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Thread: Early '86 US Master System with very occasional graphic glitches

  1. #1
    WCPO Agent CrossBow's Avatar
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    Default Early '86 US Master System with very occasional graphic glitches

    So this is a console that has come back to me after I installed the Pause mod board and S-video into it a few months back. Tested fine here with several hours of burn in before I sent it back to the client. However, the client was getting some graphical glitches in a few games they tested. Here is what I've done at this point and found:

    I was initially unable to recreate the issue after several attempts to get it to happen. Finally had it happen late last night after I had the system on running demo mode of a game for about 4 hours straight

    This is the issues I've seen and were reported to me-

    - Moonwalker will have random white flashes that appear on the screen usually only on the first level of the game. It might be tied to controller movements but I can't confirm this. It appears to go away on its own after a bit or through use of the remote pause that was modded to the console using the two directions at once trick.

    - Columns will exhibit actual graphic corruption on the Timer display in the lower right corner section almost as soon as you start up a Flash mode of the game. However, this too doesn't happen unless the console has been on for a very very long time first. When this corruption happens, there are also occasional screen flickers that will briefly show corrupted graphics on the gems blocks. Also, I noticed that the down direction will not drop the block when this happens. But works normally again on the next gem block that falls.

    It is worth noting that aside from the down direction not allowing a Gem block to fall on the flash mode of Columns when the corruption occurs and the flicker occurs, that game play otherwise is fine. Also, in all instances if you start up a new game or reset the console afterwards, the issues do Not appear to come back.

    I at first thought caps might be blame as they were all original and I replaced them out the other day. So imagine my heart sinking when the issue came back late last night after the 4 hour burn in testing.

    My only thoughts are that the remote pause must have something to do with it so I'm going to disable that tonight and burn in again to see. I have the same pause mod on my personal SMS and have not seen anything like this. Also these issues I've described have so far only occured with Moonwalker, Columns and apparently it happened once on a game of Sagaia around level 3. But as the client was willing to send their Sagaia cart to me to test that, I can only work from Columns and Moonwalker both of which are my carts so that rules out the carts being an issue since both mine and the clients games do this on this system.

    Anyone ever seen anything like this and have another idea I need to look at? Since I can't make it happen at will and it is quite random I'm really at a loss as to where to look further?

  2. #2
    Raging in the Streets Blades's Avatar
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    I feel like you already checked, but maybe damaged traces, around a capacitor perhaps?

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    WCPO Agent CrossBow's Avatar
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    I have and didn't see anything out of the ordinary. But it was doing this before I replaced the caps and I only did that as I had read in other places suggesting caps to be a potential issue. Also if it were a bad trace, I wouldn't think it would take 4 hours for it to finally get warm enough for a crack or something to suddenly get wide enough. I would think it to happen much quicker than that.

    Again, the only idea I have for now is to remove the remote pause mod circuit from the mix since that is triggered by impossible controller combos. And yes, I do have diodes on each of the directions being used in addition to the +5 power to the pause circuit and also on the trigger output to the pause to make sure all the signals are isolated from each other. I will disable this circuit mod to see if anything changes and report back. My fear is that the main VDP combo ASIC is to blame as that is custom far as I know and the only way to replace it would be to pull from another SMS console.

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    Raging in the Streets Blades's Avatar
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    It's possible it's an IC, but I would do what you're doing right now and keep looking for simple issues.

    I had a full logic electronic tape deck years ago that would power cycle randomly. Sometimes it would work for hours, sometimes it wouldn't last a few minutes. Physical shock did nothing. It turned out to be a bad trace on the power line.

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    WCPO Agent CrossBow's Avatar
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    Well completely disabling the remote pause circuit that I added seems to only have corrected the flashing white screen issues with Moonwalker. The graphic corruption that only occurs in the Flash mode of Columns still happens after the console has been on for several hours. But like before, it doesn't actually lock up the game and just results in some controller oddness. But if you complete the current game or reset the console afterwards, it doesn't seem to come back? So this is very strange. Next on the list of things to try, is to remove the DC-DC switching regulator I installed and put a standard 7805 back into it and see if that makes a difference.

