Re: New vector monitor design.

At 01:41 AM 5/28/97 EDT, you wrote:
>On Tue, 27 May 97 19:13 PDT Zonn <zonn@concentric.net> writes:
>>At 06:12 PM 5/27/97 -0700, you wrote:
>>>re: audio amplifiers for deflection amplifiers
>>>
>>>
>>>don't deflection amps have to be DC-coupled?
>>
>>Yes. You have to use modules that are powered from a split supply so
>that
>>they can be direct couple to the yoke.
>>
>>The module Clay was talking about can be run this way. I once owned a
>>Pioneer receiver that used STK-0080s that were DC coupled to the
>speakers,
>>with a switchable capacitor on the input to guard against any DC offsets
>>generated by any auxilary equipment.
>
>Although using consumer type parts is a great idea IMHO (cheap &
>relatively indestructible), I wondered if using industrial type power
>opamps might work.
>
>Can you say "engineering samples"? :)
>
>Lastly, since Zonn has worked out the deflection and HV issues, that just
>leaves how
>we get the RGB data to the guns. I assume we are going to reuse the neck
>board of
>whatever monitor/TV we choose to mangle and just bypass all the NTSC/sync
>circuits. Or am I missing something really important (again)?

I had planned on tossing everything on the neck board (except the socket!)
and use the drivers on the Amplifone deflection board -- I would use the gun
voltages on the neck board, bring it down to the Amplifone drivers. Driving
the RGB guns is probably the easiest part of the whole deal. These are
usually driven to ground with open collector transistor. The closer to
ground, the brighter the trace.

I say usually because I was looking at the schematic to a battery powered
O'scope last night and they had a unique way of driving the very small
display. They grounded the anode of the tube -- where the HV lead normally
goes, and then drive the guns with -800 volts. Strange and it also led to
some bizarre capacitive coupling to keep the standard 5v section isolated
from the -800 volt section.

If the transistors on the Amplifone can't handle the higher voltages, they
could possibly be replaced with the ones on the neck board of the TV.

Of course other arrangements are possible (varying voltages on blocking
grids), the key point is I wouldn't even start a conversion without a
schematic, which can be a bitch to get in consumer products. Hopefully
there will be a Sams photofact available.

Back to the Yoke/Flyback arrangement. It occurred to me that the yoke could
be replaced with a similar size inductor, or even smaller as long as the
tuning capacitor is adjusted accordingly. This would allow the flyback
oscillator to continue oscillating, and generating the HV. Hand winding an
inductor isn't that difficult (anybody ever wind their own crossover L-C's
for their homemade speaker cabinets?) Or better yet just find a yoke off of
another sacrificial raster monitor, I bet it would be close enough. It
wouldn't have to be very accurate, since I don't really care if the
oscillator continues to oscillate at the 15.75khz raster frequency. I just
need the HV at any filterable frequency.

That would allow the use of the TV's yoke.

-Zonn
Received on Wed May 28 10:05:58 1997