I am repairing a power board in a Casio FZ-20M sampler - and while I've got the 5V, 12V, and 15V rails up and working the EL backlight doesn't seem to be doing what I'd expect.
The schematic is attached - the circuit is powered by the 5V rail, and I'd expect it to be putting out 90V AC - but it actually measures 140Hz 9V AC without a load. I've tested the caps, resistors, and transistors and all seems in range.
I wonder if I'm missing something, as I'm not too familiar with how the circuit works - could anyone help me diagnose? In particular, I'm wondering if this needs a load in order to work correctly. Thanks!