Yet another Astroblaster boardset repair thread

gamefixer

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Received a G80 (Astro Blaster) boardset from another KLOV user for repair today. Upon first inspection its booting to garbage although reset "looks" like its working.

Sure enough, probing reset at power up gives me a solid low for at least half a second then goes high. Clock signal is also good. A few data bus lines are driving higher than they should be.... Replace Z80a board now boots but game play but the screen is full of garbage.

Video board has some 4015's with broken pins. I've got more coming so I'll know more soon.

Will test I/O's tomorrow.
 
Continuing....

I swapped RAM into the video board from another set of AB boards so I can move forward. Game boots now but still looks bad. :(

After doing some poking about I come to find out that this custom IC replacement board is the culprit, and its undocumented.

I figured, what the hell, and started pulling ICs starting with the 74S151's in the center. ONE OF THEM WAS BAD! :)
 

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Test inputs with my custom card board control panel. They all work. I figured that I was in the clear now.

NOPE!

Missing three sounds and speech is nothing but while noise.

One cool thing about these older games is that the sounds are all triggered events rather than being generated by a sound chip. Makes it easier to pinpoint problems. I was missing player laser, enemy laser and player explosion. Looking at the schematics I can see that all three triggered events come from one IC and feed into another (Start at U33 and go into U26). I could see that the triggers from U33 were working on my logic probe but the output of U26 was not changing. Replace U26 and we now have our missing sounds back.
 

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Now to the speech board. I pulled the speech synthesizer IC and swapped one in from the other set, had speech. Ugh, synthesizer is bad. Nope, just bad contacts in the socket. Replace the socket and I now have speech but it gets garbled at the same point in the game every time. Hmm.. One of the data EPROMs must be bad. Sure as rain, U5 doesn't match the checksum against the MAME ROMs. Burn a new one, board now has full speech.

So long as the EPROM board is good then I think I've got this thing fixed!
 
Now to the speech board. I pulled the speech synthesizer IC and swapped one in from the other set, had speech. Ugh, synthesizer is bad. Nope, just bad contacts in the socket. Replace the socket and I now have speech but it gets garbled at the same point in the game every time. Hmm.. One of the data EPROMs must be bad. Sure as rain, U5 doesn't match the checksum against the MAME ROMs. Burn a new one, board now has full speech.

So long as the EPROM board is good then I think I've got this thing fixed!
Excellent job! Astro Blaster lives again :)
 
Now to the speech board. I pulled the speech synthesizer IC and swapped one in from the other set, had speech. Ugh, synthesizer is bad. Nope, just bad contacts in the socket. Replace the socket and I now have speech but it gets garbled at the same point in the game every time. Hmm.. One of the data EPROMs must be bad. Sure as rain, U5 doesn't match the checksum against the MAME ROMs. Burn a new one, board now has full speech.

So long as the EPROM board is good then I think I've got this thing fixed!
Quick question, Is there a way a switching power supply can be installed in a Astro Blaster? I don't think anyone has made a power supply conversion kit for Astro Blaster? Thanks
 
Quick question, Is there a way a switching power supply can be installed in a Astro Blaster? I don't think anyone has made a power supply conversion kit for Astro Blaster? Thanks

The G80 boards use +/- 5 and 12 so you could wire in an ATX supply.

VectorLabs sells an adapter that makes it really easy, http://www.vector-labs.com/index_g80pwr.html

Theres also an AC voltage that the board needs in order to run. You could probably supply that with +5 but I have not tried that so I dont know if it will work.
 
The G80 boards use +/- 5 and 12 so you could wire in an ATX supply.

VectorLabs sells an adapter that makes it really easy, http://www.vector-labs.com/index_g80pwr.html

Theres also an AC voltage that the board needs in order to run. You could probably supply that with +5 but I have not tried that so I dont know if it will work.

IIRC, the newer ATX power supplies dropped one of the voltages (looks like -5v ?) - so depending on whether I am remembering correctly, and which voltage, something might not work all the way.
 
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IIRC, the newer ATX power supplies dropped one of the voltages (looks like -5v ?) - so depending on whether I am remembering correctly, and which voltage, something might not work all the way.


Sure enough, -5 is missing from my bench ATX supply. I'm using a Vector Labs adapter and it looks like it get the -5 from the -12 source from the power supply.
 
My power supply is shot, Voltages are very low. I notice the only Voltages that can be adjusted are the +5 and +12, Bob Roberts have 2 types of G-80 power supply kits, Just ordered both kits.
 

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I'd be careful plugging boards into that supply until you get it worked out. Even without a load it should be able to come close to what it should be putting out.
 
I'd be careful plugging boards into that supply until you get it worked out. Even without a load it should be able to come close to what it should be putting out.
Thanks for the tips, I have the p.s. kit on its way and i'm also ordering vector labs G80 power supply board and buy a atx switching power supply...To be continued.
 
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