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Toobin'

LittleLarrySellers

LittleLarrySellers

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This is on my grail list and was happy when I finally secured an "untested" main PCB.

After following the advice here, I got a basic JAMMA adapter going with the PWR and VIDEO which needed a 74LS02 to convert to CSYNC.

When I booted the board, I was happy to see the PCB red LED light came on and.... garbage graphics are what I got. I'll take it. It means at least my beginning of an adapter works and the board isn't totally dead.

In the garbled graphics I see a message that is listed in the manual as potentially bad RAM. I have a starting point at least.

Figured I'll keep a post about how this attempt at a repair goes since my Googling has returned almost nothing for Toobin'. Stay tuned and I am sure I will be asking for help at some point 8)
 

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Low hanging fruit was attempting to change the video RAM at locations that showed up in the garbled graphics. Luckily they are in sockets so I ordered some on eBay and swapped out the ones it was complaining about at 3E 4E/5E and progress!

I can see the attract screen now and the background waterfalls seem to be working correctly. Graphics are still screwy and I think saturated in red but step one was successful!
 

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Good progress!

I have an untested pcb set and original harness to setup for testing with JAMMA and so will be watching with interest.
 
I made some more progress on this repair.

There is no GREEN being displayed when I power on the board as you can see in the pics in the post above. Its saturated in red and blue colors. My first guess based on reading general repair logs and watching videos was to replace the palette RAM. I figured it was worth a shot and only $10 for some replacements on eBay.

And... NOTHING. It didn't do anything to fix the problem. WOMP. WOMP.

I spent probably a week or so after that poking and prodding with my logic probe and was really having a hard time. I even replaced a 74LS chip I thought was bad but it did nothing.

Then I thought since green was totally missing it was maybe my JAMMA adapter. I double checked continuity on the JAMMA adapter and my wiring was all good. This got me thinking what about the actual green output pin on the PCB. Since I checked literally everything else in the video circuitry.

I checked with my multimeter and the green pin was dead at 0V while the R and B were showing steady voltages (don't have an oscilloscope yet but this seemed to prove the issue all the same). I don't know why I never thought to check it before. I had always stopped prodding around the resistor array section. I never thought to look at the actual resistors and whatnot in that last leg of the greens journey to the Elysium Fields.

Well, it turns out this one transistor was bad. The emitter pin was dead and thus the green never made it past the transistor. Replaced the 2N3904 at Q7 and....
TbWPlba.png




HALLELUJAH! WE GOT GREEN!

aTguinw.jpg


I still have the weird graphical issues in what I believe are the "motion objects" per the schematics. I think this means the sprites. So that will be my next adventure but I am very happy that I have even gotten this far! 8o
 
Man this PCB is kicking my ass. I need some help now, gang, cuz I'm dealing with power issues way above my current understandings.

I secured the sound PCB which for these boards also houses the access to the test menu and the coin inputs so you really need it. Anyway, there is very limited stuff about Toobin'/JAMMA adapters on the Information Superhighway but what I did find said you could potentially use 12VDC to power the Sound PCB even though it actually requires 12VAC with the caveat that the sounds may be "off".

Well, off is putting it lightly. That iconic Atari coin-up sound effect? It sounds like water escaping from a frog's ass and all the music and whatnot is very heavily garbled. I did a recap already so I assume it's the lack of 12VAC causing the subpar sound quality.

Can someone advise me on how I can easily and safely send 12VAC to the sound pcb? I am not up to snuff on power design or this level of custom wiring. Can I use the existing 12VDC and safely convert it as per my pic below or do I need to do something more exotic? I read about transformers/step-up/down components but I'm not comfortable without getting some expert advice on how to do this. I'm using a Mean-Well RT65A btw to power my boards which obviously doesn't provide 12VAC.

Zp0UgzM.jpg



Thanks! And I still haven't figured out the motion object issues but am hoping the sound PCB is a easy win once I get the right power into it. Then I can go back to whatever the hell is going on with the sprites.
 
I wish I could offer a suggestion, but I've been needing a solution for low voltage AC power myself. If anybody has a way to do it, it would open up a lot of potential repairs on older and oddball stuff.
 
I am using a mean-well rt65a which only provides +/-5 and 12 DC through my JAMMA adapter I wired up. I don't have that original Atari PSU. Luckily the CPU board uses standard stuff so I didn't run into any issues with powering the main PCB.

I am sending 12VDC to the audio PCB where you highlighted above which works but it sounds like hot garbled garbage.

The question I have is can i take that 12VDC and safely convert to 12VAC (inverter/transformer or something. I am not confident on how this is done)? Or supply 12VAC directly to the sound PCB.
 
oh so you're missing that transformer

ps2.png



so the F3 and F2 2A fuses tells us you can uses a 12VDC / 2AMP transformer

somebody more knowledgeable than me should explain what 12vdc hi and 12dvc lo are ! X/ -12 and + 12?
 
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I have achieved proper audio! The iconic Atari coin-up sound effect and the groovy Toobin' soundtrack are now blasting in full effect.

Thanks @Mrhide for helping me understand the power schematics better. I did end up getting one of those 12V-0V-12V transformers rated at 2 amps per the schematics. This was way above my comfort level messing with AC voltage. I am comfortable with dialing in the 5VDC rail on my PSU that is about it. LOL

I would be lying if I said I didn't trip a circuit breaker on first attempt :cursing: but now I understand "center tapped" and how important that is to wiring up a transformer.

My JAMMA harness and 12VAC for audio are now done. Only thing left is figuring out the motion object issues.
 

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