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GND Loop Solution.md

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A GND Loop discovery from the older NES Revival Power Modules.

I first must express my appreciation for the Retro Community. Instead of tearing others down, they work to build and improve.
My mindset has always been that every design can be improved and I will always welcome any and all feedback.

A design flaw oversight was discovered from our power boards and community members brought this to my attention.
The original GND to NES location was placed near the Full Bridge Rectifier with the thought of having a short retun path.
My oversight was that the return path had to go all the way back to the Switching Regulator and then heads back to the rectifier.
This large GND Loop results in ringing and other undesirable impacts to the overall circuit.

While I do not believe that these power boards in the wild pose a danger to the NES, they will have a reduced life as a result.
Currently, I have only seen about a 4% failure rate on people reporting back to me. (Which I feel is still too high).
The whole idea behind this redesign from the beginning was to have a product that would last for years to come.

This GND Loop only impacts the Power Boards with Switching Regulators. It does not exist on the 7805 designs.
The suggestion for 2oz copper on the 7805 designs was to provide more copper for heat dissipation and not to couple noise frequencies.
I would like the express my thanks to the Dubesinhower Discord Group for bringing this to my attention.
I would also like to personally thank Zaxour for assisting with the new design layout. - https://twitter.com/zaxour

If you have one of these boards that has failed and have not yet contacted me. Please reach out so I can provide a full replacement at no cost.
To make right to the community that I love, I have 2 options for those that have a NES Revival Power Board and would like this fixed.

Option #1 - A quick DIY Fix to shorten the GND Loop on the Power Board itself

  • Step 1 Just right of the bottom interconnect pin, scrap back the soldermask
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  • Step 2 Place a ball of solder on this exposed GND section.
  • Step 3 Connect a GND Wire to that newly created pad and connect it to a nearby GND point on the NES Main Board
  • Step 4 Disconnect the original GNDing wire so that it's no longer on either the power module or the NES Main Board.

Option #2 - A replacement Power Module will be offered at a heavily discounted rate.

  • If you have spent money/resources in any of these designs and would like a full replacement. Please reach out to me.
  • My email is Merlin(dot)Shaw@gmail(dot)com. Let me know how many replacements you need to cover the boards you have made/purchased.
  • I will add your name to a list for replacements and will work to get through the list in a timely but realistic fashion.
  • The discount on the board will cover my costs and shipping.