UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Baird T18

TNC · 14th Feb 2007, 11:48 am

Hi John/Steve

Attached are details of the Baird T18 circuit. The focus coil is shown on the top r/h corner of the time-base diagram...it connects via the socket the HT feed (but not going through the smoothing choke L37 as the other HT feeds do). I assume the adjustment VR3 is a variable power bleed to earth.

The contrast control (to help, also denoted as VR3!!) is located to the l/h side of the vision socket shown on the r/h side of the larger diagram and via that socket connects to points 4 and 5 which are to be found to the lower centre-left on the vision diagram. 6 on that socket is HT.
It looks to me as if VR3 is some sort of feedback control - but I may well be wrong on that!!

HTH, Trevor.

14th Feb 2007, 11:48 am	#5
TNC Hexode Join Date: Apr 2003 Location: Westcliff-on-Sea, Essex, UK. Posts: 386	Re: Baird T18 - focus problem. Hi John/Steve Attached are details of the Baird T18 circuit. The focus coil is shown on the top r/h corner of the time-base diagram...it connects via the socket the HT feed (but not going through the smoothing choke L37 as the other HT feeds do). I assume the adjustment VR3 is a variable power bleed to earth. The contrast control (to help, also denoted as VR3!!) is located to the l/h side of the vision socket shown on the r/h side of the larger diagram and via that socket connects to points 4 and 5 which are to be found to the lower centre-left on the vision diagram. 6 on that socket is HT. It looks to me as if VR3 is some sort of feedback control - but I may well be wrong on that!! HTH, Trevor. Attached Thumbnails