[Hallicrafters] HT-37B Tube mystery

[Darryl Jones]

Hello All,

I recently picked up an HT-32B and am having problems identifying a missing tube. I pulled all the other tubes, and replaced any that my Hickock didn't like, but have yet to figure out what the missing tube is that wasn't on the chasis. It's located directly behind the tuning capacitor on that board, and doesn't have a chasis marking for it.

Anyone have an ID for me? 

Thanks for your help,
Darryl