Re: Ampliphone HV-other options?!

----- Original Message -----
From: Zonn <zonn@zonn.com>
To: <vectorlist@mcfeeley.cc.utexas.edu>
Sent: Thursday, June 10, 1999 3:42 PM
Subject: Re: Ampliphone HV-other options?!

> On Thu, 10 Jun 1999 15:27:52 -0500, you wrote:
>
> >Look at http://randyfromm.com/techdept/ for those schematics.
>
> Well I just checked out the WG schematics (JPG!, uck!, and parts of
> the schematics are chopped off! Geeze!)
>
> Anyways we struck out there. The flybacks' primaries are designed for
> 123v. It looks like most all the raster monitors run of this voltage.

Yeah, almost all flybacks run off this (Except some AC/DC sets-some of those
have a 15 volt B+!!).... but no has mentioned this: there is a capacitor
wired from the collector of the H-out to GND on every H.V. system. This is
called a safty cap. It sets the speed of the discharge though the FB when
the transistor cuts off. Higher/larger value= LOWER High voltage= wider,
lower spike on the HOT. Lower/smaller values give more "Spike" to it
(higher/sharper), and generates more voltage...
  Maybe adjusting this will provide enough HV on a lower voltage B+?
If a certain cap value works at 120 volts in (with 30KV output) then if the
value is halved, 60 volts in would produce the same HV! (2X current in of
course!) The value is really critical- TV's use a 2-3% cap rated out to 4
decimal places like .0015 uf.
Getting 20 KV out of a t.v. transformer ran on 40-50 volts should be
possible!

> So maybe the deal is to design a HV supply using an isolation
> transformer, a 123v regulator (with error correction for adjusting the
> output HV), and both the Horizontal transformer and Flyback of a WG.

If the drive winding is isolated (either by winding it externally or by
internal design) no isolation Xformer is nessasary. In fact, most Flys have
a "Floating" drive winding, since the other end goes to the B+ supply-all
other windings go to ground.
The WG and AMP flybacks are the exceptions...
 Also, the High voltage itself sould be regulated; NOT the B+! High voltage
can vary 2-3 kv or more depending on screen brightness, causing blooming,
lines not meeting, etc. Big-screen sets DO directly sense/regulate the high
voltage, otherwise the picture would change size a lot (1-3 inches) with
brightness changes.

> I didn't check the G2 voltages, but they could probably be made
> usable, especially if they're too high. (Too low might be a problem!)

Both foucus and G2 will be low on a T.V. fly-since the out put is only 20KV
for vector monitors, not 30 KV as originally designed (wrong divider
ratios). Hopfully the controls will have enough range...

> It might be overkill, but it still might be cheaper than a single
> flyback from Wintron. And the parts will probably be available for a
> long time.

Agreed!
>
> -Zonn
>
>
Received on Thu Jun 10 22:32:40 1999