Repairing a 1979 Atari Asteroids Arcade PCB 

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Glad I went back and watched an older video. Being a electronic hobbyist trying to learn more old digital stuff, I really enjoyed your troubleshooting. Good stuff!

Hey! I actually bought an original 1979 Asteroids cabinet from a nice guy in my area & your videos have been extremely educational on helping me repair mine. Unfortunately the cabinet I have has been gutted & trying hard to track down all the missing parts

thanks Joe, I like how you just plow thru all the systems and you have a good way of explaining the way the machine works. Props!

It amazes me, to see how large the components are in these old machines. I'm willing to bet, that's why they survive the test of time. I can't imagine a modern board lasting this long. Thanks for sharing this.

I'm not an electronics geek. I'm not a video game nerd... But, these videos are still fascinating. I guess it's that I like to see dead things brought back to life.

These videos are awesome! How come you guys don't have 1,000,000 subs?!?!?! Time to promote!!

Joe, I am working on an asteroids at the moment. Once the board get warm I start seeing lines jumping all over the screen. The board was repaired by an outside source, as well as the power supply. I just finished a cap kit on the monitor, but when it warms up the lines start jumping all over the screen.

Thanks love the ordinary Joe repair tips lol love all the repairs and nice job with the High Speed pinball my absolute favorite game.

I’m in the middle of fixing an asteroids myself at the moment and this is helpful. The memory test is all screwy. Game resets at weird times. And I had no Point of reference for the beeps. I need to go back and write It down!!

Learning a lot! Thank you man

I'm curious and going to try and see how many Arcade Asteroid consoles were sold since you mentioned it. I'm still a relative newbie to this channel. But this arcade game repair appears to be the most challenging one I've seen so far. But I enjoy watching how you're working through it.

Maybe DMAGO stands for Direct Memory Access Graphics Output? DMA is a way to access memory independent from the main CPU. There are multiple ways to accomplish this. For legacy CPU platforms, a common problem was how to use 2 processors with the same memory. Video is inherently a "client-server" type of situation. You have user code writing to the RAM and the video or video coprocessor reads it. For the Atari 800, they used a modified 6502 which added a halt line (/halt, or drawn with the line over it, active low). It works much like the /RDY line on the CPU, as that is used to suspend processing, such as when you need to provide wait states for ROM or slow RAM. The halt line differs in that it also disconnects the memory from the CPU. ANTIC is the video coprocessor. So the halt line suspends the CPU and disconnects the CPU from the memory. That allows another processor or device to use the memory without competition for the bus. And the video controller can even be a "dumb" device, like just a state machine that just keeps looping. All it needs to do at minimum is to read X amount of memory, send X amount of pixels, disable the video signal for about 1/4 that time or whatever at the end of each line, do all of that X number of times, then blank it for the equivalent of a scanline, then start over (at least for a raster monitor).

Hi Joe great set of videos you have made, I have been binge watching since I decovered them. I was a repair engineer for 30 years untill my health stopped me, your videos have brought it all back for me thanks. I must mention my understanding of a Watch Dog circuit. It is just a circuit that loops periodically and resets the processor, unless the code the cpu is running interupts the WD it will constantly reset the cpu. This is so if the cpu was to crash it would automatically restart the code because the cpu did not stop th WD in time. the WD circuit is usally only controled by the cpu and needs properly running code to function correctly. so if the reset is polling its is most likely because of the cpu not correctly telling the WD to sleep, either bad code or bad signal from the cpu.

So satisfying 😩

Again with the mystery music XD

41:52 I am an expert on this stuff, but enjoy troubleshooting videos anyway.

37:57 all that's missing is some ICs on a stick and we'd have ourselves a pretty good puppet show 👍

loads of great info. Thanks!!

When I need to lift a bug leg I put the chip into a spare socket then lift the leg on the socket then plug the socket with the lifted leg onto the board, as you do not bend the legs on the chip no broken impossible to find IC,s !

Scares the poo out of me when you go 'numbers station' on me like that.

One question: On a working asteroids board, what should pin 37 (watchdog) be doing? Toggling hi/lo? stay pegged hi? Stay pegged low?

Hopefully not to be annoying but whose logic probe do you use? Mine bought the farm and I'm looking to replace 😉

How do you verify the contents of the ROM's? Are 'images' of the contents available somewhere to compare against?

Great video!

JOE, If an arcade game board doesn't have a DMAGO to separate the video section from the CPU section, what signal do you disconnect the cut the board troubleshooting in half? Can you explain more what this DMAGO signal does or how it controls the watchdog circuit?

5:45 The Hyperspace button can be found at a random location out in space

And oscilloscope is definitely a good tool for troubleshooting when it comes to electronics just not video games you may spend a few bucks but you’ll save your time and you won’t bend any needles like with the old Votto meters so have a good day bye-bye

7:11 I wonder what happened that would cause the game to beep when you were using the multimeter.

Great video very interesting

Hey Joe, I have been watching all your videos in hope to figure out an issue that i am having with my asteroids arcade. My issue is that the PCB and the A/R are only reading about 2 volts. Definitely not enough power to operate. These reading were tested at the ROM chips, the attached grounds and +5's. I checked the original power supply as well and it appears to be working fine with appropriate levels. In the J5 wiring harness i am getting about 12-13 volts in 1, 2, and 3. Roughly 37 volts in 6 and 7, and about 7 volts in 8 and 9. Any help or expertise would be greatly appreciated.

37:24 I didn't know that you spoke a second language

Nice repair great job now move on monitor next ☺

24:10 the CPU has a few registers, so you could say it has like three bytes of RAM. (TL;DR) But you can test RAM even without that, all you need is ROM. Like, the code could say write 0x55 to the first address, read the address, test if it's 0x55 (so this test will fail if the ROM is corrupted because the value 0x55 is stored twice), if not goto error, then do the same with 0xAA. If the tests pass, you can use the first byte of RAM to store the counter for iterating over the rest of the RAM. But even the simplest CPUs have at least two registers plus accumulator, so you'll only ever need this knowledge if you decide to build your own CPU without registers and then write a RAM test for it...

BTW, it could be possible that if the crystal got knocked loose, it could be damaged internally. Just thinking.

21:00 uh-oh, LSD flashback

I have know idea why I had the two games confused. So my bad.

Dmago = “Direct Memory Access” go ????

Every come across a star trek arcade game?

Interesting, but for the love of Mike stop talking about how much easier it would be if you knew how to use an oscilloscope and spend a little time finding out how. It’s not like you have to spend a vast amount of $ these days in buying one, and once you have the basics down (which aren’t all that complicated, it’s basically voltage vs time, and when to start recording) then half the job is done. The other piece of (very cheap) kit to consider is the logic analyser. These can be had for not much more than your logic probe, and will tell you things like what is coming out of a chip vs what is going in, what frequency the clock is running at, what data is on the data bus, what addresses are being generated on the address bus etc. Basically much of the time you can find out which chips are bad without desoldering and replacing them.