Robotron modifications ID

Stuffmonger

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So, I am doing some work on a friend's robotron board. I fixed up his jamma adapter, and his boardset works just fine. There are a few oddities, however that I would like to figure out the purpose to before I do any modifications to it.

The board is set up for jamma (I.E. the trace for video sync has been cut).
The battery holders have also been removed.
I am told it does not save scores (which doesn't surprise me knowing the batteries are gone).

Now for the mystery stuff:
on the cpu board, diagonally across from the battery holder area (top-left corner), a daughterboard has been added to the IC that is 3rd from the left on the top row. Daughterboard contains one IC (STK25C48-W45) and a part like in the pic (not sure what those are called) numbered 6A472G.

On the rom board, there is another daughter card installed in the bottom center IC. It has another part like in the pic, but yellow, and without a part number on it. It also has an IC numbered 74LS244N.

Anyone know what the purpose of these mods? Thanks in advance.
 

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So, I am doing some work on a friend's robotron board. I fixed up his jamma adapter, and his boardset works just fine. There are a few oddities, however that I would like to figure out the purpose to before I do any modifications to it.

The board is set up for jamma (I.E. the trace for video sync has been cut).
The battery holders have also been removed.
I am told it does not save scores (which doesn't surprise me knowing the batteries are gone).

Now for the mystery stuff:
on the cpu board, diagonally across from the battery holder area (top-left corner), a daughterboard has been added to the IC that is 3rd from the left on the top row. Daughterboard contains one IC (STK25C48-W45) and a part like in the pic (not sure what those are called) numbered 6A472G.

On the rom board, there is another daughter card installed in the bottom center IC. It has another part like in the pic, but yellow, and without a part number on it. It also has an IC numbered 74LS244N.

Anyone know what the purpose of these mods? Thanks in advance.


Don't know what the mod might be, but that component is just a resistor network.
 
Ok the stk part (Simtek) is an nvsram part. So the battery isn't needed with this mod.
 
Last edited:
The board is set up for jamma (I.E. the trace for video sync has been cut).
The battery holders have also been removed.
I am told it does not save scores (which doesn't surprise me knowing the batteries are gone).

Now for the mystery stuff:
on the cpu board, diagonally across from the battery holder area (top-left corner), a daughterboard has been added to the IC that is 3rd from the left on the top row. Daughterboard contains one IC (STK25C48-W45) and a part like in the pic (not sure what those are called) numbered 6A472G.

On the rom board, there is another daughter card installed in the bottom center IC. It has another part like in the pic, but yellow, and without a part number on it. It also has an IC numbered 74LS244N.

Anyone know what the purpose of these mods? Thanks in advance.

The daughterboard on the MPU board sound like an NVRAM board. It is supposed to replace the CMOS for saving scores and settings. Does it show the three reset lines on powerup?

The daughterboard on the ROM board was a factory engineering fix. IIRC, they initially laid the traces out to that chip backwards (it was fixed in later ROM boards).

ken
 
Now for the mystery stuff:
on the cpu board, diagonally across from the battery holder area (top-left corner), a daughterboard has been added to the IC that is 3rd from the left on the top row. Daughterboard contains one IC (STK25C48-W45) and a part like in the pic (not sure what those are called) numbered 6A472G.

That's one of my NVRAM adapters so it'll save high scores w/o batteries.

On the rom board, there is another daughter card installed in the bottom center IC. It has another part like in the pic, but yellow, and without a part number on it. It also has an IC numbered 74LS244N.

I've seen this mod a lot of williams boards for no apparent reason. It is stock, and it appears to just pull up the high address lines to a known state when the blitters are doing their thing.
 
That's one of my NVRAM adapters so it'll save high scores w/o batteries.



I've seen this mod a lot of williams boards for no apparent reason. It is stock, and it appears to just pull up the high address lines to a known state when the blitters are doing their thing.

I'll have to try it out at his place tomorrow. I wanted to know what the NVRAM adapter board was before I did a lithium battery kit on it. Glad I asked now. Hopefully, it works as it should. I had a feeling that this might have been a high score save chip, but wasn't sure.

Didn't know about the williams factory fix. I have 2 joust sets and a defender set, and none of them had it, so I thought it was strange.
 
Didn't know about the williams factory fix. I have 2 joust sets and a defender set, and none of them had it, so I thought it was strange.

Defender & Stargate didn't need it, they don't use the "special chips" (just DMA chips).

Robotron was the first out the door and they found the glitch after the first run of boards was either built or before they were populated. Rather than toss them and wait until they could get a fixed run of the boards, they opted to put a daughterboard on that fixed it. They then retrofitted the ROM board design and ran the corrected boards which were used for the rest of the Robotron run and the the full Joust run.

ken
 
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