Pinx's Space Invaders Pinball cont...

Bally Space Invaders Pinball

Restoration cont...

Memory capacitor.
I bought a 1 Farad memory capacitor from Maplins, to replace the battery i removed, these as i mention'd before dont suffer from any leakage when they become old. As the pins on the capacitor are very close together, it will not fit into the origional holes for the battery, so i had to drill a hole just to right of the positive solder hole (see pic above right)
Once i had the hole, i heated the solder in the positive hole and pushed the capacitor in, i then solder'd the back of the positive pin. The negative pin (nearest black band on cap) was then obviously in the hole i had drilled, which has no solder contact point, so i bent the leg outwards and solder'd a length of black wire to it. (see pic right)

Memory capacitor cont..
I then heated the solder in the negative hole and pushed the other end of the wire into it, i finished off by turning the pcb over and adding a blob of solder to the end of this wire. It was now securely attatched and ready to work.
This modification can be done the other way round, by drilling a hole near the negative solder hole and running a length of red wire from the positive pin to the positive solder hole, but i prefer to keep positive jumpers to a minimum on the back of a pcb, as it keeps the risks of shorts to a minimum, hence me doing a negative jumper instead.

Solenoid Driver pcb.
This pcb, tells all the solenoids (coils) on the playfield when to fire on and off and as with some of the other pcb's in the machine, this needs some modifications and upgrades. This pcb is also the one that holds the High Voltage section, making it dangerous to work on.
WARNING, if you do not know what you are doing around high voltage pcb circuitry, do not attempt this, as there is a high risk of electrical shock from either of the two large blue capacitors !

Solenoid Driver pcb cont....
The large blue capacitor in the middle of the pcb is known as C23 it is a logic filter capacitor and due to the age of this component, it is probably no longer doing its job properly. It's job is to smooth out the 5+ volts, going to all the logic pcb's in the game. It is a 20 volt 11,000 mfd capacitor, but it is better to replace it with a larger one.

Replacing C23 capacitor.
I managed to get a 25 volt 15,000 mfd capacitor, from RS, which was only a little smaller in physical size. I then unsolder'd both leads from the bottom of the old C23, making extra special care not to short between these two pins by accident (nice large pop if you do !)
Once the wires were free from the pins, i then used side cutters to cut off the two cable ties holding the capacitor to the pcb itself.
It was then a case of fitting two new cable ties through the holes and doing them up around the new C23 capacitor (this one was black in colour, see pic) This capacitor is polarised and therefor has to have its positive and negative sides connected up correctly!
On the pcb by one of the wires to the capacitor there is marked a + for the positive connection, i twisted the capacitor around in the cable ties until the postive pin was in line with the positive wire. (the capacitor is marked for negative side only)
It was then a simple case of soldering the correct wires to relative pins.

Solenoid driver pcb, jumper wire mods.
These pcb's also suffer from circuitry not up to the job required, so some jumper mods need to be done here too. First i added a black jumper wire from the solder point of the negative lead on capacitor C23 to the thick ground trace directly below it. This relieves pin 10 on connector J3 and stops it from burning (jumper in middle on pic). I then added another black jumper wire from the solder point of the negative lead on capacitor C26 and solder'd this to the ground trace at the edge of the pcb (jumper top right in pic) this helps to stop pin 3 of J3 from burning.
Lastly i added a 5V+ jumper wire from the solder point of TP1 (test point) to the solder point of TP3 (test point) in this pic it is black (jumper on left), as i had run out of red wire, but it has now been changed to red wire. I like to keep ground jumpers black and voltage jumpers red, so at a glance i know what i'm dealing with. Adding this jumper helps to prevent unreliable game play.

It's Alive, YAY !!!
I replaced the solenoid driver pcb back in the backbox and as i had already fixed and modded the MPU pcb it was time to take the plunge and try turning it on again.
This time i got all lights a couple of clunks as the targets re-set and then the rumbling sound it does as it boots up and goes into attract ! YES it was alive and quite happy sitting in attract mode. There were still 35 credits showing the the credit window and the chaser lights on the infinity backglass, were going around and around enticing me to play it, so i did : )
On my 3rd game i called to the wife (pinxy) to have a go and this is when things started to turn pear shaped !
I could see whisps of smoke coming from the playfield, so i turned the game off, lifted the playfiled and found one of the thumper bumper coils was locked on and smoking, so i unsolder'd the positive wire from this coil and turned her on again...

But an hour later.....
...This time even more smoke and the sound of crackling, looking in the coin door i could see smoke pouring out of the transformer along with a load of goo that looked like melted Red Leicester cheese : ( Not good, not good at all !
Taking the power supply out again and removing the transformer i could see just how bad it was (see pics) it had gone into complete meltdown and in the process blew the fuse in the mains plug too !
Trying to source one of these transformers was going to be a nightmare so i rang round a few places and got quoted £70.00 to £150.00 to make a new one, this was a bit off putting, but it wasnt going to work with out it, so i made an appointment to go and see a company about making me one. Just a few hours later though, i rang them back and cancelled as.......

