Serial Loopback Adapter

A serial loopback adapter is required when perform a serial loopback test in Amiga Test Kit.

Requirements

Female DB25 plug and (optionally) a case/hood.
Wires to join pins together.
Optional: LEDs and limiting resistors.

Build Instructions

Use the wires join the following pins together:

2 and 3
4, 5 and 6
8, 20 and 22

Optional:

For +12V, connected the negative side of the LED to pin 7 (GND), the positive side to a 1K resistor, and the other side of the resistor to pin 9 (+12V)
For -12V, connect the positive side of the LED to to pin 7 (GND), the positive side to a 1K resistor, and the other side of the resistor to pin 10 (-12V)

Below is a diagram to summarise how the pins and components are connected together:

Amiga Test Kit

When performing the serial loop back test, all the connected pins should GREEN.

A failed serial loop back test would have some RED on the pins:

Typically, a failed serial loopback test means that one or more of the serial chips (U38 and U39 on an A500/plus) has failed and needs to be replaced.