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However, there are pin headers P207, P208, P209 and P210 next to the CPU, originally used to connect the memory daughterboard or a test system, that make it easy to add a small custom piggyback board with a decoder and a more modern E(E)PROM. An 8k×8 chip (2764, 2864) is sufficient to hold the 6kB needed for the DF2. As a bonus, this upgrades a DF1 to a DF2 if the missing front panel key is added as well (pads are present on the PCB). The stock ROM chips must be removed prior to installing the piggyback board. | However, there are pin headers P207, P208, P209 and P210 next to the CPU, originally used to connect the memory daughterboard or a test system, that make it easy to add a small custom piggyback board with a decoder and a more modern E(E)PROM. An 8k×8 chip (2764, 2864) is sufficient to hold the 6kB needed for the DF2. As a bonus, this upgrades a DF1 to a DF2 if the missing front panel key is added as well (pads are present on the PCB). The stock ROM chips must be removed prior to installing the piggyback board. | ||
<gallery> | |||
Tek DF1 DF2 ROM replacement board schematic.png | ROM piggyback board schematic (click to enlarge) | Tek DF1 DF2 ROM replacement board schematic.png | ROM piggyback board schematic (click to enlarge) | ||
Tek DF1 ROM_piggyback.jpg | Prototype | Tek DF1 ROM_piggyback.jpg | Prototype | ||
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</gallery> | </gallery> | ||
==Links== | ==Links== | ||
* [[Media:Tek DF1 ROM piggyback PCB.zip| ZIP file with EPROM image, Eagle BRD and SCH files for the ROM replacement board]] | * [[Media:Tek DF1 ROM piggyback PCB.zip| ZIP file with EPROM image, Eagle BRD and SCH files for the ROM replacement board]] designed by [[User:Peter|Peter]] | ||
[[Category:Instrument repair reports]] | [[Category:Instrument repair reports]] |