NBTV Scope Evolution
Posted: Sun Jun 07, 2015 12:28 pm
About 10 years ago i made a nbtv monitor scope with my trio scope ,one of those things where i never drew a schematic been thinking how i did this back then in an afternoon and it worked ,it was as i recall pretty simple i used a TTL monostable for the sync dectection could of been a 74121 or 123 for the horizontal sync had 2 555 oscillators the 400hz line sync synced the line 555 , frame used a 555 was free running and one transistor for the video ...here i recall i used a transformer backwards with one lead of the secondary conected to the collector other to the power supply this isolated the circuit from the HV of the CRT and gave enough voltage to change the intensity ....Thinking about the transformer i am vague about what i used it was either a mains transformer would have to low a bandwidth to work thinking about it now ,it was more than likly a Audio transformer would have enough bandwidth to produce a picture ...
Results were good did have picture roll as the framing was manual control..but it was pretty simple .
There are a few scope circuits out there but its more fun to try and make your own than copy all the time .....heres a different idea i have been thinking about ...
I know i can use a 4060 to output both the line and frame frequencies but i would need to sync this clock to the incoming line frequency if possible easier to use a crystal but i suppose a R/C clock would be possible to depends if i can find the right crystal.... have it i hope in with the rest of my crystals ..so thinking about this in the drawing using a bistable so the line controls the 4060 via reset ,not sure if this would work ? ...i more than likly need a sync seperator before the 555 bistable but this is the basic first idea at the moment for syncing and getting both line and frame frequencies for the ramp generators they could be 555s as well.
Could sync another way via the 555 ramp generators via pin 5 that might work too ...
The video side i need to look into what scope i have does what before working any thing out here .
Results were good did have picture roll as the framing was manual control..but it was pretty simple .
There are a few scope circuits out there but its more fun to try and make your own than copy all the time .....heres a different idea i have been thinking about ...
I know i can use a 4060 to output both the line and frame frequencies but i would need to sync this clock to the incoming line frequency if possible easier to use a crystal but i suppose a R/C clock would be possible to depends if i can find the right crystal.... have it i hope in with the rest of my crystals ..so thinking about this in the drawing using a bistable so the line controls the 4060 via reset ,not sure if this would work ? ...i more than likly need a sync seperator before the 555 bistable but this is the basic first idea at the moment for syncing and getting both line and frame frequencies for the ramp generators they could be 555s as well.
Could sync another way via the 555 ramp generators via pin 5 that might work too ...
The video side i need to look into what scope i have does what before working any thing out here .