This set has no picture. Raster and sound are present. The brilliance control is operative although it does not blank the screen effectively. On band 1 a “slight” trace of sound -on- vision is
noticeable. I have interchanged valves 4 and 5
with valve 6 (sound i.f.) and tried substituting these 6F23’s with new EF80’s with no result. –
M. Day (Birmingham, 24).
You will have to check the V4 and V5 valve
base voltages, h.t. at pins 7 and 8 and bias at
pins 1 and 3. If these are in order, check the
CG12E (or OA80) vision detector diode (inside L18 -L19 can) also the video choke from this
diode to the valve base.