On Fri, Jul 12, 2024 at 11:12 PM, Dan Reynolds wrote:
If I unplug the 2x4 pin board there is an open and when I plug the board back in - it's a dead short.
Dan, so it looks like a problem related to this SMPS board.
On the VDD rail with the burnt power board installed there is a dead short on VDD.
Maybe the short comes from something burnt?
Her is a
document from the QRP Labs Wiki how to test the SMPS boards off line. The Wiki contains also documents about the
internal power supply and the
start up process.
I pushed the power encoder and a transistor on the 2x4 pin board lit up - literally and burnt. It was near the far end of the board by the big cap.?
I think it's Q108, the switching transistor to produce VCC. But this should not affect VDD. But there was also something with the VDD board (see No 4 in your post). So please check the two subboards off line first. I think both are not ok. In the moment I have no real idea how this would happen. Maybe you have unwanted connections related to the pin headers of the two SMPS subboards?
73, Ludwig
