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Thread: Genesis 2: power on = black screen

  1. #1
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    Genesis 2: power on = black screen

    Picked up a Sega Genesis Model 2 with a 'VA 2.3 USA' board.

    The problem at hand is a black screen on power on both composite and RGB (official Sega RGB cable).

    Diagnosis so far:
    - receives power upon power on, voltage regulator functioning ok
    - caps looking good
    - traces to cart slot fine, cart slot cleaned, cart slot solder joints reflowed on underside of board. Wiggling the cart in the cart slot does nothing
    - mini din connector seemed fine but replaced for a new one

    Seems its a common issue, any other ides on what to check?
    Regards, MtothaJ

  2. #2
    Hollywood Hulk Gohan GohanX's Avatar
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    Pretty much my order of operations is check the PSU, check the voltage at the voltage regulator, reflow it replace the av and power jacks, check the reset switch.

    It the system was dirty when you got it also check the cart slot. Clean the hell out of it, and maybe try loading a game by putting pressure in various directions to check for worn pins. Also check the traces around the slot, I've seen a few systems that had Coke spilled through the cart slot that ate up the traces.

    Finally I'd look at the various chips, some of those smd chips had very little solder on them, there might be a pin that needs some more.
    Whatcha gonna do?

  3. #3
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    Thanks for that, reflowed the voltage regulator, power jack and reset switch and still not getting any signs of life. The console was pretty clean, there appear to be no components missing nor any previous repair attempts, all traces seem intact and no obvious cuts / discolorations on the board to investigate. I pinged the hell out of it with a multimeter in terms of continuity and all the tested traces checked out. Also tried booting up whilst applying pressure to the top of the various chips - makes no difference.
    As a last ditch effort I might desolder the cart slot to look for broken traces underneath but with Genny 2 prices being pretty low it make more sense to just buy another one rather than invest even more time into this one, when all the basic troubleshooting options have been exhausted.
    Regards, MtothaJ

  4. #4
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    Thierry Henry's Avatar
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    If you can, test it with Master System carts. If the system works in Master System mode then the fault could lie with the 68000. The 68K sits idle when running SMS mode.

  5. #5
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    I don't have any SMS carts but I do have a Sega CD - when connected with no cart inserted normally the Sega CD should go the bios screen. In my case nothing happens, CD does not initialize and still getting the same black screen.
    This for me kind of rules out the cartridge slot as the culprit. With this particular system its all the more frustrating since the system came really clean and in a nice aesthetic condition - there no broken traces, dirt in the cart slot etc. so there no obvious things to fix.
    Regards, MtothaJ

  6. #6
    H = Heinously
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    I've heard of the occasional Genesis system with a bad master clock oscillator. Without that, the console won't boot at all. I don't think anyone makes a 53.693175MHz oscillator though, might have to take one from another Genesis console.

  7. #7
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    I have a junk md2 va1.8 pal model i can use some parts from - I could try replacing the oscillator from that one. One thing I noticed is that the oscillators differ slightly between the two revisions: 1.8 uses the standard metal can style, the 2.3 uses one which looks more like an IC. That said the pcb on the 2.3 seems to be designed to accept both types, it has both outlines printed on the board and the additional 2 via's to accept the wider footprint of the metal can style oscillator.
    Last edited by MtothaJ; 06-11-2019 at 12:35 PM.
    Regards, MtothaJ

  8. #8
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    Its fixed!

    Its fixed! HMG's hunch about it being the oscillator was right. I desoldered one from a junk VA 1.8 PAL board and replaced the stock one on the VA 2.3 USA board and the machine fired right up.

    Below a pic of the VA 2.3 USA board with the oscillator replaced for the 'tin can' variant. The stock oscillator that crapped out is on the floor to the right of the board:

    genesis2.jpg

    So two takeaways:
    - the newer smaller oscillator and the older 'tin can' variant are interchangeable on a P&P basis
    - its sometimes worth keeping old junk to scavange parts from

    Many thanks for your help guys, happy that this Genesis 2 was saved from the trash can.

    PS. The NTSC 53.693175 Mhz oscillators are available on Ali - just ordered them and will replace for the correct one once they arrive:
    https://www.aliexpress.com/item/3275...AbTest=ae803_4
    EDIT: just received these oscillators and they work fine. Replaced in the Genesis II and also in a PAL HDG model 1 since 60hz is all I ever use.
    Last edited by MtothaJ; 07-01-2019 at 01:09 PM.
    Regards, MtothaJ

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