There's very little info online about how to get the preamp tubes out of an Engl amp. Here's a pic of the preamp tubes on my Savage 120:

How do I get those heat shields off? Do I just pull up, or do I have to twist?
You know you have to wear a lead-lined apron ( you can usually borrow one from a dentist) while removing these, right?
Har har. I called a local tube amp repair shop and they explained that you have to squeeze the sides of the heat shield to bring the two tabs in towards the tube, and they will lift out. I had to squeeze these things really hard to bring in those two outward metal tabs, and even then I had to bring up one side and then the other.

Good news: replacing the worn-out preamp tubes with some Sovtek 12AX7WBs brought the amp back to life. Great sounding amp.