Whats really inside a Sega MC8123?

Dead Perfect Billiards MC8123A donated itself to science.

Desoldered the aluminium cover and bottom little pcb and magically appeared a black NEC MC8123A.

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Apply some heat at the plastic ‘tub’ peels off.
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Apply some more heat and the potting mix turns to rubber and can be chipped/peeled away to expose the little ceramic pcb holding the battery and a 3771 reset chip.

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The bottom still has potting mix intact, so more heat and chipping away with a screwdriver reveals this.

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Unfortunately the solder holding the legs on melted and they came off. All thats left is a ceramic pcb with what’s probably glob tops.

Unfortunately I don’t have the chemicals to dissolve this stuff and heat doesn’t seem to do anything to it.

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I wonder why there are 6 solder points on the top of the pcb? Maybe a way to program the MC8123’s encryption ram?

Sega Outrun… Or is it?

I brought an Outrun pcb which looked original from the auction picture. It even had the Sega licensed holo sticker.

Nice holo sticker

But but when it arrived, it looks like a bootleg.

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Back in the 80’s it was expensive to import electronic equipment (tv,etc) to New Zealand so many companies just imported the parts and manufactured them locally. In other words Taito NZ most likely brought the custom chips (including the ck5205 chips), from Sega and built them. Hence the ‘Manufactured under license sticker”. Oh, and thanks guys for soldering in all the eproms.

Original pcb for comparison

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Edge connectors and interconnect cables are better though.

 

IREM X-Multiply repair log

Another great horizontal shooter from IREM.

Very low volume was the first issue. Checked the volume pot as it had been changed. Was the correct value. Replaced the 1000uf capacitor that was visibly bulging and the sound came back very loud!

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When it is first powered up all the ROMs and RAM 7 show as bad, but powering the game off and on again reports RAM OK ROM OK.

Left for a few minutes it doesn’t again.

Having already replaced the capacitor which was bulging, the rest of the capacitors were suspect.
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M72 games have a reset chip at ic7, with two timing capacitors. Shorting out both when the board was powered off produced the same error message every time. Replaced both capacitors at C8 and C10 got the board reliably booting.
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Reverse Engineering Robotron on a bootleg Defender pcb.

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This little pcb was created by Radich Electronics back in the day to convert a bootleg defender boardset into a Robotron boardset.

But where is the Special chip 1 pair you say? All the TTL logic above the roms implement the blitter chips. In a attempt to prevent copying they have sanded off all the identifying labels.. even underneath the chips!

Fortunately nowadays we have chip testers that can identify any TTL chips, so I am currently labourously desoldering and identifying each chip. Next step is to scan the pcb and make a net list to create a schematic. There are tools out here to assist with reverse engineering but they are all expensive, or require paying someone else to do the work.