Hi.
It was last December that I lashed up a 405 line Band 1 Channel 1 vision modulator. Where has the time gone?
After thinning down my collection and having decided that I am no longer repairing Vintage Radio & TV for others It's now possible to have some "me" time, like us all we are not getting any younger.
I've now rebuilt the vision stage onto copper laminate board and have tested it.
As before I'm using a 1ZH42B dual grid rod pentode, the HT is 80v and the filament is running 1.12v from an Ni-Mh AA battery via a 1ohm series resistor.
The video input is fed to one control grid via a 470Ω pot (set near max). The interesting thing is the result was a negative going picture. I didn't have this issue in December.......Then id came back to me that the grid needed to be driven positive between 0.7 & 1.0v, the result then flips positive.
The second grid has a crystal connected to it and the other end to the G2, which gets its HT via a 470μh choke, the second grid is bled to ground with a 1mΩ resistor.
There is more info on this video.
https://youtu.be/CXAPpi9cFYI