Mainboard 81-240
81-240A General Info
The 81-240A Mainboard was used for both the Kaypro II '83 and Kaypro 4 '83 machines. According to reports it detected if it was reading a single or double sided drive and would continue to function based on that data.
The previous board for the Kaypro II was the 81-110.
The universal board would replace it for the K2 '84 and K4 '84.
While the Q1 and it's resistor are silk screened on the board I have not seen them used on the 81-240. See the notes in Mainboard 81-110#Q1 for what this does.
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81-240A Machines
| Serial Num | Board Num | QC Sticker | Monitor ROM | Char ROM | Kaypro Model | Notes |
|---|---|---|---|---|---|---|
| #16679 | 30484 | none | 81-232 | 81-146 | KII No Model Num | Likely a FrankenKaypro due to multiple parts from multiple eras. Shield |
| #17083 | 53883 | M-681? | 81-232 | 81-146 | KII No Model Num | FrankenKaypro? Shield |
| #69691 | 14084 | 189-W | 81-232A | 81-146A | K4 81-004 | Shield |
| #76797 | 21658 | NLS FT 51? | 81-232A | 81-146A | KII 81-003 | Shield |
| #102622 | 20433 | 162-W | 81-232 | 81-146A | KII 81-003 | Shield |
| Loose board | 2980 | 81-232 | "CHAR V2.2 1992 D. Th? | |||
| Loose board | 29566 | 81-232A | 81-146A | Shield | ||
| Loose board | 29682 | 81-232 | 81-146 | Shield |
Mods for this board
On page 44 of the June-July edition of Micro Cornucopia there is an article about upgrading this motherboard to work with 256K. If your machine has an additional board with a 74LS393, 74LS158 and 74LS153 plus the 8 RAM chips have been replaced by 64K RAM chips then you likely have this mod. Click here for this Micro C