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Thread: Sega MD2 VA1.8 Black Screen Issues

  1. #1

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    Exclamation Sega MD2 VA1.8 Black Screen Issues

    As above, experiencing a black screen when powered on as if there was no cart inserted. No sound, no nothing. Black Screen.

    1. First off, I tried cleaning the slot. Cleaned it real good with contact cleaner. Still the same.

    2. Checked the continuity on each pin to the solder points. Again, fine.

    3. Checked the obvious of bad caps and resistors both visually and with the multi across the board. All seem good.

    4. Checked the voltage of every IC on the board, again, nothing odd there.

    5. Decided to change around my leads just to see. I tried RGB Scart, AV Composite and RF. All the same. So that to me rules out an actual video issue, on top of actually getting a black screen and my TV displaying a signal.

    I have a working VA1.8 here too ive been using for reference and everything ive checked so far looks good.

    Now, from searching from this forum and others. Its looking like a RAM issue. Possibly the z80 cip? As apparently this checks with the cart before a POST and wont go any further until it does?

    Is there anyway I can test this further to confirm?

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    Raging in the Streets Thunderblaze16's Avatar
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    Pics of the board my good sir.
    ***Visualshock! Speedshock! Soundshock! Now is time to the 68000 heart on fire!***
    http://ban-game-4.gamewise.co/musha-metallic-uniframe-super-hybrid-armor_banner65-61867-full.jpeg

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    Quote Originally Posted by Thunderblaze16 View Post
    Pics of the board my good sir.
    You wont see anything worthy with my potato of a camera unfortunately!

    The board is spotless tho, console has always been stored in a bedroom wardrobe so never exposed to any damp / moisture in an attic or basement etc.. So zero corrosion present, no clear signs of bulging caps, bad traces... burn marks/smell. It literally looks like its rolled off a production line.

    Is there anything in particular you suggest checking?

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    Road Rasher
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    If it displays the 'Produced by or under license from...' screen but then dies at a black screen right after, it's (often) a Z80 communication failure (usually Z80 RAM).
    If it doesn't even display anything at all, it could be one of a much wider variety of problems. 68000 work RAM would be one (unfortunately rather common) suspect. I believe the VA1 and later use a single Sanyo LC331632M or equivalent 32K x 16-bit 120ns DRAM. Unfortunately the RAMs are SMD so unless you got some SMD removal alloy or a hot air rework station on hand, repair may be a bit difficult.
    In very rare cases the 68000 CPU is fried.

    One way to test for 68000/work RAM related problems, would be to try playing a Master System game on it using a Power Base Converter (you may have to remove the top shell to get it to fit). If the SMS game starts up, then we know the Z80, Z80 RAM and VDP and its RAM are likely okay, and not part of the problem.
    Last edited by Eep386; 02-08-2018 at 10:39 PM.

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    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert
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    I've often found in my experience of this particular board revision, that it is the most finicky. Every single 1.8 I have had that I have overclocked has exhibited problems with crashing or games not booting, just from having the stock clock signal run through a switch rather than directly to the clock pin.

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    Road Rasher
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    Haven't noticed many problems with the VA1.8 personally, aside from the crappy sound and usual tendency toward having the awful KA2195D encoders. Fortunately these consoles accomodate a CXA1145M or MB3514 with very little fuss, once the needed parts are added.

    For me however, my problem console is the VA2.3. I have a bit of a love-hate relationship with them; the VA2.3s with the 315-5786 VDPs (aka. the VA2 VDPs) are rarely problematic, though I've run into a few defective ones (that were obviously badly abused). However, I ran into a fair number of VA2.3's with 315-5685 VDPs that have an odd 'off-by-one' glitch in their shadow/highlight register implementations, where the shadow/highlights start one pixel to the right of where they normally begin with other VDPs and systems.

