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Author Topic: [WIP] Midway space invaders  (Read 7763 times)
funkycochise
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« on: October 17, 2010, 11:50:10 AM »


Two weeks ago, during the roadtrip, I was gone to pick up a Space Invaders witch landed in 'aganim' house for some vacation.
It was then time for me to bring this back in the field.

1. Cabinet surgery

At the time of the roadtrip, I couldn't linger and dig deeper about the cabinet condition and running state.
So let's start with that today :

 Huh? don't believe the pictures, the cab isn't outside but inside a veranda.



Cabinet is really in good shape and conditions :



The cpo is what is in the most damaged (if I could use this word) :  
You can't clearly see on the picture, but the letters are well erased.




Pffff, not even 56000 credits :



Screen chassis, also in good conditions (despite 20 years old dry spiders liying around) :



Unlocking the cpo, locks are a bit rusted, but they're still working well :
Panel buttons are all there and seem to be working.



The Power Supply, including its huge capacitors :



The AC Transformer and the game pcb :
Interesting, there are
intéressant, il a des réglage de windings for 220, 230 et 240 V
In 1978, we were using 220V, maybe I could make some solder to fits current Voltage values.



On the pcb side, I did some research, in my current theoretic limits.
The day of the road trip, I got Two pcbs.
One named "space invaders" and this one, in the cab, named "space walk".

"Carotte", the previous owner, thought was a "Space Invaders" Bootleg.
But it isn't.
"Space walk" is also a midway game of the "Space Invaders" time, based on the same Intel 8080A harware, exactly like "space invaders".

As "Spacewalk" pcb was keeped in the cab, I was only with the "Space Invaders" pcbs to try to go a bit forward.

Intel 8080A based hardware has 8 proms locations on its mainboard.
But on my pcbs, there are only 4 proms. So I first tought there was some missing chips.
Using Mame for my search, I noticed that "Space Walk" was using those 8 proms (from A to H)
Quote
Z:\Mame\mame>mame spacwalk
sw.h NOT FOUND
sw.g NOT FOUND
sw.f NOT FOUND
sw.e NOT FOUND
sw.d NOT FOUND
sw.c NOT FOUND
sw.b NOT FOUND
sw.a NOT FOUND
ERROR: required files are missing, the game cannot be run.
Z:\Mame\mame>

Whereas "Space Invaders" was only using 4 :
Quote
Z:\Mame\mame>mame invaders
invaders.h NOT FOUND
invaders.g NOT FOUND
invaders.f NOT FOUND
invaders.e NOT FOUND
ERROR: required files are missing, the game cannot be run.
Z:\Mame\mame>

By pure chance, it's the one locatred on my pcbs. So it seems complete.

So, if as I presume, "Space Walk" became "Space invaders", I should find 4 proms on the "spacewalk" pcbs instead of the original 8.

And this afternoon, without surprise, I've found 4 proms on the main board, and written on the pcb label
the "Walk"  is  crossed with a red pen, with splendidi "Invaders" handwritten above it.  Cheesy


Okay, this pcb story is fun, but what is still actually working  ?



Three good news with this picture :
- The PSU is working
- The Screen chassis is working (nice bright picture)
- The video part of the pcb is working : nice standstill colored garbage pictture  Tongue

For the curious ones, Here is how it looks like in the mirror :



That's all for today. I'm gone with all the removable parts (except the pcbs), for full cleaning.

Sorry, I didn't take pictures of the stars sky nor the moon : it was a real pain to remove it, as I didn't know how the sky was tied.
But they're all in good shape, like the rest of the cab.  Wink

By the way, I said the cab was complete in the beginning. It's not completly true.
The back door is missing and also the keylocks.
I will have to build a new door.


See you.


edit :
update from yesterday :

Swimming pool for the masses...




« Last Edit: October 18, 2010, 07:59:55 PM by funkycochise » Logged
Q*ris
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« Reply #1 on: October 17, 2010, 02:02:15 PM »

Such an iconic cab, thank you for bringing it back to life and for the detailed pics !
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scr33n
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« Reply #2 on: October 17, 2010, 02:22:49 PM »

Such an iconic cab, thank you for bringing it back to life and for the detailed pics !

+1
Very interesting to follow, thanks !!!  Space Ace
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Laschek
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« Reply #3 on: October 18, 2010, 09:32:58 AM »

Congrats, Space Invaders is a very nice cab to have (and a boring game that I only play when I'm drunk  Grin).



Looks like there might be an issue with the reset circuit (on the power supply), you might want to check this: http://marvin3m.com/video/seawolf.htm

EDIT: here's a great document on Midway 8080 boards, it also explains the reset circuit, should be an easy fix if the failure is located there: http://www.cityofberwyn.com/bronzeage/VGL_VolVI_Seawolf.pdf
« Last Edit: October 18, 2010, 10:04:25 AM by Laschek » Logged
gyruss
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« Reply #4 on: October 18, 2010, 01:04:28 PM »

Congratulations on your catch, I would like to own one myself someday, not for the gameplay but for the historic value and the artwork/moon background, which is great imo..  Cheesy
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Vnera
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« Reply #5 on: October 18, 2010, 05:26:56 PM »

Congrats, Space Invaders is a very nice cab to have (and a boring game that I only play when I'm drunk  Grin).

