G08 driving me nuts!!!

CossackWarrior

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I just got this G08 back from a complete re-build. I plug it in and get this..... what is going on vector experts?????

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Pull out and reseat your XY boards.
Check for bent pins on the ribbon cable between the two.
Is the monitor plug connected to the correct pins? It could be shifted and/or upside down.

Yes, it is possible.
 
Well, they are keyed, so I figured they should be in correctly from the start.....but never know, I may have mixed them up. Also, one is short, the other is long, so I also felt certain that you can't mix the X and Y connectors up either.

Here are pics of them plugged in, and out:

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Looks more like a board issue to me. The vectors appearing at angles looks like part of a one porblem I was having with an XY timing board. I found the 2708 on that board scorched when I looked through the window after removing the sticker. After replacing that the angles started to be correct, but it still had other problems. I can't recall if I replaced anything else as well though when I found and replaced the 2708.

In general, watch out for the ribbon cable connecting the two xy boards.... it can be the source of all sorts of video issues. On another set, I replaced the two sockets with dual wipes and resolved issues.
 
Oh, one more thing.... I also had a set I was working on have random vector problems.... that turned out to be a marginal buffer chip (one of the ones close to the G80 bus) on either the xy timing or xy control. Different behavior than what you are seeing here, but flaky/marginal/bad buffers can cause all sorts of issues with the xy pair as well.
 
Ok so I think I may have found the problem or part of the problem. On one of the XY boards, one of the little chips (TL081CP)in the sockets, was totally corroded and had three broken legs. I can not verify yet, as I just ordered replacements.

What you pros think?

Two of the legs were broke off l, and two others on the verge.


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2,3,4,6, and 7 are the only pins used on the TL081. 1,5, and 8 are not. So, guess it depends on which pins. The TL081s drive the X/Y output, and you definitely had issues there, so once you replace that chip, you'll have to see how the behavior changes.

I've gotten tired of not having parts on hand, and have been working on Star Trek board sets lately, so I've purchased 10+ of some of the parts I had none of, or had short supply of.

The set I'm working on now had it's Universal Sound board creamed.... large spike on the +12V line I imagine, as every op-amp on that board was open or shorted. Two of the waveform generator chips were blown, and it still has problems. I suspect one or more DACs, as well as some of the XY switches. Whee, this one is fun :)

Good luck, let us know what happens when you replace the TL081. Its a common chip, you might want to see if there is a socketed one you could borrow from another board, or desolder form a junk board.
 
Typically if the op-amps are shot, you'll get no output on the X or Y axis. I think your issue is likely to be upstream of the op-amps, since it seems like the signal being applied to them is the issue.

It probably can't hurt to replace them, since TL081/TL082s are a very common failure on vector games, but I don't think it'll fix your issue. If you have access to a scope, I'd put it on the outputs of the board so you can isolate the issue to the monitor or PCB.

I wouldn't recommend using pulls unless you have a tester or are totally hard up for the part — they fail so often that the odds of pulling a dead one from your parts board is pretty high. If you own any vectors, you should keep some have TL081/2s on hand — most Atari boards use 4.
 
It's been suggested many times that the OP find a scope. He doesn't listen. LOL :rolleyes:
Easiest method to determine if its a logic board or monitor issue.
 
I agree with others are saying here, this looks like a board problem to me.

Do you have a scope? I'd use it as your monitor until you figure it out. Those boards are an absolute PITA to troubleshoot. That damn cage setup makes probing the boards a sucky deal.
 
FWIW, I recently fixed a Zektor board set that had a bad 161 on one of the XY boards. It too was drawing random vectors. Funny thing is that the chips were testing good on both of my TTL testers but one was bad for sure.
 
Ok, just switched the XY boards from a small spare working set I have, and I get the exact same problem. Could the problem be anything other then the XY boards?

Did I possibly connect the connector wrong:

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It seriously looks like a board problem. If you don't have a way to cross check (boards vs monitor), then others can confirm, but I think if you have an Atari vector, minus the power differences, you should be able to hook up the G08 to an Atari color vector to verify the monitor. IIRC the Sega's spit out a higher +/- V by up to avolt than Atari, so it should be safe to do... but don't do w/o others verifying my memory is correct.... I don't want to be responsible for the death of a G08.

But a scope is truly the way to verify the output from the boards.

If you have a pair that are known good, are you using the same interconnect cable when trying each set ? Are all your voltages measured good at the G80 bus ?
 
Yeah, that really looks like a board problem.

As mentioned above a working Atari vector game, or better yet, a scope would be of great help here.
 
BTW, if you do end up connecting that G08 to an Atari vector leave the G08 powered by your Sega cab and connect X, Y, GND, Red, Green, Blue from the Atari cab to the input of the G08.

It should work. Should.

YMMV and do at your own risk.
 
looked over the original posts.

I spy with my eye a Quantum that would have an Amplifone (if its factory). That monitor could easily handle the signals from Star Trek. Whatever's in that Lunar Lander could handle it too I'm sure.

At least you would know where your problem is. :)
 
looked over the original posts.

I spy with my eye a Quantum that would have an Amplifone (if its factory). That monitor could easily handle the signals from Star Trek. Whatever's in that Lunar Lander could handle it too I'm sure.

At least you would know where your problem is. :)

Lol, the Quantum is waiting on a tube, the Lunar Lander is waiting on a cap kit, but.....I do have another G08 that I am waiting on a few minor parts on to fix it that I can use later to help isolate where the issue lies.

Yes, VC I need more tools, a scope, etc, but I also need to take the time to learn how to use them. I want to, trust me, but I barely find time to fix all the issues my games have already.

Investigating further, I swapped more known working Star Trek boards I have, and I still get the same issues. For reference, here is a rough video I uploaded:

 
Both X and Y are effected in that image. I really feel like its a board problem unless some how the clamp board is to blame.

You are swapping out the two boards that connect together via the ribbon cable, right? Is the ribbon cable known good?

Hmmm....

BTW, you have sound problems too. I'm sure you already knew that though.
 
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