One thing I noticed about the filament wires going into the lamp. In the photos you have from PRIOR to the attachment of the outgoing filament wires (from the lamp to the first output tube), it appears as though the end of the lead (circled in a modification of your photo) going to the “tip” of the lamp holder may be touching the “sleeve” solder lug of the lamp holder. In the later photograph AFTER those outgoing leads to the output tube, you had rotated the lamp holder 180 degrees to allow the installation of the first giant filter cap, so I cannot see them in that photo. Unless you clipped off the protruding wire from the lead going to the “tip”, it may be touching the “sleeve” slug still – I can’t tell because it’s on the far side now, obscured by the lamp holder in the photo. If the two touch, maybe that’s why only one lead has 6.3 VAC on it? Just an idea to check. That of course does not explain the absence of HT DC coming off of pin 8 of the rectifier. Check your multimeter settings. Mine has separate voltage settings for DC voltage and AC voltage, which may make a difference in whether or not it detects and/or displays any voltage. Also, make sure that the correct pin numbers were used, since on the rectifier, the odd-numbered pins are not used. I can’t see the “index slot” in the tube socket in the photos, so I would merely suggest checking to make sure you did not accidentally rotate the wire locations by one pin in either direction, which would definitely cause the 5Y3 tube to not rectify. Or accidentally rotated the socket by 180 degrees. I attached a photo of the bottom of my chassis to show socket orientation, and a (sorry, blurry) photo of the rectifier connections while I was still in the process of building. Does its filaments glow at all? You’ve got the HT center-tap going to ground, so no issues there unless it’s a cold solder joint or something. I struggled soldering some of the connections due to tight clearances, but was fortunate enough not to melt any cap casings.