Looks like there might be an issue with the reset circuit (on the power supply), you might want to check this: http://marvin3m.com/video/seawolf.htm

EDIT: here's a great document on Midway 8080 boards, it also explains the reset circuit, should be an easy fix if the failure is located there: http://www.cityofberwyn.com/bronzeage/VGL_VolVI_Seawolf.pdf

I like the game. its just that the difficulty ramps up really fast. Also great cabinets to work on. You dont have to leave the back of the machine to see the screen very nice when adjusting the sink brightness ect

I cant see the landscape on the pics your machine has it?
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funkycochise
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« Reply #6 on: October 18, 2010, 07:49:02 PM »

thanks for all you replies.
I will have a look at the reset circuit.

At present time I don't have so many time to spend on the cab, as
it sleeps in my mate's house, and also that he's actually in specialized re-education organism
for road wounded people : He had an heavy motorcycle accident several weeks ago.
I need him to go forward on the pcb fix.

About the missing translucent Moon and the stars landscape : yes they're all both present, in great shapes
once washed  Grin

even the cpo, that I washed yesterday looks very nice now, except erased letters.
But during this washing, I noticed that the buttons are a bit damaged (burnt, sun yellowed, ...)
I will probably need some new. (I've heard theay are difficult to find now)
I also see that the electric harness and the leaf mecanics behind the cpo are also very nice.

@gyruss : yes the mix of a classic video game displayed on a black & white screen,
coloured with the mean of that time, used with a miror allowing to add wonderfull stars landscape, black lighted from behind
with a moon floor in front.
All this "magic" makes this quite "simple" game really special, and adds lots of game-appeal.  Grin
 
And I think that's why I did the leap to buy it.


update from yesterday :

Swimming pool for the masses...



Yes, I need to take a picture of that damned stars landscape  Cool
« Last Edit: October 18, 2010, 08:00:58 PM by funkycochise » Logged
aganim
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« Reply #7 on: October 20, 2010, 09:35:15 PM »

It is good to read this wip (even if this n' is not from my house)
I hope to be able to help you of best than I can, now that I back at home for the week end.
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funkycochise
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« Reply #8 on: October 21, 2010, 08:39:29 PM »

It is good to read this wip (even if this is not from my house)
I hope to be able to help you the best I can, now that I back at home for the week end.

Sure ! It will at least avoid me from doing mistakes, as i'm used to !  Space Ace
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funkycochise
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« Reply #9 on: November 01, 2010, 09:03:43 PM »

Progress of the adventure for the day, with aganim and his precious tools :
overall the one on the right, my chinese "velleman" doing the trick for my own soldering needs...



for those who didn't guess what it is, it's a unsoldering device, including an air motorised pump.

Until now, I didn't succeed in getting hands on a pcb pinout matching the one have. Aganim did :

http://www.classicgaming.cc/classics/spaceinvaders/manuals/MidwaySI_SIdelux_Pinouts.pdf

This one match a last with the pin number in front of us :



For the beginning, let's verify the fluo tube connector
Nice, we have the expected 110V AC. Let's move on with the power supply.

After some pain search to find the components involved, we have verifyed the 3 output of the voltage regulators. We have the expected 5V, 12V and -5V.
Measure without load, pcb disconnected.



It seems that on this side it's ok. Let's see with a load linked. Pcb connected.

We measured 5V on the pcb connector. 5V is exacly the same. No voltage loss.
At this time, without any doubt about the continuity , power supply to motherboard, we did not check -5V nor 12V on the motherbopard connector.

In fact we are a bit obsessed with the  "Power On reset" circuit part. After some check on tyhe pcb, we see that circuit is made of 2 transistors, 4125 and 4123, with a resistor and a capacitor. Explanation :



Let's check the resistor, with our unsoldering skills, this sould not be a problem :
I have chance, my multimeter includes a transistor tester, that I never used before, Time to make a try :



With datasheet of each transistor, one PNP, the other NPN, we check the range of work for each one. It's okay, they're both workking.
I can solder them again.

Arrived there, we don't want to bring the oscilloscope, to check if the "Power on reset" is generating it's pulse.
As we have gone a bit fast with the voltage check on the motherboard pcb, we decide to go this way first.

Note : It's a real pain to make measurement on the cabinet itself, You have to spend many time for a simple safe measure.

We check the wires on the connector that we have to measure.



No choice, we have to go with spike probe. Results : 5V is there, but alone. No 12V nor -5V

Let's verify continuity from motherboard connector to female PSU connector :
All right.
 
On PSU side, we verify from each regulator output to the male connector : all right too !

Damned, we check again from the motherboard connector to the PSu connector, male and female assembled. Power on. Still no voltage on the
motherboard.

WTF ? Where's the problem ?
On the female connector :



You don't see many thing on this picture, but 12V and -5V contacts are a bit larger than their neighbours. They should not make contact anymore.
I'm a bit surprised about that.
Even after contect cleaning spray over the connector, Impossible to get any continuity from the regulators outputs to the motherboard connector.

It's now dark outside, We won't go much more forward today. We're a bit perplexed about those anoying miscontacts.
Also we didn't see anything that could allow us to remove the pin inside the connector.

nevemind, it will be for next time...
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Etienne MacGyver
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« Reply #10 on: November 01, 2010, 10:09:57 PM »

you can try to use a mini screwdriver and "squeeze" the connectors a bit close so they will make contact

is you still dont have any power with the board connected, there must be something wrong with the board i think..
also a little sandpaper winded around a small pin and sand the insides of the connector can help, maybe its corroded..
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aganim
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« Reply #11 on: November 01, 2010, 10:10:13 PM »

Cool a fast report  Grin

Molex  Evil , strange problem but we have to admit that the tensions do not pass this point of cut....

I hope I can remake the contact to be able to make a good contact. Find an identical connector seems to me very difficult.

The continuation in next episode....

 Evil to be to intern.....
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