At least it's just monochrome. NTSC composite video with color is rather complex, though I must say it is also ingenious in that it is backward-compatible to monochrome and packs so much video information into a 3.58Mhz bandwidth. Similar for PAL, though higher bandwidth.
On Sunday, April 11, 2021 at 4:19:20 PM UTC-7 artgod...@googlemail.com wrote: > It sounds a bit of a stretch - 15kHz to 19kHz. You could try running the > monitor without an input signal and adjusting horizontal frequency (if > there is one) to see what range it can manage. > > Another possibility is to fix it in software by creating a custom monitor > signal. Some information is at > > https://github.com/raspberrypi/documentation/blob/master/configuration/config-txt/video.md > > > > On Sun, Apr 11, 2021 at 10:51 PM jb-electronics <webm...@jb-electronics.de> > wrote: > >> 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) >>> >>> 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 . >>>> >>>> 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 >>>> >>>> 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 >>>> >>>> But I know there are also dedicated chips, like the GS1881: >>>> >>>> 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 >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "neonixie-l" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to neonixie-l+...@googlegroups.com. >>>> To view this discussion on the web, visit >>>> https://groups.google.com/d/msgid/neonixie-l/e0f398e8-24b1-952c-c998-0ddfbed6849e%40jb-electronics.de >>>> . >>>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "neonixie-l" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to neonixie-l+...@googlegroups.com. >>> >>> To view this discussion on the web, visit >>> https://groups.google.com/d/msgid/neonixie-l/CALiMYrvHCiXd3QSDmEJ%2Bpe3XgUutOC_C3yLFGxeOEo2bjtEAWw%40mail.gmail.com >>> >>> <https://groups.google.com/d/msgid/neonixie-l/CALiMYrvHCiXd3QSDmEJ%2Bpe3XgUutOC_C3yLFGxeOEo2bjtEAWw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >>> >>> -- >> You received this message because you are subscribed to the Google Groups >> "neonixie-l" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to neonixie-l+...@googlegroups.com. >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/a3fe30c7-c778-444a-a745-b6f6b1910bb1n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/a3fe30c7-c778-444a-a745-b6f6b1910bb1n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "neonixie-l" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to neonixie-l+...@googlegroups.com. >> > To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/37bf74f3-842f-2d17-c5b7-0606f09d9d4e%40jb-electronics.de >> >> <https://groups.google.com/d/msgid/neonixie-l/37bf74f3-842f-2d17-c5b7-0606f09d9d4e%40jb-electronics.de?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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