Pye B16 console TV restoration.

[Geordie McBoyne]

Circuit diagram of the frame timebase and the Pye "Positive Interlace Filter". The frame blocking oscillator transformer in my set was replaced before I acquired the set with a two windings component. I'm on the lookout for the correct transformer with the sync injection winding.
The ramp forming capacitor C22A has the unusually small value of 0.01mfd. The Frame timebase valve is a Mullard ECC34. A 6SN7GT doesn't work well in this set. Have tried the American 6BL7GT with success.

Geordie McBoyne.

[peter scott]

Would there be space in the bobbin to knit a few extra turns for the interlace?

Peter

[Geordie McBoyne]

Hi Peter,
I'd guess it would take at least two hundred turns over the existing windings. I'll take a look at the frame oscillator transformer later today.

Geordie McBoyne.

[Geordie McBoyne]

The Frame timebase circuit in the Pye BV20. The frame blocking oscillator transformer does not have a sync injection winding.
Capacitor C21A, the sync coupling has a value of 0.01uF.

Geordie McBoyne.

[peter scott]

Good solution.

Peter

[Geordie McBoyne]

Seems that the interlace filter design was not exclusive to Pye. The Pilot CV34 from 1950 employs a similar circuit.  The frame and line sync pulses are supplied to the cathodes of the Mazda T41 thyratron oscillators. It's an unusual arrangement but it works. Some time ago in an attempt to improve the interlace in a Dynatron "Fulmar" I modified the set to incorporate the Pilot frame sync and oscillator circuit.  In the Fulmar the the frame oscillator thyratron is a Mazda 6K25.

Geordie McBoyne.

[Geordie McBoyne]

Recently bought a Mazda UU8 for this set. Useless! Perhaps that's why it was so cheap. However, there might be provision on the mains transformer for a 5volt rectifier valve.
Some B16T power units were supplied with a Mullard GZ32 in lieu of the UU8. Also, consider the indirectly heated 5V4G?

Geordie McBoyne.