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Faulty Taito Space Invaders

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Haves1979 View Drop Down
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    Posted: 05 May 2019 at 12:31pm
Hi all, my recently purchased working taito space invaders has lasted a few weeks and has gone faulty already. This is the one with that three board set I believe.

I'm new to arcades so not really sure where to start. I was intending to get the braze multigame set anyway, this comes with an fault check so not sure if this is still worthwhile.

- The machine powers up and monitor and fan work
- the screen just displays thin lines across it with a line of garbage text across the top.
- No controls work and there is no sound.

The guy I bought it from did recently have the board serviced and rams replaced. Having read a few posts I think it may be these again, are there any quick checks I can do?

Any pointers on where to start would be great.

Cheers
Chris

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Post Options Post Options   Thanks (0) Thanks(0)   Quote yorkshire_spam Quote  Post ReplyReply Direct Link To This Post Posted: 05 May 2019 at 1:23pm
I don't know anything specific to this board, but questions I would ask....

Have you checked the voltages at the PCB? Some of the ICs might rely on "odd" voltages being accurate.

What parts are socketed on the board? CPU? ROM? Ram? any of the logic?
Which of these do you have spares (tested? known good?) for?

What kit do you have? 
Soldering iron? Multimeter? Logic probe? 
Cheers, Sam
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 05 May 2019 at 2:28pm
Looks like the cpu is trying to run but failing.
The fact you have characters at the top of the screen means something is happening and the reset is ok.
Like yorksire_spam says it could be down to voltage.My space invaders board will do random things if the voltage isn't just right.
First check to make sure you are getting +5 +12 and -5V because if the -5V is missing it's going to damage chips.
Then look on the psu and see if there is a 5V adjust.
if the voltages are good and adjusting does nothing it could be a rom gone bad.
You rang......?
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Haves1979 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 05 May 2019 at 5:44pm
Spot on thanks both, I'll dig out the multimeter and see what I have.

No spares unfortunately, but I do have a soldering iron. Cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2019 at 8:18pm
Thanks for above and I have managed to get hold of a multimeter. Where is best to take the voltages from? There are two points for 12v and 5v on the board, are these ok? These are reading around 13 and 5.3.

Sorry not really sure what I am looking for so all advice appreciated.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stevros Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2019 at 8:22pm
Unplug the board and take it from the pins on the socket that connects to the board, if you’re getting a high voltage you don’t want to do more damage.
WANTED 19 IN 1 PCB Please inbox me!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2019 at 9:09pm
Download the manual if you don't have a copy:

http://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/Space_Invaders_Service_Instructions_and_Parts_Catalog_(SV070019).pdf

Check the voltage pins on the CPU and Soundboard

i.e.

CPU
4 and D +5v
5 and E +12v
10 +18

Sound
1 and 2 +5
3 and 4 +12
5 -5

This is assuming you have a Taito boardset?


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Haves1979 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2019 at 9:48pm
Yes it's a taito board set and thanks for the manual. Thanks I'll remove the boards and take it from the pins.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2019 at 10:37pm
I have pulled the plug G and I'm getting 13.2 for the 12v point. The manual at point 6 says this can be adjusted but I cant see the board to do this, do you think this is because I have the cocktail or is it right down in the cabinet? Or is the power supply toast?

Cheers
Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purity Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2019 at 7:07am
If it is 13 without the board connected it is probably ok, because it will reduce under load.

The voltages can usually be changed on the power board.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 12:28pm
Hi All, I have been in conversation with Andy Welburn who believes that I have a ram issue on the middle board. Andy could repair this, however it would require sending to the US. Could anyone recommend somebody to carry out the repair, ideally in the North East of England? So far I have just found Williams in Pontefract.

Thanks in advance.
Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 1:06pm
Mark at Retroclinic is superb, he could help you.
Out of room but always room for one more !
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 1:11pm
Where exactly are you based?
You rang......?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 1:27pm
Sorry that would help!. I'm based in Newcastle upon Tyne.

Cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 10:39pm
Sorry that's a bit to far from me.
Would have like to come round yours and see if I could get it going for you.
You rang......?
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Haves1979 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Haves1979 Quote  Post ReplyReply Direct Link To This Post Posted: 15 May 2019 at 10:52pm
Thanks anyhow! I have had a reply from Mark at retroclinic and sounds reasonable, just need to get the boards out and posted off.

Cheers
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RaveN Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2019 at 12:50pm
Remove the roms and post a picture of the monitor.  If it's still the same as your first picture then it isn't (just) a RAM issue.
Welcome to bonus stage.
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