CA3146E transistor array (write driver) pinout
DIP-14. Head write driver and write/erase current switch
Five NPN transistors: a differential pair (Q1, Q2, common emitter pin 3) and three singles (Q3-Q5, Q5 emitter tied to the substrate at pin 13). On the Disk II card the pair switches current into the two halves of the center-tapped head through CR1 and CR2 as WR DATA toggles, and the other transistors switch the write current on with write request. Sams calls it the write amp. On Apple's chip-swap chart for I/O errors and for "reads but will not write".
Open the interactive 3146 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | Q1 C | io | Q1 collector: one half of the head winding through CR1. |
| 2 | Q1 B | io | Q1 base (differential pair input, write data). |
| 3 | Q1/Q2 E | io | Common emitter of the differential pair: the switched write current. |
| 4 | Q2 B | io | Q2 base (differential pair input). |
| 5 | Q2 C | io | Q2 collector: the other half of the head winding through CR2. |
| 6 | Q3 B | ctrl | Q3 base (write-current switch). |
| 7 | Q3 E | ctrl | Q3 emitter. |
| 8 | Q3 C | ctrl | Q3 collector. |
| 9 | Q4 B | ctrl | Q4 base. |
| 10 | Q4 E | ctrl | Q4 emitter. |
| 11 | Q4 C | ctrl | Q4 collector. |
| 12 | Q5 B | ctrl | Q5 base. |
| 13 | Q5 E / SUB | ground | Q5 emitter and the chip substrate; must be the most negative point (ground on this card). |
| 14 | Q5 C | ctrl | Q5 collector. |
Fitted in
- Disk II A3 on the analog card (socketed, Apple 351-3146)