You are on the right track. I would also change out any old electrolytics.
I find swapping old ones for new ones clears up an awful lot of flaky problems with 20-30 year old electronic gear.
It has brought my Fujimoto CP31 roller processor and wash dry unit back from the dead, as well as a few different Vivitar timers.
The other thing Vivitars have is a zerner diode and resistor voltage reference. The resistor burns up, and all stops. I replace this resistor and zener with a regulator, and all is happy again.