Used replacement transformer.
.....a mate from #Jamma (Dsyde thanx again joolz) got in touch and told me that Arcade Warehouse just happened to have a Bally Space Invaders breaking for spares, so i paid £20.00 for it and got it shipped down. When it got here though i wasnt too impressed with it, as it looked as rough as anything, the rectifier pcb had been hard wired on the connections and wire had been solder'd across the fuses !!

The transformer was rusty and looked very sorry for itself, i was not optomistic of it working at all, but as i had paid 20 quid for it plus the shipping, i had to give it a go. I unsolder'd all the wires off the transformer, which took some time as the solder was very old and didnt want to melt, so as a cheat i squirted liquid flux on the solder and then added new solder which helped the old stuff melt. I then bolted the transformer to the good power supply and solder'd all the wires on.

Locked on coil.
Before i got tempted to turn it back on, i decided i would sort out the locked on coil on the thumper bumper which had also burnt. For a coil to be locked on, either the transistor or the diode on the solenoid driver pcb for that coil is faulty. So i removed the solenoid driver pcb again and meter'd all the transistors, and found one with a very low reading, so i replaced this with a new TIP102 transistor, i also meter'd all the diodes but these were ok.
I then order'd 2 second hand coils one for the job in hand and one as a spare. I had to undo 5 nuts and 2 screws to get the coil and bracket out as it was locked in solid and wouldnt budge, i also unsolder'd the remaining wires to it. It was then just a matter of fitting the replacement coil to the bracket, bolting it back in to the playfield and soldering the wires back on.

In pic, burnt coil on left, replacement on right and the duff transistor in front.

Flipper leaf switches.
Whilst giving the pinball a once over, i noticed that the flipper leaf switches were badly pitted so they were almost non existent on the contacts, so when i was over Swallow Amusements getting a few bits for my video games, i got a couple and fitted these.
It was just a matter of unsoldering the wires from the old ones and undoing 2 screws that hold them to the inside of the table. As the new ones were thinner in the wooded section, i took them apart and add bits from the old ones, untill they were the same thickness.
Then i just screwed them back into the table and solder'd the wires back on.
(in pic new one in front, spot the difference)

Another little job done.

New Rubbers.
All the rubbers on the playfield were really showing their age, they were all yellowing in colour but some were perished. So i bought a whole new set from Pinball Heaven along with a couple of new Balls. Replacing these only took about an hour, it just meant carefully removing some of the playfield plastics, taking the old rubbers off and putting the new ones on. The new rubbers have marked on the side of them what size they are, so i just corresponded each rubber with the chart in the manual as to what size goes where on the playfield.

pic on right shows how the slingshot rubbers have stretched and aged in comparison to the new ones.

Alive again.
So, it was time again to turn it on and luckily everything was fine. I left the coin door open for the first couple of hours, so that i could check there was no smoke coming from anything (probably down to paranoia), but it behaved itself and played perfectly.
All that leaves me to do now is, replace about 5 dead bulbs in the playfield and sort out a slight hum on the audio, which is either down to a bad ground on the sound pcb or some dried out capacitors on it.
Whilst i was in the backbox refitting the solenoid driver pcb, i meter'd the 195 vdc line and adjusted it down to 170 vdc, as this helps prolong the life of the score displays. They still work perfectly at the lower voltage, so its a worthwhile thing to do.

! WARNING, the adjustment for this voltage is under a safety cover, as this area of the pcb is Dangerous to work on !

I am happy to say that it has been working fine for a week now and is getting alot of use (i cant get pinxy off it), as with the Pole Position project, this was a quick but rather intense project and with it being my first in pinball repair, i am very pleased with the outcome.

UPDATE...
This is the sound pcb, and as i mention'd earlier, i had a very slight hum sometimes, depending on how much load was on the game. I figured this to be a bad ground as the pcb does'nt ground itself against its mounting points, it only gets its ground from pins 6 and 14 on connector J1.
TP3 (test point) is a ground point, so i added a length of black wire to the solder blob on the back of TP3 (see pic bottom left), i then mounted the pcb back in the backbox and measured the black wire off to the nearest mounting bolt hole. I then cut the wire to this length and crimped on an eyelet, it was then just a matter of putting the bolt through the eyelet crimp and bolting it to the pcb mounting point. (see pic bottom right)

As with all my projects i like to thank any people who helped,
so a BIG THANX goes to the following people :

For help : Alan, Willie, Malc, Joolz,
For parts: Steve at Swallows, Pinball Heaven, Arcade Warehouse
and finally John Whyatt, who was an endless supply of technical advice and parts.

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