmann@xo.com>
wrote:

>MC1 is labeled as "Magnetic Correction 1", hence you would be right, this
>compensates for not having a yoke. But, if you read what I had to say about
>replacing this - with 3 10mh chokes - this may be a possibility in a new
>circuit.
>
>Overall, the amplfione HV unit is a very simple design that could most
>likely be adapted to any HV transformer.

It's not quite as simple as it looks. We used to use ferroresonant transformers
in some manufacturing equipment, our company (at the time) built. By placing a
transformer into resonance at 60hz, using a cap across one of its windings, the
transformer company was able to maintain a constant 120v output at any voltage
from 65v to 150v going in. It also maintained its output voltage under a
variety of loads.

I'm pretty sure the Amplifone regulator is working in a very similar way.
Notice there is no feedback for voltage regulation. The only feedback is the
over voltage cutoff circuit required by law. This cuts off the HV if it gets
above 25kv (and starts creating X-rays). It doesn't regulate the voltage.

If this is a ferroresonant circuit, the MC1 is not there to compensate for not
having a yoke, but to tune the circuit into resonance.

Outside of resonance you would still have HV presence, but it would not
regulate. The picture will bloom as more vectors are drawn. Things flashing on
the screen become rather irritating as the screen changes size in sync with the
flashing.

A real front end regulator is a lot easier to work with (similar to the WG HV
section), since it does not rely much on the specifications of the HV
transformer. And I'm sure it could be simplified, with better regulation, using
something like a 723 voltage regulator. This is what is done inside the Keltron
(Gold box) transformer used on newer Vectorbeam monitors. In fact if this
schematic is available, this might be a good place to look for circuit ideas.

>Now, I need some WG 7000 parts. The reason why I chose the 7000 is that Bob
>has the FBTs available at $21 ea.

I remember these parts being cheap, which is why I also thought they would be a
good place to start.

Good luck to ya!!

It'd sure be nice to redesign these monitors and a HV section is a great place
to start!

(Now if we can only get yokes wound...)

-Zonn
---------------------------------------------------------------------------
** To UNSUBSCRIBE from vectorlist, send a message with "UNSUBSCRIBE" in the
** message body to vectorlist-request@synthcom.com. Please direct other
** questions, comments, or problems to neil@synthcom.com.
Received on Fri Apr 12 13:45:31 2002