22-09-2017, 11:23 AM
From the Radios-TV Forum. Some discussion going on about the restoration of an HMV 900 by Brian Cuff and the possibility of reintroducing the 240/405 switch in very early production receivers. We're looking into those timebase chassis that might still have the cable forms to make this possible.
The switching of the timebase frequencies between 6,000/25 and 10,125/50 is easy because the components are located on the control panel, R27 and R28. See attached circuit. We have to determine the position of "Baird" capacitors C3 and C11 on the group boards and if the cableforms still exist to connect these capacitors to the standards switch. The line timebase switching is easy to implement, just a single pole two way switch is required. The frame timebase needs a two pole switch.
https://www.radios-tv.co.uk/forum/black-...irror-lid/
Geordie McBoyne.
The switching of the timebase frequencies between 6,000/25 and 10,125/50 is easy because the components are located on the control panel, R27 and R28. See attached circuit. We have to determine the position of "Baird" capacitors C3 and C11 on the group boards and if the cableforms still exist to connect these capacitors to the standards switch. The line timebase switching is easy to implement, just a single pole two way switch is required. The frame timebase needs a two pole switch.
https://www.radios-tv.co.uk/forum/black-...irror-lid/
Geordie McBoyne.
