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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
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DaveC Inscribed thus:

WAG 14.35Mhz possibly.

--
Best Regards: 
                        Baron.
Reply to
Baron

Also diode modulators.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)
Reply to
Fred Abse

Diode modulators didn't really catch on until the inline gun CRTs came along.

I've seen a saturable reactor a little more recently in the B+ regulator of an early multisync VGA monitor, the bias winding was driven by a TL431.

Without my early CTV experience I might've spent some time figuring out WTF was going on.

Reply to
Ian Field

Magnetic amplifiers are quite common in switch mode PSUs.

Hitachi/Metglas make a range of amorphous iron toroids specifically for that purpose, as do Ferroxcube, in ferrite.

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)
Reply to
Fred Abse

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