Astro blaster

[Lurch666]

Thought about using PCB way but never used the software so decided this would be simpler (albeit more work) than learning something new.
Will still build this since I've started but if this works would like to be able to use a smaller replacement that's the size of the chip it's replacing.

Yes it's just the one page.
It might turn out that it's not the VIC chip causing the issue so don't worry about making something better unless you enjoy the challenge.

 

[Lurch666]

Been slowly working on this but had a three week break.
It's now it's getting close to being finished.

 

[Lurch666]

Finished the VIC replacement board. Mixed results.

First I got nothing because I had missed one connection in the sync generator circuit.
After adding that I got the thick lines that normally appear on boot but nothing else. I think I have some dry joints because it's intermittent and now the picture (when one appears) is rolling. It's missing the vertical sync so need to investigate that part of the circuit.

But when I have had graphics appear I've seen proper text and some other graphics appearing properly. The enemy ships are messed up but that could be a separate sprite issue.

A bit of tinkering should get this board up and running properly and it's looking like the VIC chip was faulty.

I want to get this VIC replacement board working since I've spent so much time building it but ultimately I need to get a proper dual layer PCB made so it can be smaller and more efficient since I doubt I'm going to get my paws on a replacement VIC chip.

 

[TheDaddy]

Nice job mate ! I will say you are dedicated for sure , Not easy either !

Dave.

 

[Lurch666]

So it looks like I had a faulty LS393 at U5 as I found there was data going into pin 13 but no output from pins 8-11. Fortunately had some spare and now it's syncing properly and I have graphics.






There's still some issues with my replacement board so I'll iron them out and see what I get but it's much better output than I was getting with the original VIC chip.

 

[Lurch666]

Got the replacement VIC board fully working now.
The issue was a bad connection between the Board and the socket in the video PCB. I used turned pin sockets and pins so don't understand why I'm having this issue but if I press it in the correct place all the graphics are good.

Now need to look at making a smaller version of this. Any tips on how to make a gerber of the VIC replacement circuit I could get fabricated?

 

[bones]

Stopped using the turned pin sockets a couple of years ago now. Any chip you put in them you need to bend all the legs out so it's 2 or 3mm too wide for the socket and then wangle it in. I've had to revisit many pcbs where the chips are 'loose' in the socket.

 

[Lurch666]

Replaced the VIC socket with a normal socket and it's much better now.

Next (to put off the hassle of digging out a PSU that does -12V for the sound) I've tried removing the highscore kit and getting it to work with the original ROM baord.

I can get it to sort of work but only if I turn the voltage down to 4.2V.
The game runs (and for some reason the graphics are brighter) but when it gets to the astro blaster title screen and the text scrawl after that the graphics are corrupted.
This could be down to the decoder chip only partially working or some components not liking the low voltage. Checked all the roms,sounded out the sockets and all seem good so it's puzzling how it's only some graphics that are messed up.

 

[Georgian2]

You can have an standard 12V power supply for the -12v.
12V supply + to your other supply GND and the 12V supply -(minus) to the -12V input where is needed. The 12V supply must be isolated. Most smps are.

 

[Lurch666]

So I ended up getting a little converter board off ebay that takes +12V and outputs -12V.
I'm getting some sounds but no speech.
The sounds are all generated separately on the sound board so it should be easy to track which parts of that are not working using my audio probe.
Speech has it's own board and sorting that out is going to be more difficult so I'll tackle that first.

 

[Lurch666]

So I'm seeing activity in the speech circuit but unless speech is actually occurring It's hard to see if everything is working properly.
Tried slicing but was hard to get a sample while the speech was being activated so I switched to my scope to check inputs and outputs. I put my scope on a slow timebase so it would be easier to catch any activity.
I started around the 8035 at U14. Couldn't see any of the outputs of the LS139 at U10 going low but chip was showing OK when sliced but the only activity I could catch was on pin 2 so inconclusive.

Then I noticed an LS74 at U15 and I have had a lot of these fail before. I could see activity on the input pin 3 occasionally but nothing on the pin 6 output.
Quick piggyback and the speech returned. Not sure if all speech is there so will check once the LS74 is properly replaced.