the issue is matching the correct yoke, you have a high impedance yoke on your tube so your chassis must match
the problem with many of the weiya chassis is that they are clones made in china and therefore the flyback may or may not be different and the circuit layout slightly different
i work on a lot of chassis and every single weiya/clone of this design that i have ever had come in for repair the flyback is bad
if you do an online search you will find a matching new chassis-yoke specs, tube size,power input type and neck pinout are all considerations when purchasing a replacement chassis