AncientBrit wrote:Hi Harry,
Ext.Sync is an alternative to using the Y signal to trigger the X axis timebase and allows the timebase to hard lock to say 525 or 625 mixed syncs.
Z axis or Z mod is a feed to brightness modulate the CRT tube and can go either to grid or cathode.
Can be used to brightness modulate a raster.
Normally the Z mod is fed internally from the timebase and used to blank the flyback portion of the X axis scan
So they are separate feeds.
Cheers,
Graham
Steve Anderson wrote:Clearly this guy didn't do much research into the subject and fumbled around until he got what he appears to have wanted. I suggest you delete that text.
'External Trigger' or 'External Sync' is precisely what it says it is, an external waveform triggers the internal timebase, without that trigger you have no trace unless the 'scope timebase is in 'Auto + External' mode where the timebase free-runs until it detects a external trigger signal.
[/quote]The Z input is a signal applied either to the grid circuit of the CRT (more positive - less negative) and makes the trace brighter, the converse if applied to the cathode. No different to CRT based TVs.
Steve A.
M3DVQ wrote:What I did on my scope driver is rather than have the counter triggering a pair of sawtooth generators which seemed awfully fiddly to make linear to this youngster from the digital age I constructed one long (I think 12 bits) synchronous counter clocked from the appropriate bit of the 4060. I connected the outputs up to a pair of DAC ladders, 5 bits for X and the rest for Y. I seem to recall I did some sort of synchronous load rather than a complete reset since I reset on the missing pulse so am always a fraction late. I believe the crystal was a 3.2768 MHz one since that divides down to the 12.5 Hz.
I assume that if you do missing sync detection for frame sync on yours you will get the video drawn slightly shifted up the first line unless you find a way to build in regeneration of the sync pulse from your counter if it doesn't get reset. I just have a small black region at the corner the length of time it takes the detector to realise the sync was missing.
I think I built a spot killer into the Z driver by just triggering another monostable off the sync separator, unfortunately since on my scope higher voltage = dimmer spot there's no protection if the power gets interrupted. That would certainly be a benefit of using the scope's own timebase circuits and feeding it an external trigger pulse but that's only much use for horizontally scanned systems.
Alas my schematics are all in pencil on tatty bits of paper somewhere folded up in the workshop somewhere. I've never been much good at writing up my experiments properly
The sweep generation's not very 'analogue' so not to everyone's taste but people seemed to like the image quality at the convention
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