ZX Spectrum IC25
The IC25 is a 74LS157 Logic IC and can be replaced with a modern 74HCT157 Logic IC
A modern replacement can be found here:
| Shop | Link |
|---|---|
| RetroRevivalShop | http://retrorevivalshop.co.uk/index.php?main_page=product_info&cPath=5&products_id=31 |
| Retroleum | https://www.retroleum.co.uk/zx-spectrum-chips |
Using a multimeter check the traces for IC25, the the diagram below for chip pin position
| Pin | Traces to | Voltage |
|---|---|---|
| 1 | IC26 Pin 1 | |
| 2 | IC3 Pin 2 | |
| 3 | IC3 Pin 3 | |
| 4 | Upper Ram (IC15-22) Pin 10 | |
| 5 | IC3 Pin 5 | |
| 6 | IC3 Pin 6 | |
| 7 | Upper Ram (IC15-22) Pin 11 | |
| 8 | IC24 Pin 7 | |
| 9 | Upper Ram (IC15-22) Pin 12 | |
| 10 | IC3 Pin 10 / IC2 Pin 33 | |
| 11 | IC3 Pin 11 / IC2 Pin 40 | |
| 12 | Upper Ram (IC15-22) Pin 13 | |
| 13 | IC3 Pin 13 | |
| 14 | IC3 Pin 14 | |
| 15 | IC3 Pin 15 | |
| 16 | IC3 Pin 16 |