So I have got this DE CPU board I'm repairing. I have fixed a few faults and got it booting and when in the machine everything working good.

The problem is "sometimes" when you boot "all 3 LED's come on and stay on". Then if you turn off and on again it tends to boot fine. It's just if that happens in the game all solenoids fire at once as you turn on! Scared the bejesus out of me...lol

Thoughts on what might cause intermittent boot?

Would it be the Blanking circuit? or Reset Circuit and if so where to start? I'm thinking Blanking but....

The machine is good. This is a spare board I'm fixing. Yes it has some acid damage. I neutralised it and cleaned it up as best as possible but im just about to replace the 555 anyway as I reckon it's the Blanking circuit

Replaced the 555 and sanded down the tracks in the Blanking circuit - cleaned with alcohol - and new resistors put back in.

All seems to be working well. Have booted on the bench about 50 times and in the machine about 10 and worked great every time... sorted