Aug 192012
 

I’ve just recieved a Space Invaders Part II, which was thought to have a PCB fault.

On powering up the cab I observed the following conditions:

1) Very faint looping UFO sound
2) Monitor Neck Glow
3) Nothing on screen

The first thing I did was check the voltages on the “G connector” on the PCB.

I set my multimeter to 20v DC and measured ground (Pins 1,2 or 3) and Pin 5 (or the blue harness wire). I expected to get around 12v. I got 12.1V

12v

12v – Space Invaders Part II

I measured ground (Pins 1,2 or 3) and Pin 7 (or the grey harness wire). I expected to get around 18v. I got nothing!

18v

18v – Space Invaders Part II

I measured ground (Pins 1,2 or 3) and Pin 9 (or the red harness wire). I expected to get around 5v. I got nothing!

5v

5v – Space Invaders Part II

I measured ground (Pins 1,2 or 3) and Pin 10 (or the white harness wire). I expected to get around 0v. This is the Power-on-Reset signal, and should be close to 0v for the game to boot. I got nothing!

0v

0v – Space Invaders Part II

So, my conculsion was that I had some kind of power issue, and my attention turned to the Power brick. With the cab switched off, I put my mutimeter on continuity and checked each power brick fuse.

Powerbrick

Powerbrick – Space Invaders Part II

Fuse 1 – Continutiy
Fuse 2 – Continuity
Fuse 3 – Continuity
Fuse 4 – Nothing!

Luckily I had a spare slow blow 5A fuse that I could replace the fault one with.

I powered up the cab and voila, we have a working game!

Working SI

Working Space Invaders Part II