From: Hessen, Germany - now living in France
Most sources say that the conversion to SST has been carried out during the overhaul at Mare Island, but I have come across two sites which claim that the decision to get rid of the minelaying gear was taken after the refit and Argonaut's return to Pearl Harbour.
I cannot relocate the first site I came across, but here is the second which seems to be well informed:
Contrary to some published reports, Barchet was not relieved for “lack of aggression” at the end of Argonaut‘s first war patrol. His executive officer, William Post, was sent to a staff job at Pearl Harbor and Argonaut‘s dive officer, Richard O’Kane was temporarily moved up to XO. Barchet then took the boat back to Mare Island for a much-needed refit and modernization. At that point, having commanded Argonaut since 1939, he turned over the boat to Lieutenant Commander John Pierce and O’Kane left to join the pre-commissioning crew of U.S.S. Wahoo. Barchet went on to serve in a number of important posts both during and after the war.
Still designated as a mine-layer upon her return to Pearl Harbor, the decision was made to convert Argonaut into a transport submarine. Her mine handling gear was removed and her mine tubes were cut out and blanked off at the after bulkhead, with the remaining sections outside the pressure hull pierced to allow them to be free-flooding. The space formerly allocated for mines was now filled with bunks, heads, mess facilities, and washroom. About 120 Marines could be accommodated. She was redesignated APS-1 after this conversion.