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View topic - WTB: SEGA SC-3000 MITEC IC

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  • Joined: 10 Oct 2022
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WTB: SEGA SC-3000 MITEC IC
Post Posted: Mon Oct 10, 2022 9:17 am
Hi All,

Have a Sega SC-3000 (AUS version) I'm trying to fix and believe the MITEC IC has failed.

Anyone know whee I can get one or have one to sell?

Thanks

Sonny
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  • Joined: 14 Aug 2000
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  • Location: Adelaide, Australia
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WTB: SEGA SC-3000 MITEC IC
Post Posted: Tue Oct 11, 2022 1:52 am
What's the system doing that makes you believe the MITEC chip has failed son?
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Post Posted: Tue Oct 11, 2022 2:50 am
Hi,

Well, I have someone with a good MITEC chip and when installed - the machine boots but the graphics are a bit garbled. With the original MITEC installed the machine will not display anything so figure it's the MITEC?

The Sega got dropped some time back and we've been in the process of trying to fix it. The next step seems to be replacing the MITEC and then working on the garbled graphics as I think a few tracks could be broken.

Have you got any ideas that might help?
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  • Joined: 14 Aug 2000
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WTB: SEGA SC-3000 MITEC IC
Post Posted: Tue Oct 11, 2022 7:01 am
The fact that you had another chip to swap in and try is remarkable.

I’d start by checking the power rails, clock and reset circuit if you haven’t already. Likewise with cleaning and checking the cartridge slot connector.

The MITEC chip generates the Chip Select signals for the PSG, VDP, PPI, SRAM and Cartridge Slot (/CE89, /ROM_CE, /CSRAM, /MEMR, /MEMW, /IOR, /IOW, /CSW, /CSR). Grab the schematic and test these for continuity.

If the above all checks out, then we’ll need to go deeper into the fault finding.
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  • Joined: 26 Feb 2021
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Post Posted: Fri Oct 14, 2022 8:05 pm
Does that chip fail often?

If so it would be worth reproducing for preservation. I can do it but I don't have access to any piece of hardware using one.
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Post Posted: Fri Oct 14, 2022 8:33 pm
Seems they do fail on a regular basis and are impossible to find replacements as they haven't been produced by Sega in many years. Building a replica would be fantastic but it need someone to reverse engineer the logic right?
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Post Posted: Sat Oct 15, 2022 3:40 am
It does look like it would be easy to make a clone in programmable logic, and most of the function can probably be guessed from Enri's schematic.

I think only the /MUX signal isn't obvious from the name and context...
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Post Posted: Sat Oct 15, 2022 4:13 am
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Seems they do fail on a regular basis


@macsonny what is that based off?

I don't recall anyone ever posting that they had a failed chip.

When you swapped in a chip from a working console, you went from a non-functioning console, to a non-functioning console. Seem like you have other issues with the unit.

@everyone else, the schematic and timing diagrams are in the official sc-3000 service manual.[/quote]
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Post Posted: Sat Oct 15, 2022 9:47 pm
macsonny wrote
Seems they do fail on a regular basis and are impossible to find replacements as they haven't been produced by Sega in many years. Building a replica would be fantastic but it need someone to reverse engineer the logic right?

I can do it, I have reversed much bigger/complex chips before.
Upon a quick look at the pinout and with some educated guesses most equations can already be deducted.
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