1. Home
  2. ⏚ Electrical Engineering
  3. Crystal frequency for monochrome video signal?

Crystal frequency for monochrome video signal?

80's vintage German printing equipment (offset press industry) uses a video plug-in card (made by the manufacturer of this equipment) to generate parameter display for the operator. The display is a standard baseband video tube monitor. (It is possible, being German and sold in the USA market, that the video may be NTSC or PAL.)

There is no video signal on the BNC output connector.

This is used equipment being resurrected, so operational history is unknown.

There is a place on the video card labeled "Q2" that is the right shape & size for a crystal can. The pads look like it was ripped off the board: a short lead soldered in one pad; a hole in the other pad where a lead was soldered (poorly, apparently!). (Rough handling is a distinct possibility: the client is a used-equipment dealer and the fork lift is their main tool...).

The board is populated with 80's technology, mainly 74LS' :: the crystal pads connect to an 'LS04 inverter/driver and then to an 'LS96 parallel-to-serial converter. The 'LS96 spec sheet says that it can be driver up to 25 MHz.

The board uses a 8275 CRT controller, and in the datasheet it says: "CCLK is a multiple of the dot clock and an input to the 8275."

Maybe these clues will tell someone what frequency this crystal needs to be...?

What frequency crystal should I be looking for?

Thanks.

Reply to
DaveC
Loading thread data ...

Put in ANY frequency, as long as it is known. Fire the gear up, and observe the video output with a scope. measure the horizontal sync frequency. Now, you can easily figure the ratio (up or down) to get the desired H sweep freq, and most simple monitors should sync to it, even if the number of vertical lines is a bit off.

Jon

Reply to
Jon Elson

For that I'd need to know what the H sync is supposed to be.

What is it?

For that matter, how about a sig gen? Can this be 5v amplitude? Or microvolt?

Reply to
DaveC

This gets my vote.

If you have a guess at the number of horizontal pixels, get something close to line rate * pixels * 1.25. It'll still be wrong, but it'll be the best chance at getting the oscillator up and running.

Reply to
Tim Wescott

or get some scope with video lines countable, to find out 525 or 625 system ... the rest is in google, or folks in this group

:-)))

Reply to
halong

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.