I have included a scan on the video detector and output on the 991 Schedule C/D.
It does seem to be a very basic circuit lacking in lots of components, detection and cathode load are both done with diodes. OK a metal one in the cathode.
L23 and L24 are wound coils on formers. R33 & R34 were replaced when I worked on the set as was C28 in the noise limiter all though this is wound off.
The Resistors and caps from the brilliance control to the R1123, R114 & R118 and the two caps C88, C89 were also replaced.
I have just looked at the 3K9 resistor R28 that was high so I decided to change it, in doing so I also found that the coil L21 was open circuit with a wire off at one end of the resistor, this was sorted and it all put back together. No noticeable change to the picture that I can perceive.
Adrian
If there is anything one should consider I look at please let me know.
It does seem to be a very basic circuit lacking in lots of components, detection and cathode load are both done with diodes. OK a metal one in the cathode.
L23 and L24 are wound coils on formers. R33 & R34 were replaced when I worked on the set as was C28 in the noise limiter all though this is wound off.
The Resistors and caps from the brilliance control to the R1123, R114 & R118 and the two caps C88, C89 were also replaced.
I have just looked at the 3K9 resistor R28 that was high so I decided to change it, in doing so I also found that the coil L21 was open circuit with a wire off at one end of the resistor, this was sorted and it all put back together. No noticeable change to the picture that I can perceive.
Adrian
If there is anything one should consider I look at please let me know.
Learning as I go!
Youtube EF91 Valve
Youtube EF91 Valve
