On 1 September 2015 at 00:54, tony duell <a...@p850ug1.demon.co.uk> wrote: > >> Hi, >> >> I traced the 18Khz signal all the way from the moment it enters the >> logic board until the video board (attached to the neck of the CRT). >> The signal is there (it has different shapes but it is 18KHz). The > > No, that is a different 18kHz signal. That is the video, which will > have a significant component at the horizontal frequency. It > starts from pins 6 (intensity) and 7 (video) of the DE9 connector >
Oh, I think I understand now Video is different than horizontal board. > You need to trace on from pin 8 to transistors on the main board, > right up to the flyback transformer. > I did. The 18KHz signal is present when it enters the board from the wire, it is also present on the collector of the following 2 transistors (the TR21 and TR22 which are part of the brightness limiter and horizontal driver respectively), also at the output of the T501 transformer and at the collector of the TR23 transistor (which is labeled as Horizontal out). I then traced at every pin until the flyback transformer input (pin 4). According to the schematic and the board it seems that is the signal path from the moment it enters the logic board until it reaches the flyback transformer. However the flyback transformer is definitely not outputting the voltages it is supposed to, as the manual tells me to measure 56.8V at the cathode of diode D504 which is basically connected to the output pin 6 of the flyback transformer and I only measure few mV. Could a winding of the FBT be burned somehow? Regards, Vlad. > -tony
