Need advice on a Sony Watchman FD-10

[Richard D]

Hello all, Can someone tell me how to increase the brightness on this Sony FD-10. The contrast is good and I looked inside for a trim pot and can not find one. Actually I found about five trim pots. But none for brightness or brightness range. I found vert. lin and focus but no brightness. Maybe someone knows where I could look at a schematic. Thanks.
Richard.