After it’s on for for a bit, the level meter, display lights and the am/fm display all go dark
It's a power distribution wiring problem (cracked slobber joint?) or the FU4 3 amp fuse has gotten tired.
INDEPENDENT lighting areas to stringently VIEW and report:
am / fm / phono / aux 13v DC through 150 ohm dropping resistor to one of four 8v 50mA lamps
speaker a / speaker B 7.5vac to 8v 50mA lamps (no dropping resistor)
main panel lights 7.5vac to three 8v 300mA wedge lamps. (no dropping resistor)
VU display 7.5vac through 2 x 18ohm dropping resistors for heater
Tuner display. 7.5vac through 2 x 12ohm dropping resistors for heater
Power Supply, 7.5vac from the transformer. FU4 3 amps on the power amp board and the pads NEXT to it that have a jumper wire are the inlet and distribution point for the main panel lights, the two fluorescent display modules (their heaters with appropriate dropping resistors: 2x18 ohms for VU and 2x12 ohms for tuner) and the speaker indicators (the am, fm, aux and phono run on 13v dc through a 150 ohm dropping resistor).
It comes from the blue transformer wires connected to pins 7 & 8.
It goes through the fuse and the jumper where the pads for another fuse are.
so:
Check fuse for fatigue and sagging,
Check solder joints or just (if you are good at soldering) resolder them.
The time delay to lights out / back on is a heating / cooling cycle that has invaded some solid wiring. The additional resistance of the defect causes heating expansion and eventual disconnection, then it cools and reconnects itself as it contracts.
I may, if we have trouble, go back and edit THIS post to explicitly call out each pin that carries current to each of the named displays to locate the EXACT section of foil on the pc board.
I HOPE it doesn't come to that.