Chuck,
I doubt you'll be able to find those Hoffman knobs. They may have used the same type knobs on their B&W models. So that may help you out. Use great care removing all the knobs and trim pieces. Try some super glue to save the broken knob. Be patient. Don't pry anything that's stuck. Put the knobs in some mild dish soap w/warm water. Let them soak and use a fine toothbrush to clean them up. The grille cloth may have to be a close match. Check with Radio Daze
www.radiodaze.com or Antique Electronic Supply
www.tubesandmore.com/. There are other suppliers on the net. Looks like the plastic shroud that covers your 21AXP22 is in bad shape. Another junker color set, if you can find one, using the 21AX may have a good one. Or you can replace the tube with a later 21" tube. This will present some new problems in mounting the later glass tube in this set as the plastic shroud is part of the mounting hardware and probably won't work with the later glass tubes. Have your tech friend advise you on this. Color sets of this era are far more complex then B&W 50's sets. WAIT for the SAMS before removing the picture tube. Or anything else chassis wise. Lots of connections, cables ect to remove before you even loosen the chassis bolts. I know you want to get right on this. But don't hurry this project. Good luck in your restoration. I hope your tech friend has experience in repairing these vintage color sets. Not many of this model color receiver stll around. Finally, here's an article on these sets posted on the ETF site: ETF - 1957 Hoffman Colorcasters
Address:
http://www.earlytelevision.org/hoffm...lorcaster.html Any other VKer's feel free to jump in on this.
-Steve D.