Thank you! I think it should be possible to modify the horizontal and
vertical deflection circuitry on the board to make it a proper NTSC
frequency, yes?
Jens
On 2021-04-10 10:52 p.m., 5-ht wrote:
Jens,
The horizontal sync requirement of this monitor (52 uS / 19.2Khz) is
somewhat higher than a standard NTSC signal which is about 63 uS /
15.7 Khz.
Mark
On Saturday, April 10, 2021 at 8:04:15 AM UTC-5 Jens Boos wrote:
Thank you! I did some more digging and found the service manual
for the display (Panasonic TR-60S1A, see here:
https://www.opweb.de/english/company/Panasonic/TR-60S1A
<https://www.opweb.de/english/company/Panasonic/TR-60S1A>)
There is is a timing chart (see below). It looks an awful lot
alike NTSC to me, can somebody confirm?
Best wishes
Jens
On 2021-04-10 12:28 a.m., Adrian Godwin wrote:
It's easy enough to extract the sync signals, as you've seen. It
may not be particularly difficult to modify the TTL input to
analog, or to create a TTL level signal if you don't need a
grey-scale. On many general-purpose monitors like that they
could often be built for either standard - the microvitec Cub
popular with the BBC Microcomputer had that option.
But the critical thing is that it runs at the right speed. CRT
circuits are built around the line oscillator which generates the
horizontal scan AND the EHT voltage. It was only when multisync
monitors came along that the optimisation was split to reduce the
dependency. And if the frame frequency is wrong, you will often
have problems getting a full frame scan when you force it into sync.
So the first thing is that you need to make sure the 8920 monitor
ran at either PAL or NTSC rates so you can choose a raspberry pi
format to match. There's a good chance it's NTSC but later
monitors like the ones in the 54 series of digital scopes were
more like the IBM standards MDA and EGA (CGA was NTSC).
On Sat, Apr 10, 2021 at 4:28 AM jb-electronics
<webm...@jb-electronics.de> wrote:
Hi all,
This is a bit of an off-topic question, but I hope there will be
somebody here that can help. I have bought a new-old stock
monochrome
CRT for a HP Agilent 8920A, basically this unit here:
https://www.ebay.com/itm/273930914548
<https://www.ebay.com/itm/273930914548> .
It looks to me that it is just a rebranded OmniVision 6"
display:
http://www.omnivisionusa.com/Industrial-LCD-CRT-Monitors/replacement-crt/crt-monitors/6-inch-kit-.html
<http://www.omnivisionusa.com/Industrial-LCD-CRT-Monitors/replacement-crt/crt-monitors/6-inch-kit-.html>
Now unfortunately it takes TTL video as input. But I have a
composite
source (a Raspberry Pi). How can I convert composite into TTL? I
basically need to extract Hsync and Vsync and feed it
separately to the
unit, okay. There is an old circuit here that does just that:
https://www.elektormagazine.com/magazine/elektor-198812/47485
<https://www.elektormagazine.com/magazine/elektor-198812/47485>
But I know there are also dedicated chips, like the GS1881:
https://www.mouser.com/datasheet/2/761/GS1881_GS4881_GS4981_Datasheet-769183.pdf
<https://www.mouser.com/datasheet/2/761/GS1881_GS4881_GS4981_Datasheet-769183.pdf>
So basically here is my question: before I dive into this any
further,
is there any chance of success? What is the optimal choice?
Or is it
quite unlikely that I will be able to convert the signals? I
mean, even
if I manage to extract Hsync and Vsync, is it likely to work?
I am sorry for the naive question, but I am no expert on
video signals,
and it would be nice if anybody more experienced could chime
in with a
few words of caution/experience.
Best wishes
Jens
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