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jmetal88

Flickering Pixel. Bad RAM?

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I've got a question for those who are knowledgeable about the inner workings of the Lynx.

 

My Lynx II has had a flickering pixel ever since I got it. I thought it was an LCD problem. But I've just installed a McWill LCD, and the exact same pixel is still flickering.

This obviously indicates the problem was NOT with the LCD, but is on the main PCB somewhere. So, if any of you are Lynx hardware experts, where do you think the failure lies here?

My suspects would either be one of the RAM chips or Mikey. Obviously it would be easier to replace the RAM chips (and I have the equipment/skills required to do so) but I'd like some

confirmation that that's where the issue would most likely lie before proceeding. I have a feeling if it turns out to be Mikey I'd be better off just getting a replacement Lynx (unless anyone

knows where I could get a Mikey chip by some chance). So what do you think? Replace RAM, or go ahead and look for a new Lynx?

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Well, I thought I'd try swapping the RAM chips with each other just as a preliminary test. The results are odd. I have a flickering pixel in approximately the same location as before (although I think it may be one line lower due to the fact that it appears much more obvious in the title screen), but I now also have a second flickering pixel on the same line. I think that means the RAM chips are contributing to the issue, but I'm not 100% sure. I may have to swap the chips back for a sanity check.

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No, I swapped them back and it looked the same... I guess I never really noticed the second one before because of the horrible contrast on my original LCD. So I guess I have a bad Mikey.

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If I'm not mistaken, Best Electronics sells the chips??

 

I thought they did, too, but I was looking on their site and didn't see it listed.

 

I decided to take my chances with one of these:

 

http://www.ebay.com/itm/Atari-Lynx-II-2-System-Console-for-Parts-Repair-DEFECTIVE-NO-RETURNS-NON-WORKING/382100414619?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

Hopefully it won't also have a bad Mikey.

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They don't list everything. It's best to email or call them with a list of needs and they'll let you know.

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I'll do that if I can't get what I need out of that broken unit. But I'll see if that can help me first.

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It cannot be a RAM issue if its always the same pixel. The games use typically different screen addresses.

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Let me know if you do find any new Mikie chips! It's very odd - I would expect if there was a RAM issue that the system wouldn't work with some games (well, maybe a crash at the point when the RAM is used). EDIT: nvm, I see Mikie is more likely.

 

EDIT: Have you considered that maybe a passive is a problem somewhere? eg. a cap or something? What's strange about this is if the pixels are in specific screen locations - it's strange and would lead me to think there's a timing related glitch occuring under certain circumstances. Do you see the same pixel pattern with a variety of different games, or does it shift or change in any way?

 

Looking at the connections from the LCD to Mikie there I see a few places I would be checking to rule them out. eg. CLK3. DBL - not sure if that's solely responsible for power of the screen or what. And I would certainly check each of the connections between Mikie and the screen to make sure you've not got corrosion, some contaminant over a couple of traces etc, and around Mikie itself. There looks to be resistors or inductors on the connections going from Mikie to the LCD - maybe you've got an issue somewhere on the PCB rather than a faulty Mikie.

Edited by GadgetUK

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I don't think it would be anything passive if it's always the same pixel... Passive issues like cracked solder joints, bad capacitors, or corrosion are typically either random or they affect everything on that particular trace.

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I will try a couple of different games this afternoon, though. I mainly just play Chip's Challenge, but I also have Pinball Jam and Todd's Adventures in Skills Slime World I can try out.

Edited by jmetal88

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I don't think it would be anything passive if it's always the same pixel... Passive issues like cracked solder joints, bad capacitors, or corrosion are typically either random or they affect everything on that particular trace.

I've seen wierd impedance problems where a trace running next to another trace can cause repeatable behaviour almost at the same point each time. Although if that were the case I wouldn't expect it to be the same all the time - it would probably have some variation. Have you tried heating and cooling mikie - eg. get some freezer spray onto it, or hot air dryer - to see if anything influences behaviour. Where abouts on the screen does it appear - that could be a clue too.

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It's toward the bottom of the screen. On Chip's Challenge, it's right below the bottom of the 'A' in the title screen.

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(Forgot to mention the other pixel is on the same row, but toward the left side of the screen.)

 

Well, on my other two games, I can't see the flickering pixel toward the middle of the screen, but I can still see the one on the left side of the screen, and it is still in the same location. But, sometimes it flickers, and sometimes it doesn't, and it seems to be related to what's being displayed on other parts of the screen. It's like Mikey is getting intermittently confused and trying to render a pixel from elsewhere instead of the pixel that's supposed to go there. So if the two that are being confused are the same color, there is no flicker, but if they are different colors, it flickers between the two.

