Passive Cathode ray tube modulation
Posted: Sun Oct 28, 2018 7:21 pm
Well i needed my little trio scope to do some z axis modulation to test some video file's out and see how accurate the FSC clock sawtooth circuits are ,and what i thought was the problem on the scope a 10nf 2kv cap seems fine as well as all resistors so i just left it after replacing the capacitor and recalled something i did 2 decade's ago and thought i would try and see if my vague memory of it was correct .
So the procedure after the schematic is brake the connection for the cathode pin 3 and connect a spare mains transformers primary between that and pin 22 rest explained below schematic .
Pretty much a very simple idea i don't know if it has been used in the past by any one else ,pretty much the idea was and is just using a small mains transformer the primary 240 volt side is used between the cathode and its negative 1500 volt supply ...so only 2 connections .
The secondary which i think would of been 12 volts side is used for the modulation input just connected right from the lap top to ground and signal output connection just another 2 connections to that secondary .
So small signal about a 1 volt or so at best can modulation your scope if you don't have a Z axis connection .
It does rely on how high the video level is but every thing i tried seemed to work some files better than others but had not used any thing apart from this passive induction amplifier .
A speaker audio transformer i think would also work more than likely ,i was surprised it still worked without the one transistor amplifier i also recalled i used back then .
So results below upside down and reversed ...least its not inverted I will add a video amplifier transistor to this but for using a little transformer and 4 connections a quick and dirty z axis modulation .
So the procedure after the schematic is brake the connection for the cathode pin 3 and connect a spare mains transformers primary between that and pin 22 rest explained below schematic .
Pretty much a very simple idea i don't know if it has been used in the past by any one else ,pretty much the idea was and is just using a small mains transformer the primary 240 volt side is used between the cathode and its negative 1500 volt supply ...so only 2 connections .
The secondary which i think would of been 12 volts side is used for the modulation input just connected right from the lap top to ground and signal output connection just another 2 connections to that secondary .
So small signal about a 1 volt or so at best can modulation your scope if you don't have a Z axis connection .
It does rely on how high the video level is but every thing i tried seemed to work some files better than others but had not used any thing apart from this passive induction amplifier .
A speaker audio transformer i think would also work more than likely ,i was surprised it still worked without the one transistor amplifier i also recalled i used back then .
So results below upside down and reversed ...least its not inverted I will add a video amplifier transistor to this but for using a little transformer and 4 connections a quick and dirty z axis modulation .