Ok, I have committed latest batch of improvements. I have discovered I am somewhat OCD when it comes to having things lined up, oh well :)
I did a quick test of reverse polarity using the v1 A design. Applying 12V reversed to the board, both PSUs I used provide power very briefly then cut out due to overload. The 10A fuse did not blow, and there appeared to be no damage to the 1N4004. On testing with a meter though, the diode has failed short circuit, this seems to be a common failure mode for silicon diodes. I should really get a scope on and see how long power is applied.
I don't think we could rely on the diode failing short circuit. That and a combination of slow acting PTC is possibly a source of problems in RAMPS. Hopefully the new design should be more robust.
I had a choice between a TO277 package and DO214AB. They are about the same size, TO277 might be harder to solder as it has a pad under the chip, but seems to have a wider choice of parts although there is not a lot in it. I decided to go with the TO277.
I did a quick test of reverse polarity using the v1 A design. Applying 12V reversed to the board, both PSUs I used provide power very briefly then cut out due to overload. The 10A fuse did not blow, and there appeared to be no damage to the 1N4004. On testing with a meter though, the diode has failed short circuit, this seems to be a common failure mode for silicon diodes. I should really get a scope on and see how long power is applied.
I don't think we could rely on the diode failing short circuit. That and a combination of slow acting PTC is possibly a source of problems in RAMPS. Hopefully the new design should be more robust.
I had a choice between a TO277 package and DO214AB. They are about the same size, TO277 might be harder to solder as it has a pad under the chip, but seems to have a wider choice of parts although there is not a lot in it. I decided to go with the TO277.