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Also possibly of note, the pixel at the left edge of the screen behaves normally during Chip's Challenge gameplay, and only the one toward the middle of the screen flickers then. Which is also kind of odd, since that's the opposite of what the other two games do. The only place I've been able to see both flicker at once has been the Chip's Challenge title screen.

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I was playing Chips challenge the other night and I have a pixel in the lower left that flickers as well. I have the McWill screen in my Lynx II also and thought it was a screen issue. Played a different game off of my Lynx SD cart and see no flickering pixel. Assumed it is the game Haven't looked into it any further. Might have to now and see if Chips Challenge has the same flickering on my Lynx I with McWill screen and stock Lynx II.

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Just made some testing, Lynx I and II with McWill and original Display.

No flickering pixels with Chips Challenge, title screen or during game.

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Not flicking on mine either, although I am using the original firmware - not sure if anything critical changed other than the scanlines mode he added later.

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Also possibly of note, the pixel at the left edge of the screen behaves normally during Chip's Challenge gameplay, and only the one toward the middle of the screen flickers then. Which is also kind of odd, since that's the opposite of what the other two games do. The only place I've been able to see both flicker at once has been the Chip's Challenge title screen.

What about other games? You might be chasing a ghost! I wonder if it could be there's two versions of this game or something and maybe one glitches on title?

 

EDIT: I am also wondering about chip revisions too - maybe its related to the version of Mikey on that PCB, and note there are a couple of different board revisions.

Edited by GadgetUK

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What about other games? You might be chasing a ghost! I wonder if it could be there's two versions of this game or something and maybe one glitches on title?

 

EDIT: I am also wondering about chip revisions too - maybe its related to the version of Mikey on that PCB, and note there are a couple of different board revisions.

 

I don't think you quite understand what my last few posts were trying to convey, so let my try to give a better explanation:

 

On my Lynx, there are two pixels that flicker. Both are toward the bottom of the screen, maybe 8 rows up from the bottom. Left-to-right, one is near the left edge of the screen, and one is near the center.

 

These behave differently depending on which game is running and what's being shown on the screen. On the Chip's Challenge title screen, both pixels flicker, but that is the only condition under which I've seen both flicker.

 

During gameplay for Chip's Challenge, only the pixel toward the center of the screen flickers. I have also tried two other games, Todd's Adventures in Slime World, and Pinball Jam. On both of these, the pixel toward the center of the screen does NOT flicker, but the pixel toward the left side of the screen DOES flicker. In either case it is the same two pixels (they do not move around the screen), it just depends on what is being shown on screen as to whether one, the other, or both (or neither, in some cases) will flicker.

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Well, I got the broken Lynx in and the results are interesting. I replaced Mikey first, of course, because that was my main suspect, but that didn't help and I had the flickering pixels in the exact same spots. So I thought, however doubtful I was, that I should attempt replacing Suzy next. And replacing Suzy fixed my issue! So yeah, any of you looking at a similar flickering pixel issue, apparently Suzy needs to be on your list of suspects.

 

Makes me glad I went with the 'broken Lynx' route instead of tracking down a Mikey specifically, because if I had I would've had the wrong chip and no other options to test with.

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Glad you sorted it, and thanks for sharing the result =D Thinking about it, it must be related to the blit process, perhaps something that Mikey doesnt handle. (EDIT: Thinking about it I know it doesn't - Suzi will be doing the blit, so maybe Suzi has a glitch occuring at certain point in time which results on that pixel issue). But Mikey does seem to drive the screen, so quite unexpected!

Edited by GadgetUK

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Well, I got the broken Lynx in and the results are interesting. I replaced Mikey first, of course, because that was my main suspect, but that didn't help and I had the flickering pixels in the exact same spots. So I thought, however doubtful I was, that I should attempt replacing Suzy next. And replacing Suzy fixed my issue! So yeah, any of you looking at a similar flickering pixel issue, apparently Suzy needs to be on your list of suspects.

 

Makes me glad I went with the 'broken Lynx' route instead of tracking down a Mikey specifically, because if I had I would've had the wrong chip and no other options to test with.

Really hard and nice fix... Bravo!! :)

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Ha, I installed the defective Suzy (along with my old LCD) into the broken Lynx just for kicks, and yeah, my flickering pixels followed the Suzy.

 

(I just thought it would be a nice confirmation that some other disturbance on the board during my chip replacements didn't have any effect on the issue.)

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