So, you are getting continuity if you check from the HSTD lamp back to pin 23 on J2 of the LDB? You reflowed solder on that header? Clean out the sockets? I sometimes use a test socket and while in lamp test mode, touch the 2 leads to the leads of the socket having issues to see if it is a socket issue. Just a few other things off the top of my head. Try a different LDB to rule that out?