Asteroids Arcade PCB Repair (Again!) - Troubleshooting the "Watchdog" Circuit with Schematics ! 

Thanks Simon, we appreciate it!

That's very nice of you to say Doug!

That would be pretty funny, i'm working on another Asteroids PCB right now and man it is a tough one. Hopefully we'll get it running tomorrow :)

Love those sounds!

You can do it!

Harry I've always heard back in the day operators would burn through those transistors on the side (the deflection transistors) like candy until they figured out how the monitor worked and that they were expensive at the time....

@@LyonsArcade Yeah that was true but from an era where electronic repair of EVERYTHING was expected and MOSTLY done, these days, those kinds of repair are a niche market performed by a few specialists such as yourself. About 15 years ago an operator asked me to look at a faulty Daytona driving game, turns out someone had spilled a can of coke onto the logic board, I advised the operator to wash the logic board in warm soapy water and said "it's probably had it and even if it hasn't, the challenges of repairing a multilayered highly complex board is way beyond an oscilloscope and logic analyzer in a small workshop" the operator became abusive calling me a "...clueless idiot..." and saying "...I will send it to the professionals for PROPER repair..." I have to say, it was very satisfying to discover the PROFESSIONALS had returned the board with a note saying "beyond economical repair" some operators still think it's 1982 😁 Great channel dude.

Yeah some of them don't get it... there aren't even schematics available for Daytona. Super complex boardset too, likely one of the most complex ever actually. There's a guy at www.IRepairSega.com that can fix them, he used to be their tech at Sega and has the schematics and worked on them AT Sega so it's his specialty, but as you said a coke dropped on it (likely while it was on) even he's not going to be able to get THAT one going again.

by the way, I fixed a Stunt Cycle once, the old Atari Evil Knievel game... the manual in that basically tells you the entire logic setup, how each chip works, even down to some of the signals. I don't mean the schematics SHOW you, I mean they actually word by word explain the theory of the game. Very easy to troubleshoot because of that, but it was a much simpler time and board.

@@LyonsArcade Yeah Atari in particular were rather good at giving a circuit description which made things so much simpler. These days, there's no schematics and if there is one it's under licence costing an arm and a leg.

Thanks Darryl, we appreciate it, good luck with your repairs!

Thank you Mark we appreciate you watching!

There is... on the first version of the monitor for whatever reason something wears out and the dot shows up after it's been on awhile....

@@LyonsArcade The resistors in monitors have a nasty habit of changing value due to the heat causing some very weird issues furthermore the heat also screws around with the capacitors causing other issues. Out with the ESR meter for those, didn't have those in my day, in fact, you had a scope if you were lucky and a high impedance analogue FET meter, still got that just haven't got that heart to get rid of it 😁

Thanks Pete! Yes, you can send the outputs to a scope I did it on one of the Asteroids videos on here somewhere a couple years ago. These vector Atari boards use some strange voltages but you could probably test and repair them with an adjustable power supply with multiple outputs and a scope for video! Thanks for watching, we have more videos coming soon :)

@@LyonsArcade Hi Joe, Sorry if off topic, I have a Midway Space Invaders for repair! :) L shaped job. Game boots shows Hi score at top CREDIT at bottom, doesnt draw any invaders and then reboots... been on it for 2 days without finding anything...

That's true Clark, thank you for the info! Thank you for watching, have a good day!

Thank you Nico!

They put them in two places, look on the door close to the hinge, sometimes there's a little one there at the top of the door. The one inside by the volume pot isn't installed if the coin door is put on that has the switch on it....

@@LyonsArcade Thank you for the reply! You're right, it's just in a different place. I was thrown off by the black and white wire connectors that are dangling next to the volume control. Much appreciated!

It has to do with there being more stuff on the screen on the enter initials screen, so the brightness is different or something. You can turn it down to where the dot disappears, but it makes the screen really dim, we just live with a little dot.

Yes it's almost certainly bad, since it's only 'feed' is that 750khz clock and if that's accurate on a scope your outputs should definitely be there. It's also a counter, and they're known for dying, instead of just inverting a signal or anding/nanding whatever, it's doing math. Counters and decoders fail first, usually.. LS161's, 163's, 393's, 139, 138, all those are very common failures on these older pcb's.

@@LyonsArcade it’s crazy I forced the watchdog disable low and drag the probe around e5 and d5 (shorting between pins) and I’ve manage to get the board to run a few times but I have no idea what I’m doing to make it happen it’s total dice roll. I better set ot aside before i fry more chips. I’ll wait til i can replace b4

No big problems, just a lot of rain!