Hi fellow Pinsiders,

I am working on a Williams System 7 Pharaoh, and I am having a strange problem. The game boots fine three out of four times. The fourth time, however, it does not boot. Instead it waits a couple of seconds and then the coin lockout solenoid activates repeatedly and some playfield lamps start to flash brightly as well in a steady rhythm. The displays also shows zeros in the same rhythm and it all feels very dramatic so I switch off very quickly. Turning it on again, it works fine for the next couple of boots. Any thoughts at what I am looking at here?

Further info on the game is that the dreaded 40 pin connector has been rebuilt, I have installed NVRAM and once the game boots it plays fine except for one of the sounds sounding like static.

Any thoughts are welcome.

Cheers,
Archieball

Here is me fumbling in the dark: can it be that the caps in the power supply, especially the big C10, are going bad and that this hinders the power to stabilize before the blanking circuit kicks in? Either that or that the cap in the blanking circuit itself (C31) or the PIA (IC18) is bad? The reason I suspect a cap problem is that the problem seems intermittent. Then again, I am not sure that the rythmical pulsing of the lights and the coin lockout coil has to do with the blanking circuit at all.

I am in deep waters here. Any input most welcome!

Thanks for the replies, guys. barakandl I am not not entirely sure about how I should approach what you suggest, but I tried the following:

Put my meter clips on either side of the C10 18000 mFd 20VDC capacitor. Put my multimeter on the lowest AC setting I have which is 200VAC. Switched the game on. It read a slowly decreasing value starting from around 16VAC and creeping downwards. First quickly, then slower and stabilizing around 2.4 after a minute or so. Is this what is called a ripple?

I tried the VDC testpoints on the power board first. The +12V seemed a bit jittery, fluctuating between 12.0 and 12.9. The -12V point measures -14. On the MPU the +12V unregulated testpoint seemed even more unstable, but it never went lower than 12.0 and never higher than 13. The +5V testpoint shows a dead steady 5.03VDC on the MPU.

Brypten I haven't changed any sockets, but I've verified that I don't have the scanbe ones. I do however have the white ones on my soundboard, and I guess I'll have to change these.

Thanks MarAlb !

I have now ordered the 18000 mfd cap plus the caps for the rest of the power board. I'll try replacing the big mutha first and if that doesn't help I'll do the rest. Fingers crossed that will solve it.

Update on this: I'm afraid changing the 18000mfd cap on the PSU didn't change anything. The game still fails to boot every third or fourth time.