Zaxxon PCB Repair

mattbert777

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Hello! I bought a Zaxxon PCB a few weeks ago on eBay in an untested state for a great price. I was looking to have a backup for a system I've been working on cleaning up/restoring.

Perhaps not unsurprisingly, the board didn't work and booted to some odd garbage on the screen. I was able to seemingly play it and plug it with a quarter. Poking around, I saw some references to replacing the video ram on it, so, ordered a couple of chips, put in sockets, and replaced it. The new video ram doesn't work well either, similar results.

I didn't spend a ton of time seeing if the system would play with the other video ram in it.

As I know this isn't necessarily the most popular game in the world and doesn't command huge prices in resale, I'm wondering what the best course of action is at this point- buy a working board or continue to tinker with this one. If I got the tinkering route, any suggestions on best place to start looking for the issue would be appreciated.

I'm attaching a couple of pictures of the garbage on the screen-- sorry they're not better.

I did hit the self test button a few times and could hear sounds in the background but nothing legible on the screen.

One thing- this board has NOT been recapped either.

Thanks very much!

mattbert
 

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First off, be careful. The traces on those Zaxxon boards fall off if you look at them funny.

You likely have a ROM problem, but did you check your power supply? The game has that weird multi-voltage power supply.

Look around 2012-2013 for my thread on a Zaxxon power supply. I explain what wires go where, which are used, which aren't and what you have to fix. It sounds like your power is good since you can hear the game running, but it could be something in the PS (high ripple).
 
First off, be careful. The traces on those Zaxxon boards fall off if you look at them funny.

You likely have a ROM problem, but did you check your power supply? The game has that weird multi-voltage power supply.

Look around 2012-2013 for my thread on a Zaxxon power supply. I explain what wires go where, which are used, which aren't and what you have to fix. It sounds like your power is good since you can hear the game running, but it could be something in the PS (high ripple).

Hello!

Thanks for your kind response. It's funny you mentioned the traces--when I put the socket in one of the traces had started to separate; fortunately it wasn't very much but was easy to fix.

I didn't check the voltages on the power supply yet, primarily because I have a working board in the cabinet so had assumed it was 'probably' OK.

That is a good point on the ROMs. I'm reticent to mess with my working board, but, I could pull the ROMs off of that and swap them and see if it makes a difference. If that worked, I do have a burner here so could buy a set of ROMs and burn new ones I suppose.

I'd be curious on your thoughts on the above approach. Thanks very much for your time! In the meantime, I'll check out the power supply thread, it definitely is a weird one!

mattbert
 
I'm a little concerned you have done so much work on the board. Every touch you make offers another potential problem. Most of the good people who troubleshoot look for the key problem, and then work the problem.

Have you looked at the Zaxxon troubleshooting guide in the manual? It may point you in the right direction.

The reason I mentioned the traces is I have prior experience fixing a Zaxxon in 2013 I think, and yes, I had the same problem. It was so bad I thought I'd lift traces if I looked at the board funny.

Since the game runs without video, I'd look at the video decoding ROMs and see if they are good or corrupted. Do you have a ROM reader?
 
I'm a little concerned you have done so much work on the board. Every touch you make offers another potential problem. Most of the good people who troubleshoot look for the key problem, and then work the problem.

Have you looked at the Zaxxon troubleshooting guide in the manual? It may point you in the right direction.

The reason I mentioned the traces is I have prior experience fixing a Zaxxon in 2013 I think, and yes, I had the same problem. It was so bad I thought I'd lift traces if I looked at the board funny.

Since the game runs without video, I'd look at the video decoding ROMs and see if they are good or corrupted. Do you have a ROM reader?
Hello!

Yes I do. The work on the board has been really minimal- just the two sockets and I did a nice job with them. Nevertheless, I understand what you're saying and never want to introduce new variables if I don't have to. I've done board level repairs for 40 years but am newer to the component-level things, although am decent-enough with a soldering iron, but, never want to get out over my ski's so-to-speak.

I'll get out the reader and check out the troubleshooting guide, and provide an update.

Thanks again! :)

mattbert
 
First off, be careful. The traces on those Zaxxon boards fall off if you look at them funny.

You likely have a ROM problem, but did you check your power supply? The game has that weird multi-voltage power supply.

Look around 2012-2013 for my thread on a Zaxxon power supply. I explain what wires go where, which are used, which aren't and what you have to fix. It sounds like your power is good since you can hear the game running, but it could be something in the PS (high ripple).
I've never experienced this.

the Zaxxon at work however, the large 1000 uf cap (I think) by the amplifier did in fact disintegrate the traces from leakage. lol

that one was also the first I ever replaced the caps and had issues with the explosion sounds not working after, necessitating that kind of obscure resistor mod for the caps to the op amps. that honestly should have been a separate article on my site. I think I found instructions or the explanation for it on a newsgroup post and then here. I believe those were the 2.2 uf caps, it's been about a couple years and thousands of missions since then and I can't remember every single thing I do anymore.

in other words, you don't want factory fresh caps to the op amps; they were intended to be kind of caca and have a delay.
 
I've never experienced this.

the Zaxxon at work however, the large 1000 uf cap (I think) by the amplifier did in fact disintegrate the traces from leakage. lol

that one was also the first I ever replaced the caps and had issues with the explosion sounds not working after, necessitating that kind of obscure resistor mod for the caps to the op amps. that honestly should have been a separate article on my site. I think I found instructions or the explanation for it on a newsgroup post and then here. I believe those were the 2.2 uf caps, it's been about a couple years and thousands of missions since then and I can't remember every single thing I do anymore.

in other words, you don't want factory fresh caps to the op amps; they were intended to be kind of caca and have a delay.

Thank you, and sorry for the slow response! Was away on a short vacation.
 
Thank you, and sorry for the slow response! Was away on a short vacation.

I'm a little torn on whether to try and track down an eprom programmer that works with the chips, or just buy a spare working board at this point and swap parts, which might be cheaper!

Thank you,

mattbert
 
I'm a little torn on whether to try and track down an eprom programmer that works with the chips, or just buy a spare working board at this point and swap parts, which might be cheaper!

Thank you,

mattbert
the GQ-4x4 isn't the highest quality programmer, but it is pretty versatile. it requires an external 9V transformer for some of the older roms, but I've found it makes programming more reliable for the ones that don't require it.
 
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