Midway upright
Space Invaders
PCB + Power Supply
voltage measurements

last updated June 24, 2016



 

Andys-arcade

 

IF YOU HAVE A TAITO COCKTAIL, CLICK HERE!

 

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INTRO :
In order to confirm the correct operation of your space invaders machine, or to determine which major part is at fault, it is neccesary to measure the voltages coming from your power supply. The easiest and safest way to do this, is the main aim of this page.

Midway machines this applies to :
- Space Invaders Upright
- Space Invaders Cocktail
- Deluxe Space Invaders Upright

- Deluxe Space Invaders Cocktail

WHAT YOU WILL NEED:
- a Digital Multimeter, doesn't have to be too fancy, anything that measures DC voltages
- about 10 minutes of your time

Firstly, open your machine up and locate the 'L-shaped' PCB.. . If your machine has power supply problems, it is advisable that you do not leave your machine switched on for too long during this process, try to complete all measurmenet in less than 3-5 minutes to avoid damage to the game pcb.

There are two connectors of interest, the main PCB connector and the daughterboard audio/power connector. The photos below will show you the obvious differences.

We are starting our measurements at the main board connector, you do not need to unplug anything at this time, you simply probe the silver pads on the pcb with the power switched on. Do not touch anything else in the machine, there are live and exposed voltages here, you risk electrocution if you do.

SET YOUR METER TO DC VOLTS - if yours is not autoranging, then set it to the 20v range.

The pin numbering starts with 1 on the left, count across to find your pin number. Place your BLACK probe on either pins 14, 15, 16, 17 (any of them is fine) and then follow the instruction table below, moving your RED probe:

 

 

photo
Pin
harness wire colour
voltage
acceptable
range
used for
1
WHT
5v
4.9 -> 5.1

TTL game Logic

3
WHT/BRN
12v
11.5v->12.5v
RAM power
5
BLK/WHT
-5v
-4.9v -> -5.15v
RAM power

 

 

Now you have done the main connector measurements, you need to move to the daughterboard.

CAUTION - be careful not to force your probe leads into the connector, or to slip with tyour probe leads and short the pins!

The pin numbering starts with 1 on the RIGHT, count up towards the LEFT to find your pin number. Place your probes as show nin the photos:

 

photo
Pin
voltage
acceptable
range
used for
BLACK - 10
RED - 11
~17v
12v -> 19v

Audio Amplifier voltage (non critical for accuracy)

BLACK 1 or 2
RED - 6
< 0.5v
0v -> 0.5v

POR
(Power On Reset)

 

Notes on the POR  
This is an ACTIVE signal that should be at <0.5v when powered up. When you cut the power, this will jump up to about 4.5v and slowly decay back. Your meter may not sample quick enough to see this happen in real time, but its not important. Likewise when you power up, the signal should immediately go to 4.5v and drop down again in under 10ms, again this is all too fast for any multimeter to 'see'. All you should verify is that it sits at less than half a volt when everything is powered up.

 

 

Summary

And thats just about it! If you have measured everything described on this page correctly and your game still doesn't boot up, then your game pcb is probably bad. If you are not measuring what you see above then your PSU will be bad, but also your game pcb could also be bad as well.

I do repair these pcbs on a regular basis, so please enquire if you need assistance. I do also sell working pcbs and parts and will take your faulty pcb as a trade-in against a fully working board.

Andys-arcade

 

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These pages are (C) Andy Welburn 1996-2002. I cannot be held responsible if the information supplied herein results in a blown monitor/power supply/house fuse/mind. Oh yeah, have a nice day :)