I need some diagnostic assistance from the electronics gurus.

I'm working on repairing my mother's retro sewing machine from the 90's a Pfaff 7550 to be exact. The problem it has at this stage is a prolonged startup, like it has a power supply issue. She tells me it was starting more quickly on a warm day.

I've opened it up and given it some power, it sits with a largely blank screen, the stepper motor for the foot control ticking back and forth until at some stage it fires up to life.

My gut feeling is dry capacitors or something to do with the power supply transformer.

Any ideas or maybe tips on testing capacitors etc?