Tandy 1400FD PSUs
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The Tandy 1400FD had an external 12V 1.2A DC 'power brick', and an internal PSU that combined the PSU for the various voltages required by the computer and a battery charging circuit for the internal 4.8V NiCd battery pack in one internal unit. The unit has many electrolytic capacitors and is therefore very vulnerable to ageing.
External PSU
The external PSU provides 12V DC regulated output at 1.2A.
It is a simple design: a stepdown transformer full-wave rectified with four diodes and a couple of smoothing capacitors feed an STR9012 12V voltage regulator.
The internal fuse is 3.15A.
Internal PSU
Outputs
| Pin | Colour | Voltage/Purpose | Comments |
|---|---|---|---|
| 1 | White | 5V | - |
| 2 | Dark Blue | - | Reset? Jumps to 5V when machine is powered on, then declines to 0v quickly |
| 3 | Brown | 5V | - |
| 4 | Grey | 5V | - |
| 5 | Blue | - | 5V when on mains; 0V when on battery |
| 6 | Red | 12V | - |
| 7 | Purple | -12V | - |
| 8 | Orange | -22V | - |
| 9 | Black | GND | - |
| 10 | Black | GND | - |
| 11 | Black | GND | - |
| 12 | Black | GND | Feed to P2 (no feed from PSU) |
| 13 | n/c (key) | - | - |
| 14 | Green | 5V | Feed to P2 (no feed from PSU) |
| 15 | Pink | 5V | Maintained when on battery or mains |
| Pin | Colour | Voltage/Purpose | Comments |
|---|---|---|---|
| 1 | Black | GND | - |
| 2 | Green | 5V | - |
| Pin | Colour | Voltage/Purpose | Comments |
|---|---|---|---|
| 1 | Black | GND | - |
| 2 | Yellow | 5V | - |