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need help identifying and repairing


Lai

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Hey everyone . so i bought this “space invaders” cocktail machine made by lai. so far i havent been able to find any info on it . currently it doesnt work . it kinda made noises when i got it . but i saw some leaky electrolytic caps on the game board . so i repaired the corroded traces and put new caps in it . but now it makes one constant noise. The monitor makes the typical noise but no picture. It also had corroded traces and a leaky cap which i replaced . I have no idea if the monitor is faulty or the game board or both. So currently just looking for any info on what gameboard is in it . it definitely made space invaders noises though20161203_201652.jpg20161203_201811.jpg20161203_201804.jpg20161203_125223.jpg20161203_201852.jpg20161203_150339.jpg20161203_201831.jpg
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The PCB is one of the dozens of Space Invaders clone boards manufactured back in the day. The good news is that most have similar hardware to the originals, so repairing them is normally simple. I'm guessing it's a Z80 based PCB with 2716 Eproms (I could be wrong). Check your voltages to the PCB first off and re-seat all socketed IC's.

 

Regards,

 

Johns-Arcade.

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The PCB is one of the dozens of Space Invaders clone boards manufactured back in the day. The good news is that most have similar hardware to the originals, so repairing them is normally simple. I'm guessing it's a Z80 based PCB with 2716 Eproms (I could be wrong). Check your voltages to the PCB first off and re-seat all socketed IC's.

 

Regards,

 

Johns-Arcade.

 

Yeah i figured it would be . its definitely running on a z80 processor. I checked the power supply with the board plugged in and it show nearly spot on -5v 5v and 12v rails. I`ll try reseating the roms report back . thanks john

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Also the monitor only has one input . i heard early machines were composite video out like a normal tv . so would that mean i could plug anything that outputs a composite signal into it to test if it works?
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Like say, the early machines used composite video, they actually uses real tv hardware to keep things affordable. So plugging in a composite signal should give you an image on the screen. You might however use a device you don't really like because if there is something wrong with the monitor it can break the device.
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I got the same type of machine/game pcb here. The main cpu on mine is a 8080 not a Z80.

 

You can connect up a composite signal to the game pcb no problem but that noise your hearing from PCB is basically the games not running program roms correctly.

 

This is the same issue mine did and was found to be bad rom sockets causing the issue all the time. Going by the screen burn its a Darth Vader as i can see the game logo burn in the middle which is what my game is

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Like say, the early machines used composite video, they actually uses real tv hardware to keep things affordable. So plugging in a composite signal should give you an image on the screen. You might however use a device you don't really like because if there is something wrong with the monitor it can break the device.

 

I tried an old vcr i know works and still no image . checked a few things. Might try recapping it and seeing if it fixes it. When i turn it on the neck on the crt glows and it makes the normal crt noise just no picture

 

- - - Updated - - -

 

I got the same type of machine/game pcb here. The main cpu on mine is a 8080 not a Z80.

 

You can connect up a composite signal to the game pcb no problem but that noise your hearing from PCB is basically the games not running program roms correctly.

 

This is the same issue mine did and was found to be bad rom sockets causing the issue all the time. Going by the screen burn its a Darth Vader as i can see the game logo burn in the middle which is what my game is

 

Yea after another look it is a 8080 as well. Can`t seem to make it work . somethings definately wrong. I tried reinserting all the socketed chips . still no luck. I`ll probably have to fix the monitor first and go from there . Funny how its branded as a space invaders machine . even has the japanese instructions under the english ones but its a darth vader. My monitor is a matsushita.is yours the same?

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A quick trick to check and see what may be the problem with your monitor board is to turn up the screen voltage.

On the flyback transformer that has the wire that goes up to the crt you usually have 2 pots. 1 is focus and the other is screen.

Mark where it is so you don't forget and turn it up while looking at the screen.

You can fault find a whole heap of problems that way. If you get the whole screen come up white, you have eliminated most everything up to the video input.

You may find, and this is very common, that you have no vertical deflection, which will show up as a white line across the middle of the screen (long ways). it could be no Hor deflection, less common, a line down the screen (short/width ways) no deflection at all, a dot in the middle.

Just remember, if you do turn it up, don't go too far, only far enough to see something. It won't make a massive difference on your crt as it is already burned, but if you do have a deflection problem, you can burn the screen if you leave it up too high for too long.

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Yea i cant remember if it has the adjustment pots on the transformer. Did a bit of research . it seems to be a repurposed panasonic bw tv from the early 70s . the thing is when i turn it on i get the typical crt noise but no display whatsoever. Quick probe around shows the flyback is getting voltages. Maybe the hv output diode is bad or the flyback driver isnt working?
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Ok so it's been a very very very long time since my last post . I ended up re-caping the gameboard and fixing some traces (from the electrolyte corrosion) it works when plugged into a normal tvs composite output. It ran as normal except it only had one sound . After a bit of research i found that it was also common on genuine space invaders boards that the ram goes bad. So I ordered some new chips and sockets and that fixed all the audio ! Now this was in 2017 . I also played around quite alot with the monitor but could never get it to work . After recapping it and fixing some broken solder joints it made all the correct hissing and whining noises you'd expect to some from the high voltage and the yoke . But it still had no picture . So I did play around with the possibility of using an ordinary tv but 12 inch wasn't common especially in black and white . After deciding it was too much mucking around and modifying I put the machine in the corner of the garage and left it there collecting crap on top it .

 

Back in 2017 I also repolished the leg bottoms and repainted the legs silver while i was at tafe.

 

So 2019 comes around and I spotted a national panasonic tv for sale which was the exact one i needed. 50 bucks later and it was mine. Took it home and pulled it apart and thought heck why not, lets try and put the arcade monitors tube inside the tv . (They are the exact same also) with the arcade machines tube in the tv it was completely dead . No picture at all so it must've had a dead gun . So then i took the tvs tube and tried it with the arcades chassis and it works! And what a great picture! Nice and bright and zero burn in unlike the previous . So now its time to put it back together properly and finish it.

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5b92b24c4ecf0964e6dc74accdc72027.jpg

 

The poor tv that gave its life for a better cause

 

c7531622b0e491c2b7b582f2e4098ba9.jpg

 

And thats what it looks line in the machine half put back together

 

Sent from my SM-N960F using Tapatalk

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