New Vector Monitor Project: Deflection I & V Measurments

Ok, I just measured I & V on Tempest: Here is the data:

Procedure:

10X scope probe used, X&Y measurements are at output with respect to ground,
so they are off by about 2 volts due to Voltage drop across the shunt
resistors. Current measurements taken by measuring voltage across 1.5 Ohm
shunt resistors with scope. 2 Volts typ peak across 1.5 Ohms, 4Volts Max.

Data:

Voltages X&Y approximately +/- 25V peaks
Current: typical peaks about +/- 1.3 Amps
Current: Max peaks about +/- 2.6 Amps

Conclusions:

Without a precise RMS measurement, I'm going to estimate a typical RMS Power
output of
about 25 Watts.
Peak Instantaneous Power output was 65 Watts.

The LM3886 can do 68 watts continuous into a 4 Ohm load and 135 watts peak.
To compare these numbers directly, one would need to know the impedance of
the yoke at the frequencies used (approx. audio up to 100 kHz) So far, it
still looks like it might be a good match to me, and worth testing out.

Comments Graciously Requested

James

----- Original Message -----
From: James Nelson <nelsonjjjj@didactics.com>
To: <vectorlist@lists.cc.utexas.edu>
Sent: Friday, November 05, 1999 8:12 AM
Subject: Re: New Vector Monitor Project: LM3886

> Rodger, you're not raining on a parade at all, and don't stop criticizing
> designs, otherwise I won't get something that works.
>
> The specs on the LM3886 looked ok to me, but maybe it's time for me to do
> some actual current and voltage waveform measurements on Tempest to see if
> it's too demanding for the use of such a device or not. I don't think
that
> we are running over 50 watts of power through the yoke.
>
> I'll let you know what I come up with on those measurements!
>
> Thanks,
> James
>
>
> ----- Original Message -----
> From: Rodger Boots <rlboots@cedar-rapids.net>
> To: <vectorlist@lists.cc.utexas.edu>
> Sent: Friday, November 05, 1999 1:53 AM
> Subject: Re: New Vector Monitor Project: Microprocessor, etc...
>
>
> > James Nelson wrote:
> >
> > > I'm looking carefully at the National LM3886 Power OP AMP for direct
> yoke
> > > drive, and it doesn't cost the $100+ each like some of the other
<choke>
> > > cool ones do, and it has all kinds of protection circuitry, and Class
AB
> > > circuitry.
> > >
> > > Rodger is going to look at the LM3886 to see what complaints he might
> have
> > > with the device, and I might throw up a proposed 1st order schematic
for
> > > that circuit soon.
> >
> > Well, I've looked at it and have some serious questions if it has the
raw
> balls
> > needed for a color vector monitor. B&W, maybe, but I think it's going
to
> keep
> > shutting down running color, even with massive cooling. Especially on
> games
> > that overscan the monitor.
> >
> > Yeah, shutting down will protect the IC, but how many times can you
> collapse the
> > sweep on a game before you burn a big cross in the middle of the CRT.
> We're not
> > talking losing one half of a screen here, we're talking collapsing into
a
> line.
> > Or worse yet, a dot if both channels dump at the same time. The spot
> killer had
> > better be damn fast.
> >
> > I hate to keep raining on this parade so would someone please tell me
I'm
> full
> > of it (and be ready and able to prove it!) already?
> >
> >
>
>
Received on Fri Nov 5 09:14:24 1999