Old CRT video signals

ewlsey · Nov 4, 2017

I've got a 9" Omnivision CRT here. It works in my Yasnac controls that use TTL video signals. It uses a 10 pin edge connector.

I want to use it in a Dynapath control that uses composite video, also wit a 10 pin edge connector.

I hooked it up, but it doesn't work. Did they make 2 versions of the circuit, or is there a way to convert between the different systems? The manual seems unclear. On the TTL system, Pin 6 and Pin 9 are horizontal and vertical timing signals. Pin 8 is an intensity signal. On the composite system, Pin 8 is composite video, Pin 6 and Pin 9 are not used.

Does anyone know how this works? This is 30+ year old technology.

Here is the manual. This is not exact, but very close to my CRT. The chip sets are the same. http://oz1db.dk/hp/omnivision_man_lp06xx_rev0_0611.pdf

AlexO · Nov 4, 2017

ewlsey said:
I've got a 9" Omnivision CRT here. It works in my Yasnac controls that use TTL video signals. It uses a 10 pin edge connector.

I want to use it in a Dynapath control that uses composite video, also wit a 10 pin edge connector.

I hooked it up, but it doesn't work. Did they make 2 versions of the circuit, or is there a way to convert between the different systems? The manual seems unclear. On the TTL system, Pin 6 and Pin 9 are horizontal and vertical timing signals. Pin 8 is an intensity signal. On the composite system, Pin 8 is composite video, Pin 6 and Pin 9 are not used.

Does anyone know how this works? This is 30+ year old technology.

Here is the manual. This is not exact, but very close to my CRT. The chip sets are the same. http://oz1db.dk/hp/omnivision_man_lp06xx_rev0_0611.pdf

30 years is about last time I made a Spectrum Sinclair clone.

I forgot most of this stuff but I suggest you ask a question on eevblog :

EEVblog Electronics Community Forum - Index

Might be of interest but I believe there are a couple of kits to swap a crt for liquid crystal. They need that badly for old spectrum analyzers.

steve-l · Nov 4, 2017

There are multiple video signal formats with and without sync signals, analog and TTL. They are not interchangeable or compatible with each other. There used to be converters available. Google them.

rons · Nov 4, 2017

A composite video signal combines horizontal, vertical, etc. A monitor that accepts composite will decode the signal into the original component signals. It's possible to bypass the circuitry and connect the monitor with direct video. I have done it before for displaying a digital computer display signal on a ordinary television.

If you had the schematic of the composite input monitor then you bypass the composite decoding section.

Otherwise you need to combine the TTL signals. See page 102.

https://www.tinaja.com/ebooks/tvtcb.pdf

ewlsey · Nov 4, 2017

I guess I'm just confused why the manual shows TTL, composite, and VGA inputs, but only 1 circuit diagram.

Chip Chester · Nov 5, 2017

Just a guess, but maybe all the signals are distributed across the 10 connections, and you pick the interface to match your monitor by choosing the right connections and otherwise configuring the card. For example, composite only needs 1 signal pin, plus ground. Ground for composite theoretically should/could also be the same as ground for all the other video signals. The exist separately on connectors to make it easy to connect the cable shields where needed.

CGA monitor can get by with 7 connections (including ground).
VGA adds monitor ID info wires to the above 7 connections, but that could be set by switches, too, if your controller allows.

Chip

ewlsey · Nov 5, 2017

Appendix A and B are both CRT driver boards, the only difference is the ICs for horizontal and vertical. My CRT uses the later model chips.

rons · Nov 6, 2017

I got it backwards. Your CRT accepts direct video but the Dynapath outputs composite video. You need a circuit to decode a composite signal to direct video.

The composite signal is about 1 volt peak-to-peak and will have vertical and horizontal sync pulses which go from some intermediate voltage level to zero volts. The vertical syncs are a longer duration than the horizontal syncs.

The video information is in between the sync pulses and will have to be level shifted to TTL levels.

All that can be done. The Lancaster book explains what all this means.

composite video signal - Google Search

Search

Largest Manufacturing Technology Community on the Web

Search

Old CRT video signals

ewlsey

Diamond

AlexO

Banned

steve-l

Titanium

rons

Diamond

ewlsey

Diamond

Chip Chester

Diamond

ewlsey

Diamond

rons

Diamond

Similar threads