Some solder joints on the board are connected to large copper traces, these tend to be the high current traces. In these cases, it'll suck the heat away from the joint, into the copper, faster than normal, making to very difficult so get solder to flow into the still cold joint.
I tend to turn the heat up quite a bit, like 800F for the big components, like the two big diodes, and the MOV. Or generally any time I have a joint that's being a PITA. When you turn up the iron, give the iron a couple minutes to fully get up to temp, you need the tip good and heatsoaked so that it can dump it's heat into the joint. Make sure it's good and freshly tinned before you hit the joint, as at that temp, it burns the flux off the tinned tip pretty quickly.
The MS board is actually really good about this, they designed heat isolators around most of the big connections for this exact reason. I've dealt with other boards where it took nothing less than a 200watt soldering gun to get solder to flow into joints directly on the ground plane.
I tend to turn the heat up quite a bit, like 800F for the big components, like the two big diodes, and the MOV. Or generally any time I have a joint that's being a PITA. When you turn up the iron, give the iron a couple minutes to fully get up to temp, you need the tip good and heatsoaked so that it can dump it's heat into the joint. Make sure it's good and freshly tinned before you hit the joint, as at that temp, it burns the flux off the tinned tip pretty quickly.
The MS board is actually really good about this, they designed heat isolators around most of the big connections for this exact reason. I've dealt with other boards where it took nothing less than a 200watt soldering gun to get solder to flow into joints directly on the ground plane.
