Steve Anderson wrote:In general you should be able to adapt all of the 3BP1 circuits to the VCR139A, it's much the same as any CRT from that era. You just need to adjust some voltages here and there, I'm confident you can do that, but if you get stuck...well, you know where others and I are...
Thanks Steve thats good that makes it much easier i have a good idea what to do now and how most it still went and what not to do ...this time i will have it well grounded for a start .
I am more confident Steve on this one apart from changes on how well it will work but most of it should go a lot easier than last time.
Yes, the opto-isolator should be good for up to a few hundred kHz, beyond that, say 405/525/625, a faster device would be required. Though on a 3" screen it's doubtful if you would see any difference. !20/128 lines (SSTV) is about the limit on a 3" screen. Even at 72 lines as I did a few years back, the lines are starting to merge with each other.
Steve A.
Much better to go with this design i have a few of the same opto couplers...
I was thinking the thing will have to be well focused for the higher line rates yes i can see these small tubes have there limits even so useful to learn and i want one is my excuse