Hi again Saevar
I should add that if the HV multiplier has failed the oscillator will not be able to start and will draw a high current due to the load on it, it will then blow the safety fuse, just what you are seeing.
G Edmonds
On Wednesday 10 July 2024 at 21:38:06 BST, saevar <saevartj@...> wrote:
Hi all,
Thanks for your valuable advice.
George, what makes you conclude that the A1A11 is faulty?
I am not that familiar with CRT circuitry and am therefore a bit lost as to how to test these various parts (without risking my health), i.e. ringing test and how to excite the main winding with an RF oscillator as Dave mentions. Any further advice is much appreciated.
To make it more clear what is faulty is, the overview figure below shows the display circuits. On the far left is the A1A6 and in the center is A1A3 high voltage regulator.
The HV oscillator does not oscillate and the fuse at the 23V supply is blown every time.?
The HV oscillator is shown in more detail in the images below with the Q7 transistor, who's collector and the 23V supply are connected to one of the primary transformer coils.
The Base and the output of the OSC drive are connected to another transformer coil for feedback.