    (dives into a nearby trench)

  7. #7
    Hedgehog-in-Training Hedgehog-in-TrainingWildside Expert
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    I couldnít possibly comment, Iíve never come across a VA2 or 2.3. I do live in the UK though, so I donít know whether certain revisions didnít make it to the PAL region or what. Iíve never even seen a VA0, VA1 or VA1.8 with the crappy KA2195D encoder, Iíve only ever seen the Fujitsu. As I said Iíve never seen a VA2 or VA2.3, or even a VA3. I was under the impression that the VA4 didnít make it to Europe either, until recently when I got a hold of one, and I am to understand those things are like gold dust. Interestingly enough though, my VA4 doesnít have the Sony encoder like others do, it has a Rohm BH7236AF.

  8. #8
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    Interesting, the BH7236 looks like another CXA1645-alike. It can do either NTSC or PAL.

  9. #9

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    I'm having a similar problem with an NTSC VA1.8 I just picked up. On the bottom of my board, a bunch of the diagonal solder joints around the edges have been eaten back to just the copper. I'm not sure what did it (cat urine?) but I get a black screen. The voltage regulator gets warm while it's on, the power LED turns on and I can probe 5V at the middle pin in the cartridge.

    The motherboard looks a little bowed in the middle, but all the pins make contact (verified with continuity). I tested with a few different (freshly cleaned) games.

    There look to be some small corrosion issues around some of the pins from the RAM chip to the cartridge, but continuity testing says they're okay once I cleaned them up with isopropyl alcohol and a toothbrush. I also tested all the wipers to make sure they retract and expand as you'd hope.

    No sound, and although I don't have a logic probe, nothing much seems to be going on with the other pins on the cartridge slot either. I'm guessing it's stalled reading from the cartridge, because its behaviour is identical to when you don't have any cartridge inserted.

    I'm not terribly familiar with the Genesis motherboard, as all of mine have always worked up to this point One thing that is odd is that the clock crystal seems to have a bit of masking tape or paper or something sticking out from under it, which I haven't been able to dislodge with tweezers.

    The machine itself is definitely filthy. A dead fly rolled out while I was pulling the RF shields off.

    Attachment 13885

    Attachment 13886

    imgur link, in case the attachments break: https://imgur.com/a/drdb7

    I put some solder on the bare pads on the expansion connector, but that was pretty much out of frustration.

    I might grab some more pictures of this with a better camera later - any specific areas to focus on?

    Update: I don't think it is the cartridge slot though it was definitely filthy. I tried connecting a Sega CD 2 to it, but that just made a black screen with a static hiss or loud continuous tone at best.

    I'm getting ~12V at the input rail on the power regulator, and ~5V out of the regulator, with 5V sampled throughout the board. I reflowed the cartridge connector pins as well.
    Last edited by seat safety switch; 02-23-2018 at 01:07 AM.

  10. #10

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    Update 2: I realized the top-side trace from pin 36 of the RAM was not continuous with the VDP. I soldered a crappy patch wire (an resistor leg) after scraping back the corroded trace with an x-acto knife. Now it gets to the "Produced By" screen, and then goes to a black screen (which is indicative of cart-slot troubles, in my mind).

    See pictures above: it's the first of the 'corroded' traces. The via immediately below it, which I think is pin 35 on the RAM, is continuous with both the VDP and the cartridge.

    If I plug it into a Sega CD with no cartridge inserted, the Sega CD seems to act normally, but the BIOS screen never comes up properly - it comes in fits and starts, with a static burst and then a glimpse of a few of the brighter pixels of the "globe" and logo. I haven't yet tested if it can read a CD game, because there's probably no point.

    My cart slot is not in great shape since I've been ham-handedly "re-tensioning" the pins: one of them seems to spring backward now, instead of forward. I might mess with that some more. The corrosion on the topside seems limited to only those pins near the RAM, so I don't know how it would affect the Z80 (which is much more southerly). I also don't have a Power Base Converter to test, so it's fairly academic.

    Update to the update: I messed around with the cartridge pins for a bit more and got lucky. Now I can play games perfectly! Another Genesis saved from the landfill.
    Last edited by seat safety switch; 03-01-2018 at 07:39 PM.

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