29-10-2021, 05:42 PM
Hi.
Today I removed the choke on the anode and made a tunable RF transformer for the output. This greatly increased the signal output and improved stability. The lash up on the G2 has now been improved which now has improved the starting reliability of the oscillator. The G2 choke is now 470uh which gives optimum results. I then tested this on the Sony TV9-90 and aslo on a Philips TVette, there was still some hooking on the top of the picture. Looking at the envelope it showed signs of sync crushing so I tried out returning the ground of the video source to filament + this cleared up the hooking and the sync was just about perfect, moving the ground to the battery side of the filament dropping resistor improved it with some reserve. This has given G1a a little positive bias, as the grid is very high impedance with a 1m bias resistor to filament - no harm will happen to the source, an AC coupled video source though could be an issue so I'll investigate if this is going to be an issue.
The results are excellent, I've also tested this on my Pye V4 and the TV24C, Signal strength is actually way higher than the Aurora or Hedghog, I needed 48db of attenuation on the TVette before a hint of snow.
I'll update with a video shot earlier later on.
Today I removed the choke on the anode and made a tunable RF transformer for the output. This greatly increased the signal output and improved stability. The lash up on the G2 has now been improved which now has improved the starting reliability of the oscillator. The G2 choke is now 470uh which gives optimum results. I then tested this on the Sony TV9-90 and aslo on a Philips TVette, there was still some hooking on the top of the picture. Looking at the envelope it showed signs of sync crushing so I tried out returning the ground of the video source to filament + this cleared up the hooking and the sync was just about perfect, moving the ground to the battery side of the filament dropping resistor improved it with some reserve. This has given G1a a little positive bias, as the grid is very high impedance with a 1m bias resistor to filament - no harm will happen to the source, an AC coupled video source though could be an issue so I'll investigate if this is going to be an issue.
The results are excellent, I've also tested this on my Pye V4 and the TV24C, Signal strength is actually way higher than the Aurora or Hedghog, I needed 48db of attenuation on the TVette before a hint of snow.
I'll update with a video shot earlier later on.
