7404 / 74S04 hex inverter pinout
DIP-14. Six inverters; often used, with a crystal, as a clock oscillator
On the BBC Model B, IC43 is the 74S04 of the 16 MHz crystal oscillator, and the service manual photographs RAS on its pin 12. On the Electron (IC8) it runs both crystal oscillators. Pins 13-12, 11-10 and 9-8 with X1 (R1, R2 820R) make the 16 MHz clock, out on pin 8 to ULA pin 49, the 74LS169 and expansion pin 12. Pins 1-6 with X2 and trimmer VC1 make the 17.7345 MHz PAL subcarrier, out on pin 6 (TP1) to the 74S74 IC11; trim it to within 200 Hz. No 16 MHz = a dead machine; no 17.7 MHz = black and white on the TV only. Fit an S part, not LS.
Open the interactive 74S04 pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | 1A | io | Inverter 1 input. |
| 2 | 1Y | io | Inverter 1 output. |
| 3 | 2A | io | Inverter 2 input. |
| 4 | 2Y | io | Inverter 2 output. |
| 5 | 3A | io | Inverter 3 input. |
| 6 | 3Y | io | Inverter 3 output. |
| 7 | GND | ground | Ground. |
| 8 | 4Y | io | Inverter 4 output. |
| 9 | 4A | io | Inverter 4 input. |
| 10 | 5Y | io | Inverter 5 output. |
| 11 | 5A | io | Inverter 5 input. |
| 12 | 6Y | io | Inverter 6 output. |
| 13 | 6A | io | Inverter 6 input. |
| 14 | VCC | power | +5 V. |
Fitted in
- Acorn Electron IC8
- BBC Micro Model B IC43