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Just got an Apple ][ plus and need to replace ROM D8

D

dafivehole

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One of the legs is broken off... its got "3410012-00 Apple78 D8" on the top of the chip. I'd like to replace it with the exact same chip in an effort to keep it as original as possible... anyone know where I could get one of these? Nothing on eBay...

Thank you,
Roger

View attachment 15599
 
I have to agree with NeXT for a bone stock original you are probably going to have to fix that one.

But since its just a ROM, if you just need functionality, you could just burn the ROM to a more modern and obtainable EPROM/EEPROM part.
 
Sorry to necropost, but I also have a defective D8 ROM and would like advice on how to obtain a replacement or burn an EEPROM with the ROM data.
 
Can an Arduino be used to burn an EEPROM? Also, what kind of EEPROM would be compatible?
 
Could I use an Arduino to burn the EEPROM? Also, what EEPROMs would be compatible?
 
Hello Ivoah,

I don't know if you can use an Arduino to burn an EPROM.
But here is a link regarding the ROM replacement.
 
Warning: EPROMs are not compatible when a language card is installed on the Apple II, even with an adapter. They don't support the "inhibit" function of those masked ROMs.
 
rittwage said:
Warning: EPROMs are not compatible when a language card is installed on the Apple II, even with an adapter. They don't support the "inhibit" function of those masked ROMs.
Click to expand...
This sounds very wrong! And btw these apples were designed initially with EPROMs, weren't they? ;
 
The inhibit line is used to keep the ROM on the motherboard from responding to a D000-FFFF address. It can be asserted by a peripheral card (like the language card) that wants to use that address space. This line is connected to ROM socket pin 18 and is brought low to disable the ROMs. Even if you rewire the enable of a 2716 with a stacking socket, you still need to connect the inhibit, which is effectively a low disable signal, which doesn't exist on a 2716. You can hack together a solution by adding an inverter to the inhibit line, making it effectively a high disable signal which could be tied to a 2716 enable input. There is an example on my web page.

http://www.willegal.net/appleii/appleii-integer.htm

regards,
Mike W.
 
The problem with using an EPROM like the 2716 is that some of the chip enable and output enable lines are the oposite polarity of the mask ROMS on the motherboard. Oddly the Applesoft and Integer BASIC rom cards had soler pads you could close that would make them work with 2716 EPROMSinteger-rom.jpg
 
I havn't looked at this much but it should be possible on some motherboards with extra empty solder pads for soldering cips for customization to solder a 74LS04 to invert the polarity of the ROM inhitbit lines comming from the slots. The picture is from my old Apple II (I have many now but this was my first). I believe it's a Rev B.

This would require cutting the line from the slots and runing it through the 74LS04 (invertor) then to the ROMS. You would need to replace all the ROMs with 2716's.apple-socket.jpg
 
After looking at my Apple II and consulting the Reference manual I have come to the conclusion that 2732 EPROMS would be easer to make work. On these pin 21 is just the high order adress line bit. You would only need route the INH line from the slots to the ROMS through a 74LS04 to make this work. All ROMs would need to be replaced with 2732's.apple-roms.jpg
 
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