About

Even with the new Mediator 1200 TX, the Amiga still does not receive the correct amount of power on the right traces such that any of the following symptoms may be observable:

  • there is no sound in games: there is some sound if you listen very carefully but the sound level is unbelievably low,
  • you may get very weird output with wrong hardware identifiers for the accelerator and the mediator when holding down both mouse buttons and selecting the Board Diagnosis menu item,
  • strange lockups and freezes as well as general instability

The Problem

The issue does not lie directly with the Mediator - Elbox support will claim that the Mediator works fine but that the motherboard seems to have issues with the $-12V$ power line which is just an incidental effect of the motherboard not being powered from its own power socket but rather through the accelerator adaptor.

The documentation for the Elbox BlackBox case does not refer to any way of powering the motherboard from its own socket claiming that the Mediator will provide power to the motherboard instead. Unfortunately, the Amiga motherboard does need the $-12V$ line to be powered from the socket that the Mediator cannot provide.

Fixing Elbox Mediator Power Issues

An easy fix that will withstand any future motherboard changes is to drill a hole in the Elbox BlackBox case and to mount a socket that will draw power from the unoccupied Mediator AT connector - since, most likely, the Mediator will be powered through the ATX connector.

The Elbox Mediator TX has two unused AT motherboard connectors: a P8 and a P9 for which we have the following pinouts:

Since the P9 AT connector does not include a $-12V$ lead, the P8 connector will be used instead:

The cable can then be pulled all the way down along or underneath the Mediator to the very bottom of the case:

The image shows the AT power lead wires soldered to the proper connections on a sliced Amiga power supply cable:

but this is just a temporary solution for testing.

A better solution is to use a 4 pin aviator plug and socket. A hole is drilled into the Blackbox tower case in order to fit the female aviator socket that is then fixed to the case using washers:

Finally, the Amiga power cable can be attached to male part of the aviator plug and secured in place using the fixing mechanism of the aviator plug with some additional heat-shrink tubing to make the cable resistant to torque:

The advantages of the modification is that the motherboard does not need to be modified and can even be exchanged for a different motherboard.

Testing

The immediate result will be that games will have their sound restored. Long term results may include more stability for both the motherboard and IO ports.


hardware/amiga/fixing_elbox_mediator_power_issues.txt ยท Last modified: 2022/04/19 08:28 by 127.0.0.1

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