I have a RapidRoad that I'd like to install into my Amiga 1200. Before I do - I have several A500 + A1200 power supplies, and I'd like to make sure I use the right one to avoid the CPLD latch-up problem. Is using a recapped 1200 power supply sufficient, or is there more I can do?
Pre-installation checks
- PacificState
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Don't Panic. Please wash hands.
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* add shield. The original one MUST be present (top and bottom), and all screws MUST be present and tightened.
* use the GND cable. Always. Never even try for a second without.
* NEVER use a clock-port expander.
* use the included power cable. Do not use a longer one.
* use the included clock port cable. Do not use a longer one.
* wire up an extra shield connection from the outer metal part of the USB connector to shield of your A1200.
* re-capped A1200 PSU may be OK, but a true self-powered hub may add more safety. If you have access to a CA-PSU, that will be best.
* When you're finished, re-check all shield connections. They must be mechanically wide, tight and "plenty", ideally surrounding the USB connectors, so a static zap goes into shield, not RapidRoad.
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is the latch-up caused by ESD?
Kind-of; indirectly. Whenever there is an event (hot-plug or static zap), the voltage regulators need to level it out. If the voltage on the power supply gets low, near the magical 4.85V threshold, the regulation overhead on the input side gets low, and regulation drifts into oscillation for a short period. This happens mostly with MeanWell-based PSUs (like A-Power, Elektroware and Keelog, as sold on Amazon), but also with any other PSU that's easily overloaded with lots of components inside an A1200. One way of reducing the probability of this oscillation is to keep GND paths really short and wide.
The observation is that the BigBox version does not suffer at all from the latch-up problem. On those machines, we have metal cases, short ground paths and screws that hold every grounded part close to the other. I will not guarantee it (as you may know, we're not making clock port devices any more, and service for these has ended early last year), but I'm sharing this info so you have a chance to do it better than unlucky others who thought that it's a great idea to remove all shielding and use plexi-cases (that's where most returns came from).
Since the clock port version requires you to use USB connectors "on a cable", you'll have to get creative to make another very short connection from the outer shield of these USB connectors to the shield of the computer.
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The last reply was more than 365 days ago, this thread is most likely obsolete. It is recommended to create a new thread instead.