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    WCPO Agent CrossBow's Avatar
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    Wanted to add another update on this SMS. Honestly not sure what is going on with it. I've replaced the original 7805 into it as I had a DC-DC switching regulator in it as well. Added the pause mod logic circuit back in. Basically the white flashes comeplained about on Moonwalker I'm not able to recreate easily. Seems to be a very random thing. The flashes are just that...the whole screen will briefly flash white for just a frame. Graphics are not affected otherwise nor is the gameplay effected.

    I was now able to recreate this flashing screen issue though not as often or pronounced on my personal SMS with the Moonwalker. So my thought on this is that it is just something the game will do from time to time but only after an SMS has been on for literally hours. In the case of mine, it had been on for at least 6 hours solid when I noticed them. In the case of the one I'm working on it has to be powered on for about 3 - 4 hours before I've noticed.

    Columns is a different issue and I still can't figure out what triggers it. It only happens on the Flash mode of the game or Race track screen I guess to call it. The time graphic will glitch in the lower right corner of it within a few seconds of starting a game round. If you reset the SMS or play through the current round and start a new one, it doesn't come back? I'm not able to recreate this issue on my personal SMS and after installing a normal Vr into this SMS I'm not able to get the graphic glitch to occur as often and so I could fire up the SMS and it might immediately glitch up, or it might not do it until the SMS has been running for sometime playing a different game and then popping in Columns to play a round.

    At this point I'm going to have to kick this back to the client because aside from the main VDP and processor ASIC, I'm not sure what else it could possibly be? And the fact that it never seems to actually effect gameplay and is so random I'm lead to believe this is just some quirk of this SMS?

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    Raging in the Streets Blades's Avatar
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    Can you replicate the issue on an emulator?

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    WCPO Agent CrossBow's Avatar
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    Quote Originally Posted by Blades View Post
    Can you replicate the issue on an emulator?
    I haven't tried but since at least in the case of the white screen flashes on Moonwalker, it requires the SMS to have been powered on for a bit before they start.

    Well I tried last night to replicate the issues and they didn't occur on this SMS. I had it on for about 2 - 3 hours with moonwalker in demo mode. Started up a game and it played fine. I popped in Columns and still no issues there. I also wasn't able to replicate the issue in emulation but I'm not surprised by that as I don't think it is that normal for an SMS to do this on occasion and emulation is...emulation.

    Not a fan of random issues like this that can't be easily replicated. Wonder if this is some ESD damage to an IC in the system somewhere from the past? So strange...
    Last edited by CrossBow; 11-03-2020 at 10:04 AM.

  9. #9
    Raging in the Streets Blades's Avatar
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    Best of luck to you, sounds like you have a good handle on the situation.

    I suggested emulation because I thought it might just be a bug with the game.

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    Quote Originally Posted by Blades View Post
    Best of luck to you, sounds like you have a good handle on the situation.

    I suggested emulation because I thought it might just be a bug with the game.
    I agree and that was a good thought. But as the issue is so random it could be something specific on this SMS that is fine 99% of the time and only occasionally does this. I've told my client that I'm not really sure where else to go with it at this point. I can only occasionally get the issue to occur which, last night wasn't one of them. And it has only been noticed on the Flash mode of Columns, the white flashes in moonwalker (Now those are gone), and apparently it did some graphic corruption on 3D outrun when swapped to 2D mode and also level 3 of Sagaia it apparently did graphic corruption.

    Since my client was only willing to send me their columns cart for testing and it hasn't been easily reproducible, I don't know if what I've done will have an effect on the other games or not. I don't own any of the 3D games since I don't personally have the 3D glasses in my collection, and I don't own Sagaia. It was suggested I use a flash cart (I actually down't own a flash cart for the SMS as yet), but that isn't a good test either as I've seen games that won't work on a console normally, but will magically work when ran off a flash cart (Atari 7800 I'm looking at you...).

    So unless I can get a donor PCV where I at least know the VDP is 100% there isn't much more I can do to isolate and lock this down. I can tell you that I've never had an SMS in my house powered on as long as I've had this one powered over over the past 2 weeks in my work area trying to find out what causes this.

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