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7D01/Repairs: Difference between revisions
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(Created page with "thumb|400px|right|Tek maintenance note for TI sockets issue (click to enlarge) The 7D01, DF1, and DF2 are often affected by '''bad TI I...") |
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==IC socket problem== | |||
The 7D01, [[DF1]], and [[DF2]] are often affected by '''[[bad TI IC sockets]]'''. | The 7D01, [[DF1]], and [[DF2]] are often affected by '''[[bad TI IC sockets]]'''. | ||
Tek eventually had to run an unpublicized board exchange program for those instruments due to the high failure failure rates. | Tek eventually had to run an unpublicized board exchange program for those instruments due to the high failure failure rates. | ||
==Bad ROMs== | |||
[[File:Tek DF1 ROM_piggyback.jpg|thumb|300px|right|Piggyback ROM board prototype in place (click to enlarge)]] | |||
Old mask ROM chips frequently fail, e.g. due to electromigration problems. Unfortunately, the DF1 CPU board uses 2k×8 ROMs with pre-JEDEC pinouts (see [[Mostek MK31000]]) so there are no easy in-socket replacements. The expansion ROM in the DF2 should be compatible with a 2516 EPROM. | |||
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 are removed. | |||
:''(schematic tba)'' | |||
[[Category:Instrument repair reports]] | [[Category:Instrument repair reports]] | ||