12-04-2021, 03:06 PM
Hi.
The saga is now over. Yesterday I got my 7BP7 back after many years. It was the basis of a CRT for testing the Pye. Once fitted there still the issue of way out frame speed. This tuned out to be a new 0.022uf cap reading 700pf!!! Once this was fitted we have the correct frame speed and locked as well.
The issue though is bad focus, the voltage across the focus coil is correct but the focus is not good.
I think its due to the parameters of the radar CRT requiring a different magnetic flux for good focus, any time I've used these tubes for tests the with a permanent magnet focus the control is in a totally different position.
The set has been running for a couple of hours now with so far no further problems. It will be run tomorrow all day for a soak test.
https://youtu.be/K-LV9iKEZPI
The saga is now over. Yesterday I got my 7BP7 back after many years. It was the basis of a CRT for testing the Pye. Once fitted there still the issue of way out frame speed. This tuned out to be a new 0.022uf cap reading 700pf!!! Once this was fitted we have the correct frame speed and locked as well.
The issue though is bad focus, the voltage across the focus coil is correct but the focus is not good.
I think its due to the parameters of the radar CRT requiring a different magnetic flux for good focus, any time I've used these tubes for tests the with a permanent magnet focus the control is in a totally different position.
The set has been running for a couple of hours now with so far no further problems. It will be run tomorrow all day for a soak test.
https://youtu.be/K-LV9iKEZPI
