UE15 and UE15 to be OK, connected as expected and inverting but the 555 is always high on pin 3.
The 555 has got 5V on pins 4 & 8.
C50, 51, 52 look OK / visually, although perhaps C52 looks a little dark.
I guess something here has to be faulty.
What's more likely ...the 555 or one of the capacitors? I have 555's (TLC555IP) to hand if needed - they are functionally compatible right? I also got some 50V 0.1uF ceramics today.
I have not got the circuit in front of me, though as I recall, at power on, the trigger pin is transiently low, because of the discharged 0.1uF capacitor on in 2.
The timing capacitor and resistor, typically 1uF and 1Meg are connected to pin 6&7 and determine how long pin 3 stays high after power up.
Since the 1uF is a Tant capacitor, if it was shorted, or leaky, the 555's output on pin 3 would trigger to a high state, but then not fall low later because the threshold voltage would not be reached.
So that 1uF capacitor is more of a suspect than the 555 IC itself, because old Tants notoriouly short out. But this is just probablility, your 555 IC or other parts around the 555, could still be defective.
Generally a 555 IC itself, especially the vintage Signetics NE555N are pretty reliable.
Of course you could check with a scope if the 1uF cap had charged to over the threshold voltage, typically 2/3 the supply voltage, but if you did you have to use a x10 probe with a 10 Meg input resistance. People get fooled checking this with a x1 probe with a 1 Meg input resistance, because that simply loads the voltage to half Vcc because of the 1 Meg charging resistor.
