Zaccaria Galaxia arcade repair #4. Last PCB but still not easy.

[@taltechchip5827]

I enjoyed your video and very nice you found all the faults and showed every step in trouble shooting. Thank you

[@3vi1J]

Nice job! Thanks for sharing your insights and experience on those interesting faults.

[@HeyBirt]

The integration of hardware and software on these old boards in fascinating. It shows the skill of the engineer in understanding both subjects. A very long way from today when most programmers have no idea how the hardware works.

[@iz8dwf]

Hey Birt! Indeed the old arcade boards can be fascinating. There's actually also a quite substantial analog electronic part (on the audio effects board in this case) on most of them! I'm working right now on even older boards :) I just hope it won't take forever to fix them...

[@deborahberi3249]

Wow, removing eproms with just finger pressure is crazy. Never even thought to try that! Nice Video again. -Mark

[@iz8dwf]

Hi Mark! I showed that because a couple of them would actually slide out of the socket when I turned the PCB upside down and tapped it gently :)

[@RudysRetroIntel]

Excellent work and explanation of your diagnostics!! Thanks for sharing

[@rapiqui]

Excellent video as always. It's great to have such detail and explanation for every failure. It's not just a matter of replacing, it's understanding what fails and why, and you always prove it. Funny part of the video: the slow-mo aliens bomb dropping :)

[@iz8dwf]

Thanks for the nice comment! After working on a few similar boards, I could instantly spot odd things but I thought not everyone would see that the bombs didn't "move correctly" at their normal speed, so I tried to show the fault by slowing down the videos :)

[@RavenWolfRetroTech]

As always a very interesting repair.

[@marcopantanetti4053]

Good job Francesco and thanks for share as usual.

[@petesapwell]

Great work Frank, and thanks for all the explantations :)

[@iz8dwf]

Hi Pete! Thanks for the nice comment! Maybe in the future someone else will need to service one of these game boards and get some good hints from my videos, who knows :)

[@petesapwell]

@@iz8dwf that’s absolutely true, there aren’t many folk like us around anymore no need to keep secrets to ourselves, and of course we all need help with boards we’ve never seen before :)

[@NivagSwerdna]

Very good. I hope you didn't charge by the hour!

[@iz8dwf]

LOL!! A repair like this would be worth a retirement plan if charged by the hour :)

[@senilyDeluxe]

Boards that have been stored in a shed (ie humidity inside == humidity outside) for decades... I had an Amidar bootleg that took me an entire week while I was unemployed. My routine went get up - breakfast - continue fixing the boardset - dinner - continue fixing the boardset - go to bed - repeat. Still took me a week. About every 5th IC was bad. I also had to fix an Asteroids that had the same failure rate, but it started with a lot less bad ICs, they kinda failed while I was fixing it, keeping diagnose relatively simple.

[@iz8dwf]

@@senilyDeluxe Actually I don't think this one was particularly bad (other than the really bad socket disease). I had a video of a galaga bootleg with really bad fujitsu TTL. That was not stored properly too.

[@dl1gsn]

I think there is still an error on the board which is shown "back at home": When the top right aliens start to swoop down, there is a short "ghost flash" of an alien left of the alien field... or maybe that's just normal for these boards?

[@iz8dwf]

Oh I see! Well spotted indeed. I think this is "normal" on these boards. It is related to the S2636 PVI opack output that for some reasons needs to be delayed (watch the repair #3 for more details about that) so the CPU probably first programs one PVI to handle a diving alien, then erases the static alien from the formation. If the PVI doesn't correctly handle the bus termination phase, a glitch like this can happen. All is well as long as the diving aliens don't randomly teleport during the dive. Keep in mind that the original Galaxian game runs on Z80 and these boards use an S2650 CPU plus 3 x S2636 ICs that "handle" the diving aliens and sprite collisions of them. The code had to be ported to this new architecture. So I think these glitches are originating from both hardware and code imperfections.

[@SeanBZA]

Famous for the 74 dual flip flops to fail, changed so many of them over the years, easier to change it and see, even if a static test seems to show it works, they often fail at high clock speeds.

[@iz8dwf]

Well, I have the nasty habit of never changing something that hasn't failed :)

[@SeanBZA]

@@iz8dwf If there is one in a circuit area that is faulty that becomes the first suspect.