Good news everyone, I've negotiated with the PH10x TAs, and they have agreed that it is OK if you come by the physics help desk for PH253 homework questions.* You can find the help desk hours here. The following TAs explicitly agreed to help with PH253 questions:
Lei Lu, Zachary Burell, Arindam Das, Jason Carson, Chockalingam Sivakumar, Sahar Keshavarz, Christopher Sterpka, Andrea Chaney
I didn't hear back from a few of the TAs when I asked if it was OK for you to come by, but the list above covers most of the available help desk hours. (I said that a lack of response would be construed as a 'yes' on their part though.) I agreed to send them the HW solutions in advance each week so they can better help you.
*Previously, the help desk was only for 100-level physics, but I asked if they would expand their repertoire.